Re: [bitcoin-dev] Packaged Transaction Relay

Re: [bitcoin-dev] Packaged Transaction Relay

[Eric Voskuil]

Thanks again for the feedback. Comments inline.

> On Sep 27, 2022, at 02:29, alicexbt <alicexbt@protonmail.com> wrote:
> 
> Hi Eric,
> 
> 
>> If by "range" you mean a connected tx subgraph, I don't see why not. But note that nodes only operate over signed txs. PSBT is a wallet workflow.
> 
> Matt Corallo mentioned that pre-signed transactions created with low fee rate become an issue when they are broadcasted after a long time and there is a high demand for block space at that moment.

Yes, I understood this. There are many ways that a fee may be created which is too low for propagation.

> Example: 
> 
> Bob created PSBT1 in a multi party contract with fee rate 5 sat/vbyte however its taking hours/days to confirm the transaction with such low fee rate.
> 
> Carol created PSBT1 (5 sat/vbyte), PSBT2 (10 sat/vbyte) and PSBT3 (20 sat/vbyte) for spending same inputs. She broadcasted PSBT3 which got confirmed in a few minutes. 
> 
> 
>> Always. Only signed transactions are accepted. But assuming you are referring to a transaction that has been produced by a pre-signing workflow, I'm not sure how this would be distinct from any other tx.
> 
> 
> `minfeefilter` for all peers of my node was 0.00001000 at the time of writing this email. I am assuming nobody creates pre-signed transaction with fee rate below 1 sat/vbyte. How often does it happen that `minfeefilter` is above this default value?

I don’t consider node configuration relevant, regardless of its apparent consistency.

>> I'm not sure I follow this, maybe you could reword it. But it seems that you are saying that CPFP fee-bumping is a problem scenario and the complexity of the proposed solutions are not justified by such scenarios.
> 
> 
> Sorry that sentence was confusing. Yes complexity isn't justified for CPFP fee-bumping txs below minimum fee rate.
> 
> 
>> There are many node implementations used presently. And of course these are protocol proposals, which presumes more than one implementation.
> 
> 
> Yes, a few implementations exist (knots, libbitcoin, btcd, bcoin etc.) however they aren't used by lot of nodes. Based on this [chart][1] 98% nodes use bitcoin core. Lot of bitcoin protocol proposals are influenced by bitcoin core contributors and things could be different if even 30% nodes used other implementations.

I don’t consider such a measure relevant. This is a protocol consideration. Also consider that many nodes are not visible, and aspects of nodes, such as for p2p communication, are embedded into applications such as wallets - which could easily exceed the number of visible nodes.

>> I don't consider this relevant to any protocol considerations. Miners should always be expected to select the most optimal set of txs available in the time available to do so.
> 
> 
> Agree, miners should be expected to select most optimal set of txs. However, according to one [comment][2] by Pieter Wuille, miners could affect the security of some bitcoin projects with MEV.

This would be a deficiency in such projects, by assuming economic irrationality. The fact that fees will become a greater percentage of the block reward is a surprise to no one.

>> Over time we are likely to see that the only policies that remain in widespread application are those that are necessary for DOS protection (fee rate), as other restrictions are not economically rational and cannot be enforced. We've seen recent debate regarding dust policy, and op_return policy. "non-standard" txs are perfectly valid but get stuck very easily. I'll reiterate, any policy beyond what is published via the protocol will cause the above problems.
> 
> I completely agree with this.
> 
> 
> [1]: https://luke.dashjr.org/programs/bitcoin/files/charts/software.html
> [2]: https://bitcoin.stackexchange.com/questions/107787/front-running-in-bitcoin#comment123441_107796
> 
> 
> /dev/fd0

Re: [bitcoin-dev] Packaged Transaction Relay

[eric]

> -----Original Message-----
> From: Anthony Towns <aj@erisian.com.au>
> Subject: Re: [bitcoin-dev] Packaged Transaction Relay
> > > > > > Protocol cannot be defined on an ad-hoc basis as a "courtesy"
> > > > > BIPs are a courtesy in the first place.
> > > > I suppose if you felt that you were the authority then this would
> > > > be your perspective.
> > > You seem to think that I'm arguing courtesy is not a good thing, or
> > > that we couldn't use more of it?
> > That is neither what I said nor implied. You were clearly dismissing
> > the public process, not advocating for politeness.
> 
> And that is neither what I said nor implied, nor something I believe. If
you
> think courtesy is something that can be ignored in a public process, I
don't
> think you should expect much success.

"BIPs are a courtesy in the first place."

> If you'd like to actually participate in public standards development,
please
> feel free to make some technical comments on my proposals, or others, or
> make your own proposal, either here or on github, or heck, anywhere else.

"RE: [bitcoin-dev] Packaged Transaction Relay"

> I mean, that's what I'd suggest anyway; I'm not your boss. I promise to at
> least be entertainingly surprised if you make any progress with your
current
> approach though.

Grow up Anthony.

e

Re: [bitcoin-dev] Packaged Transaction Relay

[Anthony Towns]

On Sun, Oct 09, 2022 at 12:00:04AM -0700, eric@voskuil.org wrote:
> On Sat, Oct 08, 2022, Anthony Towns via bitcoin-dev wrote:
> > > > > Protocol cannot be defined on an ad-hoc basis as a "courtesy"
> > > > BIPs are a courtesy in the first place.
> > > I suppose if you felt that you were the authority then this would be
> > > your perspective.
> > You seem to think that I'm arguing courtesy is not a good thing, or that
> we
> > couldn't use more of it?
> That is neither what I said nor implied. You were clearly dismissing the
> public process, not advocating for politeness.

And that is neither what I said nor implied, nor something I believe. If
you think courtesy is something that can be ignored in a public process,
I don't think you should expect much success.

If you'd like to actually participate in public standards development,
please feel free to make some technical comments on my proposals, or
others, or make your own proposal, either here or on github, or heck,
anywhere else.

I mean, that's what I'd suggest anyway; I'm not your boss. I promise to
at least be entertainingly surprised if you make any progress with your
current approach though.

Cheers,
aj

Re: [bitcoin-dev] Packaged Transaction Relay

[eric]

On Sat, Oct 08, 2022, Anthony Towns via bitcoin-dev wrote:
> > > > Protocol cannot be defined on an ad-hoc basis as a "courtesy"
> > > BIPs are a courtesy in the first place.
> > I suppose if you felt that you were the authority then this would be
> > your perspective.
> 
> You seem to think that I'm arguing courtesy is not a good thing, or that
we
> couldn't use more of it?

That is neither what I said nor implied. You were clearly dismissing the
public process, not advocating for politeness.

> > The BIP process was created by Amir specifically because Bitcoin
> > standards were being discussed and developed behind closed doors.
> 
> It definitely bothers me that Bitcoin development is not being discussed
out
> in the open as much as I would like, and to counter that, I try to
encourage
> people to post their ideas to this list, and write them up as a BIP; and
likewise
> try to do both myself as well.
> 
> But how much value do you think anyone's actually getting from posting
their
> development ideas to this list these days? Do you really think people
reading
> your mail will be more inspired to discuss their ideas in the open, or
that
> they'll prefer to get in a room with their friends and allies, and close
the
> doors so they can work in peace?

My comments have nothing to do with posting to this list.

> > > There's no central authority to enforce some particular way of doing
> > > things.
> > As if reaching consensus with other people implies a singular authority.
> 
> Reaching consensus with other people doesn't require putting a document in
> some particular github repo, either. Which is a good thing, or the people
in
> control of that repo would become that singular authority.

It is the public process that the community has clearly established. It has
been challenged at times, which anyone is free to do - creating their own if
they feel it becomes necessary. There is certainly no such issue in this
case, so it is not at all clear what you mean to imply here. Is this just a
blanket rejection of community standards development, or is it that you feel
this community is limited to "friends and allies"?

Developers of Bitcoin Core have stated countless times that they consider
Bitcoin Core to be the protocol documentation, implying that their internal
process is the process of arriving at community consensus. What was that you
said about "some particular github repo" becoming the "singular authority"?

> > > If you think that the version restriction should be part of the BIP,
> > > why not do a pull request? The BIP is still marked as "Draft".
> > I did not implement and ship a deviation from the posted proposal.
> 
> You think BIP 155 is suboptimal, and would rather see it changed, no?

The Bitcoin Core developers who deployed the deviation apparently also
thought the BIP was suboptimal. Whether I agree with the change isn't
relevant.

> But if you won't put any effort into changing it (and how much effort do
you
> think a PR to change it document it as being gated by version 70016 would
> be?), why do you imagine the people who are happy with the BIP as it is
> would put any effort in?

Yes, that's it. I'm lazy. It's all about effort, not about the process
which, by your own measure, the owners of a single repo aim to be the
"singular authority".

> > > > I doubt that anyone who's worked with it is terribly fond of
> > > > Bitcoin's P2P  protocol versioning. I've spent some time on a
> > > > proposal to update it, though it hasn't been a priority. If anyone
> > > > is interested in collaborating on it please contact me directly.
> 
> "contact me directly" and wanting something other than standards "being
> discussed and developed behind closed doors" seems quite contradictory to
> me.

It's the public process that is at issue, and you of course know that -
hence your varied attempts here to make it about something else.

> > Your contributions notwithstanding, you are in no place to exhibit
> > such arrogance.
> 
> I don't understand what you think is arrogant about posting a public
proposal
> about how I think things should work, even if I had only put
> 10 minutes thought into it. If that *is* arrogance, I guess I think we
could use
> more of it, as well as more courtesy...

As if I was referring to this.

"BIPs are a courtesy in the first place" says it all.

Best,
e

Re: [bitcoin-dev] Packaged Transaction Relay

[Anthony Towns]

On Sat, Oct 08, 2022 at 12:58:35PM -0700, Eric Voskuil via bitcoin-dev wrote:
> > > Protocol cannot be defined on an ad-hoc basis as a "courtesy"
> > BIPs are a courtesy in the first place.
> I suppose if you felt that you were the authority then this would be your
> perspective. 

You seem to think that I'm arguing courtesy is not a good thing, or that
we couldn't use more of it?

If it helps: courtesy is a good thing, and we could use more of it.

> The BIP process was created by Amir specifically because Bitcoin standards
> were being discussed and developed behind closed doors.

It definitely bothers me that Bitcoin development is not being discussed
out in the open as much as I would like, and to counter that, I try to
encourage people to post their ideas to this list, and write them up as
a BIP; and likewise try to do both myself as well.

But how much value do you think anyone's actually getting from posting
their development ideas to this list these days? Do you really think
people reading your mail will be more inspired to discuss their ideas
in the open, or that they'll prefer to get in a room with their friends
and allies, and close the doors so they can work in peace?

> > There's no central authority to enforce some particular way of doing
> > things.
> As if reaching consensus with other people implies a singular authority.

Reaching consensus with other people doesn't require putting a document
in some particular github repo, either. Which is a good thing, or the
people in control of that repo would become that singular authority.

> > If you think that the version restriction should be part of the BIP,
> > why not do a pull request? The BIP is still marked as "Draft".
> I did not implement and ship a deviation from the posted proposal.

You think BIP 155 is suboptimal, and would rather see it changed, no?

But if you won't put any effort into changing it (and how much effort do
you think a PR to change it document it as being gated by version 70016
would be?), why do you imagine the people who are happy with the BIP as
it is would put any effort in?

> > > I doubt that anyone who's worked with it is terribly fond of Bitcoin's
> > > P2P  protocol versioning. I've spent some time on a proposal to
> > > update it, though it hasn't been a priority. If anyone is 
> > > interested in collaborating on it please contact me directly.

"contact me directly" and wanting something other than standards "being
discussed and developed behind closed doors" seems quite contradictory
to me.

(In my opinion, a big practical advantage of doing things in public is
that it's easy for people to contribute, even if it's not a particular
priority, and that it's also easy for someone new to take over, if the
people previously working on it decide they no longer have time for that
particular project)

> > Bottlenecking a proposal on someone who doesn't see it as a priority
> > doesn't seem smart?
> I didn't realize I was holding you up. As far as I've been able to gather,
> it hasn't been a priority for anyone. Yet somehow, on the same day that I
> posted the fact that I was working on it, it became your top priority.

It's not my top priority; it's just that writing a BIP and posting
it publicly is fundamentally no harder than writing an email to
bitcoin-dev. So since I'm willing to do one, why waste anyone's time by
not also doing the other? Would've been even easier if I'd remembered
Suhas had already written up a draft BIP two years ago...

And if I'm going to suggest you should post a patch to a BIP you think
is flawed, then not drafting a BIP to improve on a practice I think is
flawed would be pretty hypocritical, no?

(I didn't read what you said to imply that you were working on it,
just that you'd spent time thinking about it, were interested, and
might do more if people contacted you. If you have been working on
it, why not do so in public? You already have a public bips fork at
https://github.com/evoskuil/bips/branches -- how about just pushing your
work-in-progress there?)

(Ah, I also see now that I did contact you in Dec 2020/Jan 2021 on this
topic, but never received a response. Apologies; the above was meant as
a general statement in favour of just collaborating in public from the
start for the practical advantages I outline above, not a personal dig)

> > Here's what I think makes sense:
> > https://github.com/ajtowns/bips/blob/202210-p2pfeatures/bip-
> > p2pfeatures.mediawiki
> Looks like you put about 10 minutes of thought into it. In your words, BIPs
> are a courtesy - feel free to do what you want.

So, you wrote a lot of stuff after this, but unless I missed it, it
didn't include any substantive criticism of the proposal, or specific
suggestions for changing it, or even any indication why you would have
any difficulty supporting/implementing it in the software you care about.

> Your contributions notwithstanding, you are in no place to exhibit such
> arrogance.

I don't understand what you think is arrogant about posting a public
proposal about how I think things should work, even if I had only put
10 minutes thought into it. If that *is* arrogance, I guess I think we
could use more of it, as well as more courtesy...

(I mean, if I *had* only spent 10 minutes on it then posting it to the
list might be a waste of everyone else's time; but I could still put it in
my bips fork, and blog/tweet about it, or mention it on irc or similar,
which is at least still a public proposal. And in this case I've been
thinking about it on and of since 2020, and do know that other people
share similar views, so I don't think it's wasting people's time)

Cheers,
aj

Re: [bitcoin-dev] Packaged Transaction Relay

[eric]

> From: Anthony Towns <aj@erisian.com.au>
> On Wed, Oct 05, 2022 at 09:32:29PM -0700, Eric Voskuil via bitcoin-dev
wrote:
> > Protocol cannot be defined on an ad-hoc basis as a "courtesy"
> 
> BIPs are a courtesy in the first place.

I suppose if you felt that you were the authority then this would be your
perspective. However in the case of community software development, open
standards are a tool to preempt such centralization.

The BIP process was created by Amir specifically because Bitcoin standards
were being discussed and developed behind closed doors. That process was
being funded almost entirely by a corporate consortium (the Bitcoin
Foundation). It was also clear that one implementation leads directly to
this type of authority complex, which is why he also started libbitcoin.
It's not surprising to learn that you feel this way, and it's nice of you to
share those thoughts publicly.

> There's no central authority to enforce some particular way of doing
things.

As if reaching consensus with other people implies a singular authority.

> > - and it's not exactly a courtesy to keep yourself from getting dropped
by
> peers. It is not clear to me why such a comment would be accepted instead
> of specifying this properly.
> 
> If you think that the version restriction should be part of the BIP, why
not do
> a pull request? The BIP is still marked as "Draft".

I did not implement and ship a deviation from the posted proposal. The
developers who did so spent almost as much time writing a comment about the
intentional deviation as they would have spent issuing a PR to the BIP.
Presumably, given that years have passed, there has been enough time to
correct that "mistake". At this point there are at least 5 implementations
operating on mainnet that are inconsistent with Core.

> > I doubt that anyone who's worked with it is terribly fond of Bitcoin's
P2P
> protocol versioning. I've spent some time on a proposal to update it,
though
> it hasn't been a priority. If anyone is interested in collaborating on it
please
> contact me directly.
> 
> Bottlenecking a proposal on someone who doesn't see it as a priority
doesn't
> seem smart?

I didn't realize I was holding you up. As far as I've been able to gather,
it hasn't been a priority for anyone. Yet somehow, on the same day that I
posted the fact that I was working on it, it became your top priority.

> Here's what I think makes sense:
> 
> https://github.com/ajtowns/bips/blob/202210-p2pfeatures/bip-
> p2pfeatures.mediawiki

Looks like you put about 10 minutes of thought into it. In your words, BIPs
are a courtesy - feel free to do what you want.

I'm well aware of your contributions to Bitcoin, but I find the arrogance
off-putting. I have spent many years contributing to Bitcoin development and
understanding, entirely on my own dime, even paying others to do so - as
well as raising donations for them. I do this intentionally, not because
I/we haven't had offers. Many corporate and state-funded Bitcoin Core
developers have repeatedly, aggressively, openly and self-servingly worked
to put a stop to such community efforts. To them the BIP process is a
"courtesy" - just sometimes documenting what they happen to be doing in the
protocols. And without actual alternatives, that's exactly what it is.

So I'll just leave you with this:

"MIT Digital Currency Initiative (DCI) announces research collaboration with
the Bank of England on central bank digital currency

The Bank of England announced an agreement to collaborate on a twelve-month
Central Bank Digital Currency (CBDC) research project with MIT Digital
Currency Initiative. The agreement supports and builds on DCI's ongoing
research into CBDC, while also contributing to the Bank of England's wider
research and exploration of central bank digital currencies. While no
decision has been made on whether or not to introduce a CBDC in the UK, the
work will investigate and experiment with potential CBDC technology designs
and approaches, and evaluate key tradeoffs, opportunities, and risks. This
type of research can help inform wider policy development by contributing
important technical ideas and questions. 

As part of OpenCBDC, DCI's open-source codebase and research initiative, MIT
DCI aims to fill this gap by engaging technologists, user researchers,
central bankers, private sector leaders, and academics in service of a more
accessible, trusted, fair, and resilient economy. We don't yet know if or in
what contexts CBDCs can help improve the broader international monetary
system, or how they might be best designed to do so, but we believe engaging
in technical research is an important step in answering these questions."

https://dci.mit.edu/research/2022/3/31/mit-digital-currency-initiative-dci-a
nnounces-research-collaboration-with-the-bank-of-england-on-central-bank-dig
ital-currency

https://ras.mit.edu/finding-funding/find-funding/federal-funding

https://dci.mit.edu/anthony-aj-towns

Some might call this a conflict of interest. A widespread community of
independent implementations is not in the interest of those who both make
and must comply with regulatory diktat.

Then of course there's this:

"Joichi Ito, director of MIT's Media Lab, resigned Saturday (Sept. 7 [2019])
after The New Yorker published an investigation into his attempts to conceal
financial contributions from pedophile Jeffrey Epstein. Although Ito
stewarded MIT's lab, his work and legacy in the crypto community have
largely passed under the radar.

Ito established the Digital Currency Initiative (DCI) at MIT, helping
bitcoin survive some of its darkest days in 2015. That year, when the
Bitcoin Foundation, a nonprofit dedicated to the cryptocurrency's
development faced "funding constraints," the DCI welcomed bitcoin core
developers Gavin Andresen, Cory Fields, and Wladimir van der Laan in
full-time roles."

https://qz.com/1704325/revisiting-mits-digital-currency-initiative-after-joi
-ito-epstein/

DCI jumps in to "help Bitcoin survive some of its darkest days". What
exactly was dark about these days apart from the fact that this corporate
consortium fell apart? It fell apart due to widespread community rejection -
initially driven by Amir. What fell apart was the attempt at corporate
influence/control, with development largely driven by Gavin and Mike Hearn
on the payroll - both of whom eventually disgraced themselves.

Your contributions notwithstanding, you are in no place to exhibit such
arrogance.

Best,
e

> Cheers,
> aj

Re: [bitcoin-dev] Packaged Transaction Relay

[Anthony Towns]

On Wed, Oct 05, 2022 at 09:32:29PM -0700, Eric Voskuil via bitcoin-dev wrote:
> Protocol cannot be defined on an ad-hoc basis as a "courtesy"

BIPs are a courtesy in the first place. There's no central authority to
enforce some particular way of doing things.

> - and it's not exactly a courtesy to keep yourself from getting dropped by peers. It is not clear to me why such a comment would be accepted instead of specifying this properly. 

If you think that the version restriction should be part of the BIP,
why not do a pull request? The BIP is still marked as "Draft".

> I doubt that anyone who's worked with it is terribly fond of Bitcoin's P2P protocol versioning. I've spent some time on a proposal to update it, though it hasn't been a priority. If anyone is interested in collaborating on it please contact me directly.

Bottlenecking a proposal on someone who doesn't see it as a priority
doesn't seem smart?

Here's what I think makes sense:

https://github.com/ajtowns/bips/blob/202210-p2pfeatures/bip-p2pfeatures.mediawiki

Cheers,
aj

Re: [bitcoin-dev] Packaged Transaction Relay

[eric]

>> ...sendaddrv2 messages are only sent to nodes advertising version 70016 or later (same as wtxidrelay)

> I don’t see this constraint in BIP155. Do you mean that addrv2 support was
> released in Core at the same time as wtxidrelay, or that it is an
> undocumented version constraint implemented in Core?

I see that it is the latter:

// BIP155 defines addrv2 and sendaddrv2 for all protocol versions, but some
// implementations reject messages they don't know. As a courtesy, don't send
// it to nodes with a version before 70016, as no software is known to support
// BIP155 that doesn't announce at least that protocol version number.

https://github.com/bitcoin/bitcoin/pull/20564/files#diff-6875de769e90cec84d2e8a9c1b962cdbcda44d870d42e4215827e599e11e90e3R2366-R2370

The version string in the log message I posted implies it may not be a Core release. Yet it is BIP155 compliant.

Protocol cannot be defined on an ad-hoc basis as a "courtesy" - and it's not exactly a courtesy to keep yourself from getting dropped by peers. It is not clear to me why such a comment would be accepted instead of specifying this properly. A new protocol cannot define a message for "all versions", it can only assume that older versions will disregard all unknown message traffic - or that implementers will patch it in this ad-hoc matter.

I would suggest that authors update BIP155 and BIP330 (both still in Draft status), as well any pending proposals that may have picked up this pattern from BIP155.

I doubt that anyone who's worked with it is terribly fond of Bitcoin's P2P protocol versioning. I've spent some time on a proposal to update it, though it hasn't been a priority. If anyone is interested in collaborating on it please contact me directly.

e

Re: [bitcoin-dev] Packaged Transaction Relay

[Eric Voskuil]

>> [Regarding bandwidth waste: I've pointed out in years past that
>> breaking the Bitcoin versioning scheme creates a requirement that any
>> unknown message type be considered valid. Up until a recently-deployed
>> protocol change, it had always been possible to validate messages by
>> type. I noticed recently that validating nodes have been dropping peers
>> at an increasing rate (a consequence of that deployment). Despite being
>> an undocumented compatibility break, it is now unfortunately a matter
>> of protocol that a peer must allow its peers to waste its bandwidth to
>> remain compatible - something which we should eliminate.]
> 
> The only message listed as not being preceded by a bumped version number
> in:
> 
> https://github.com/libbitcoin/libbitcoin-network/wiki/Protocol-Versioning

Good find, still a work in progress.

> is addrv2 (though addrv2 is gated on mutual exchange of sendaddrv2, so
> it's presumably the sendaddrv2 message at issue),

addrv2 is listed as the BIP title, the message that would cause the break is sendaddrv2 (quoted text).

> however since [0]
> sendaddrv2 messages are only sent to nodes advertising version 70016 or
> later (same as wtxidrelay).

I don’t see this constraint in BIP155. Do you mean that addrv2 support was released in Core at the same time as wtxidrelay, or that it is an undocumented version constraint implemented in Core?

> ADDRV2 was introduced May 20 2020 after the
> 0.20 branch, and SENDADDRV2 gating was merged Dec 9 2020 and included
> from 0.21.0rc3 onwards.

To clarify, there was no Core release of addrv2 without sendaddrv2 apart from 0.21 release candidates?

> [0] https://github.com/bitcoin/bitcoin/pull/20564
> 
> I'm only seeing "bytesrecv_per_msg.*other*" entries for nodes advertising
> a version of 0.17 and 0.18,

> which I presume is due to REJECT messages (for taproot txs, perhaps?).

Ideally you should not be seeing reject messages as protocol “other”, as these are valid messages as of protocol version 70002, and they are excluded by negotiated version before that. While there is no requirement to send them (BIP61 only defines a new message type), they remain defined messages until removed by a future protocol version.

> Otherwise, I don't think there are any unexpected
> messages you should be receiving when advertising version 70015 or lower.

Yet nodes with an advertised protocol version of 70013 are receiving sendaddrv2. I've removed the IP address from the log extract below.

17:53:45.022347 DEBUG [network] Peer [x.x.x.x:8333] protocol version (70016) user agent: /Satoshi:0.21.0()/
17:53:45.022377 DEBUG [network] Negotiated protocol version (70013) for [x.x.x.x.135:8333]
17:53:45.022767 INFO [network] Connected outbound channel [x.x.x.x.135:8333]
17:53:45.022913 DEBUG [node] Ask [x.x.x.x:8333] for headers after [00000000000000000002e8c1c59fc86f721ba3a3294d2b1165597ddb910058e6]
17:53:45.023184 WARNING [network] Invalid sendaddrv2 payload from [x.x.x.x:8333] object does not exist
17:53:45.023317 DEBUG [network] Stop protocol version on [x.x.x.x:8333] object does not exist
17:53:45.023359 DEBUG [network] Outbound channel stopped [x.x.x.x:8333] success

To my knowledge the only other time we've seen consistent invalid message traffic on the network was during the work on BIP150 (withdrawn), at which point BIP150 nodes were being deployed on mainnet. I made comments here on the issue at the time, which as I recall were generally rejected in favor of forcing nodes to allow all invalid traffic. In any case BIP150 was withdrawn and BIP324 proposed, which fixes this particular issue (using a service bit).

Some argued at the time that allowance for invalid messages was a longstanding requirement in the protocol. I knew that this was not the case (except for BIP37, break documented in BIP60) because libbitcoin validates all messages, which led me to eventually document it. Recently I updated and posted that documentation (the github wiki link you found). This was a consequence of reviewing the Generic Package Relay proposal, which is also incompatible. In doing so I noticed this issue with BIP155 and BIP330 as well. This led us to check the logs for peer disconnects as a result of invalid messages, at which point the above was found to be an increasingly common occurrence.

Best,
e

> Cheers,
> aj

Re: [bitcoin-dev] Packaged Transaction Relay

[Anthony Towns]

On Tue, Oct 04, 2022 at 05:01:04PM -0700, Eric Voskuil via bitcoin-dev wrote:
> [Regarding bandwidth waste: I've pointed out in years past that
> breaking the Bitcoin versioning scheme creates a requirement that any
> unknown message type be considered valid. Up until a recently-deployed
> protocol change, it had always been possible to validate messages by
> type. I noticed recently that validating nodes have been dropping peers
> at an increasing rate (a consequence of that deployment). Despite being
> an undocumented compatibility break, it is now unfortunately a matter
> of protocol that a peer must allow its peers to waste its bandwidth to
> remain compatible - something which we should eliminate.]

The only message listed as not being preceded by a bumped version number
in:

https://github.com/libbitcoin/libbitcoin-network/wiki/Protocol-Versioning

is addrv2 (though addrv2 is gated on mutual exchange of sendaddrv2, so
it's presumably the sendaddrv2 message at issue), however since [0]
sendaddrv2 messages are only sent to nodes advertising version 70016 or
later (same as wtxidrelay). ADDRV2 was introduced May 20 2020 after the
0.20 branch, and SENDADDRV2 gating was merged Dec 9 2020 and included
from 0.21.0rc3 onwards.

[0] https://github.com/bitcoin/bitcoin/pull/20564

I'm only seeing "bytesrecv_per_msg.*other*" entries for nodes advertising
a version of 0.17 and 0.18, which I presume is due to REJECT messages (for
taproot txs, perhaps?). Otherwise, I don't think there are any unexpected
messages you should be receiving when advertising version 70015 or lower.

Cheers,
aj

Re: [bitcoin-dev] Packaged Transaction Relay

[eric]

> Hi,
> 
> Thanks for sharing your thoughts on packaged transaction relay.

Hello, thanks for the reply.

>> The sole objective, as expressed in the OP proposal, is to:
>> "Propagate transactions that are incentive-compatible to mine, even
>> if they don't meet minimum feerate alone."
> 
> I actually do think there are additional goals we should include in any protocol
> change involving transaction relay, such as ensuring that we minimize
> bandwidth waste as much as possible (as I mentioned in a previous message
> in this thread).

Yes - there is always the presumption of an optimally-performing protocol (not limited to bandwidth), this is just a restatement from the OP.

The OP fails to eliminate orphan announcement, fails to prevent packages with insufficient fee from getting stuck in the same manner as txs (without explicitly re-announcing them again in an even larger package of higher feerate), and results in orphaned package announcements for the same reason (a static package is effectively just a larger tx).

Due to the resulting orphaning, a node must allow its peer to continue to broadcast unverifiable orphans to it, potentially chasing ancestry. So in addition to bandwidth waste, there is also an inherent problem of bandwidth DOS. These are problems specifically addressed by packaged relay.

[Regarding bandwidth waste: I've pointed out in years past that breaking the Bitcoin versioning scheme creates a requirement that any unknown message type be considered valid. Up until a recently-deployed protocol change, it had always been possible to validate messages by type. I noticed recently that validating nodes have been dropping peers at an increasing rate (a consequence of that deployment). Despite being an undocumented compatibility break, it is now unfortunately a matter of protocol that a peer must allow its peers to waste its bandwidth to remain compatible - something which we should eliminate.]

> While I understand your proposal seeks to improve on an idea of static
> packages in favor of dynamic package construction based on knowledge a
> node should have of its peers, I think the main drawback of your proposal is
> that it doesn't take into account the complexities of what a peer's "minimum
> feerate" might mean. The consequence of this is that it's not generally
> possible for a node to accurately guess whether a given transaction should
> be sent in a package to a given peer, or not, and so in addition to any
> "packaged transaction relay" mechanism that is implemented by a
> transaction announcer, we'd still need to add protocol support for a receiving
> peer to retrieve a package as well.

It is certainly possible that there is ambiguity in BIP133 (and BIPs that modify it). However it's not clear to me which such ambiguity you are referring to. There is no guessing proposed.

> First of all, a node's feerate is a dynamic value.  BIP 133 allows for nodes to
> send feefilter messages at any time during the lifetime of a peer connection.
> If we were to compare the feerate of ancestors of a relayed transaction to
> the feerate in place at a peer as indicated by feefilter messages, and use that
> determine whether those ancestors would have been successfully relayed or
> not, then doing so accurately would seem to require caching relay success for
> each transaction, for each peer, at the time such transaction is relayed (or
> perhaps caching feefilter values that are received from a peer?).  This seems
> likely to be undesirable,

This is a possible implementation. What makes it undesirable?

> and, at any rate, is more complex than merely comparing a pair of feerates.

There are no necessary protocol changes (though a new INV type is ideal), so the relative complexity you are implying could only arise from implementation. While implementation considerations are relevant, achieving simplicity in the protocol is presumably the priority. Further, implementation complexity must be considered from what is necessary to actually achieve the objectives, and not from the perspective of any given implementation.

Merely comparing a pair of feerates produces the problems described above, which includes not resolving the central problem, so this is an apples-to-oranges comparison. It's also more complex than doing nothing, but that also doesn't resolve the problem.

> But even more fundamental than feerates being dynamic is that feerate
> itself is not a well-defined concept when applied to arbitrary transaction
> (sub-)graphs, and this is at the crux of the difficulty in coming up with
> proposals that would meet the objective of ensuring that transactions which
> are incentive-compatible to mine all get relayed successfully across the
> network.  Here are a couple examples that illustrate this:
> 
> - Let A be a low feerate transaction (below any peer's minimum feerate).  Let
> B and C be descendants of A (but are otherwise unrelated).  Suppose these
> transactions are relayed to a node in the order A, B, C.  In the algorithm you
> proposed, I believe the determination for whether C should be announced
> to a given peer as a package (A, C) or as a singleton would either (1) depend
> on whether the package (A, B) was sufficient to meet the peer's feerate,

Yes

> or (2) waste bandwidth by engaging in packaged relay whenever A was already
> successfully relayed as part of a package.  Both of these approaches seem
> undesirable.
> 
> - Let A be a high fee, but low feerate transaction.

Low feerate means low fee (as high/low can only be relative to size), it's not clear how these can both be true.

>  Suppose B is a transaction
> that conflicts with A, has a high feerate, but lower total fee.  In this situation,
> two different nodes that learned of these two transactions in opposite order
> [(A, B) vs (B, A)] might be expected to have differing mempools -- this at
> least would be the case in the BIP 125 algorithm (which requires that both
> feerate and total fee must increase when replacing an existing transaction),

As a node knows which txs it has relayed to its peer, order of arrival is inconsequential.

> and at any rate it's not obvious from the information given which would be
> more optimal to include in a block, as that depends on factors that go beyond
> just these two transactions. 

Block inclusion in not pertinent, either may be included.

> Suppose further that a new transaction C is
> relayed on the network, which is a child of B and very high feerate, such that
> B + C have higher fee and higher feerate than A, when taken together.  In
> this case we'd want our relay protocol to ensure that even nodes which saw
> A first should still have a chance to consider transaction C, but the packaging
> design you propose (which would compare transaction B's feerate to the
> peer's, and conclude packaging is unnecessary because B's feerate might
> already exceed the peer's feerate) would not facilitate this.

Given that A and B are conflicts, A and B+C are conflicts. This is no different than the original conflict of A and B, and decided based on the required BIP125 fee increment. If A arrives first, B must be an increment over A, and vice versa. Upon the arrival of C, given prior acceptance of both A and B, B+C must be an increment over A, as the conflict arises from A/B.

> To summarize, the point I'd make from these examples is that we should not
> expect that "feerate" (whatever that means) alone will be a sufficient
> predictor of what is in our peer's mempools.

Predicting a peer's set of confirmable transactions ("mempool") is not the objective or a requirement. As far as I can tell it is sufficient to achieve requirements to the extent there are no unpublished policies.

Upon startup and connection to a peer, a node may have an empty mempool. In this case there will be no orphan or redundant announcements from the peer.

A node with a populated mempool may connect to a peer. In that case the peer will receive announcements from the peer for txs which it may already have. This will also occur due to multiple peer connections. Redundancy is not within the scope of this or the OP proposals (there are other proposals for limiting this redundancy in both scenarios to the extent desirable).

Once a node has been connected to the network for some amount of time, there will be no orphans or connection-specific redundancies announced to it. This provides a basis for the node to drop non-conforming peers (that support packaged relay), improving protection against bandwidth-wasting peers.

Any node which implements unpublished policies can expect to receive orphan announcements. This raises the question of whether the protocol should incorporate a facility for such a node to chase down orphans in the case where it is orphaning them by deleting their ancestors, even though it publishes that it accepts them based on feerate/rbf. This would imply that there is some other discretionary aspect of transactions that, as a matter of protocol, should be considered for relay.

Any such aspect internal to a tx would be economically-irrational to consider (which includes censorship), in which case it would seem preferrable to let such nodes simply accept the fact that they are creating orphans for themselves.

Any such aspect external to the tx would also be economically-irrational (mining wants the greatest possible fee opportunity), but may be a consequence of resource limitations. Storing confirmable txs in RAM constrains such resources by orders of magnitude, and an assumption that an implementation must do this would be an error (some do not). Yet storage remains finite, so this remains a possible though marginal consideration given the presumption that all accepted txs are both confirmable and satisfy feerate/rbf policy. In the case where a node is discarding previously accepted and yet-unconfirmed txs, the node accepts the possibility that this will result in it receiving orphan announcements.

The rational way to reduce the size of the mempool is to raise the published feerate, discarding txs that no longer conform. While this was not specifically described in the fairly informal proposal, the receipt of a reduced peer feerate message can cause a node to update its state for that peer, eliminating the possibility of orphan announcements to it.

>  So while there may be some
> situations where a transaction relayer might be able to usefully package up a
> transaction with its dependencies (perhaps in narrowly defined situations),
> there will also always be situations where this isn't possible, and what I
> conclude from that is that it should be helpful to add to the protocol some
> way for the recipient of a transaction to request the dependencies directly.

I don't think this has been shown, but finding such issues is of course why we discuss it.

> Taken together, I roughly understand Gloria's efforts here to be a
> combination of these two approaches: add some amount of packaged
> transaction relay for simple cases (ie where the transaction graph has been
> sufficiently narrowed, to minimize bandwidth waste while reducing latency),
> and also allow for a fallback mechanism where the recipient of a transaction
> can efficiently retrieve dependencies.  There seems to be a tradeoff
> involving latency, bandwidth, and robustness of these two approaches (and
> maybe also implementation complexity), so I think it's natural to expect that
> it will take some discussion and understanding of what practices are common
> on the network and what behaviors wallet or other software might adopt,
> given potential protocol changes, to figure out how best to balance these
> ideas.

The problems that I see with static packaging are:

1) Does not fully resolve the problem - a static package itself can get stuck for the same reason as a tx.
2) Requires wallet formation of a static packages - to resolve what is fundamentally a network issue.
3) Adds a complex new protocol to achieve what can be accomplished with almost no protocol change.
4) Is not bandwidth optimal, as it continues to relay/chase orphans (singular and packaged).
5) Is not DOS optimal, as it requires allowance for orphans and redundancies.

Regarding complexity - searching and marking a DAG is basic CS, and there isn't much else to the necessary implementation. There are no new messages, just a version bump and a preferably a new INV type. In terms of performance and therefore any possible increase to relay latency, this is easily measured in terms of complexity. Whether this would be a latency increase or decrease in relation to the OP is unclear.

The complexity of the search for is linear in the size of the mempool subgraph (1) induced by the traversal of ancestors from the potential package's last tx, and (2) reduced by the set of txs known to the peer. (2) includes both txs sent to and received from the peer. This would appear to be a marginal cost.

A draft of the search algorithm is available here:

https://github.com/libbitcoin/libbitcoin-network/wiki/Iterative-Channel-Package-Computation

Best,
e

Re: [bitcoin-dev] Packaged Transaction Relay

[Suhas Daftuar]

[-- Attachment #1: Type: text/plain, Size: 15064 bytes --]

(Apologies for the double-post -- I'm resending this message to the list
with much of the quoted text trimmed, because my first message was placed
in the moderation queue for being too large)

Hi,

Thanks for sharing your thoughts on packaged transaction relay.

The sole objective, as expressed in the OP proposal, is to:

"Propagate transactions that are incentive-compatible to mine, even if they
> don't meet minimum feerate alone."


I actually do think there are additional goals we should include in any
protocol change involving transaction relay, such as ensuring that we
minimize bandwidth waste as much as possible (as I mentioned in a previous
message in this thread).

While I understand your proposal seeks to improve on an idea of static
packages in favor of dynamic package construction based on knowledge a node
should have of its peers, I think the main drawback of your proposal is
that it doesn't take into account the complexities of what a peer's
"minimum feerate" might mean.  The consequence of this is that it's not
generally possible for a node to accurately guess whether a given
transaction should be sent in a package to a given peer, or not, and so in
addition to any "packaged transaction relay" mechanism that is implemented
by a transaction announcer, we'd still need to add protocol support for a
receiving peer to retrieve a package as well.

First of all, a node's feerate is a dynamic value.  BIP 133 allows for
nodes to send feefilter messages at any time during the lifetime of a peer
connection.  If we were to compare the feerate of ancestors of a relayed
transaction to the feerate in place at a peer as indicated by feefilter
messages, and use that determine whether those ancestors would have been
successfully relayed or not, then doing so accurately would seem to require
caching relay success for each transaction, for each peer, at the time such
transaction is relayed (or perhaps caching feefilter values that are
received from a peer?).  This seems likely to be undesirable, and, at any
rate, is more complex than merely comparing a pair of feerates.

But even more fundamental than feerates being dynamic is that feerate
itself is not a well-defined concept when applied to arbitrary transaction
(sub-)graphs, and this is at the crux of the difficulty in coming up with
proposals that would meet the objective of ensuring that transactions which
are incentive-compatible to mine all get relayed successfully across the
network.  Here are a couple examples that illustrate this:

- Let A be a low feerate transaction (below any peer's minimum feerate).
Let B and C be descendants of A (but are otherwise unrelated).  Suppose
these transactions are relayed to a node in the order A, B, C.  In the
algorithm you proposed, I believe the determination for whether C should be
announced to a given peer as a package (A, C) or as a singleton would
either (1) depend on whether the package (A, B) was sufficient to meet the
peer's feerate, or (2) waste bandwidth by engaging in packaged relay
whenever A was already successfully relayed as part of a package.  Both of
these approaches seem undesirable.

- Let A be a high fee, but low feerate transaction.  Suppose B is a
transaction that conflicts with A, has a high feerate, but lower total
fee.  In this situation, two different nodes that learned of these two
transactions in opposite order [(A, B) vs (B, A)] might be expected to have
differing mempools -- this at least would be the case in the BIP 125
algorithm (which requires that both feerate and total fee must increase
when replacing an existing transaction), and at any rate it's not obvious
from the information given which would be more optimal to include in a
block, as that depends on factors that go beyond just these two
transactions.  Suppose further that a new transaction C is relayed on the
network, which is a child of B and very high feerate, such that B + C have
higher fee and higher feerate than A, when taken together.  In this case
we'd want our relay protocol to ensure that even nodes which saw A first
should still have a chance to consider transaction C, but the packaging
design you propose (which would compare transaction B's feerate to the
peer's, and conclude packaging is unnecessary because B's feerate might
already exceed the peer's feerate) would not facilitate this.

To summarize, the point I'd make from these examples is that we should not
expect that "feerate" (whatever that means) alone will be a sufficient
predictor of what is in our peer's mempools.  So while there may be some
situations where a transaction relayer might be able to usefully package up
a transaction with its dependencies (perhaps in narrowly defined
situations), there will also always be situations where this isn't
possible, and what I conclude from that is that it should be helpful to add
to the protocol some way for the recipient of a transaction to request the
dependencies directly.

Taken together, I roughly understand Gloria's efforts here to be a
combination of these two approaches: add some amount of packaged
transaction relay for simple cases (ie where the transaction graph has been
sufficiently narrowed, to minimize bandwidth waste while reducing latency),
and also allow for a fallback mechanism where the recipient of a
transaction can efficiently retrieve dependencies.  There seems to be a
tradeoff involving latency, bandwidth, and robustness of these two
approaches (and maybe also implementation complexity), so I think it's
natural to expect that it will take some discussion and understanding of
what practices are common on the network and what behaviors wallet or other
software might adopt, given potential protocol changes, to figure out how
best to balance these ideas.

On Wed, Jun 8, 2022 at 6:43 PM <eric@voskuil.org> wrote:

> Hi Suhas/Gloria,
>
> Good questions. I've started a new thread because it became something
> else...
>
> Various ideas about packaging seem to be focused on the idea of an atomic
> message that is gossiped around the network like a transaction or block.
> From my perspective that seems to create a set of problems without good
> solutions, and it is not a proper analogy to those atomic structures. It
> may be worth taking the time to step back and take a close look at the
> underlying objective.
>
> The sole objective, as expressed in the OP proposal, is to:
>
> "Propagate transactions that are incentive-compatible to mine, even if
> they don't meet minimum feerate alone."
>
> Effectively producing this outcome with an atomic packaging approach while
> at the same time maintaining network invariants seems unlikely, if not
> impossible.
>
> Fees:
>
> A node knows what fee rate a peer will accept, and announces individual
> txs that satisfy peer.feerate. Similarly a node knows its own feerate, and
> SHOULD drop any peer that announces txs that do not satisfy node.feerate.
>
> Orphans:
>
> A node MAY drop a peer that announces txs that the node sees as orphans
> against its DAG. It SHOULD drop the orphan tx and MAY request missing
> ancestors. Presumably after some amount of time connected to peer, node
> does not expect to see any more orphans from that peer, so these choices
> could evolve with the channel. However, the design that can only consider
> each tx in isolation will continue to cause orphan announcements on the
> channel. A below peer.feerate tx does not get announced to peer, and later
> a descendant high peer.feerate does get announced to the peer - as an
> orphan.
>
> BIP133 (feefilter):
>
> "There could be a small number of edge cases where a node's mempool min
> fee is actually less than the filter value a peer is aware of and
> transactions with fee rates between these values will now be newly
> inhibited."
>
> https://github.com/bitcoin/bips/blob/master/bip-0133.mediawiki
>
> Whether the problem is "small" or not depends on the disparity between
> node fee rates, which is not a matter of protocol. This is an existing
> problem that can and should be dealt with in packaging, as part of the
> above objective.
>
> Packaged Transaction Relay:
>
> One might instead think of packaging as a per-connection function,
> operating over its transaction (input->output) DAG and the feerate of its
> own node and that of the peer. Logically a "package" is nothing more than a
> set of transactions (optimized by announcement). Only a node can
> effectively determine the packaging required by each of its peers, since
> only the node is aware of peer.feerate.
>
> The only way to avoid dead-ending packages (including individual
> transactions, as is the objective) is for a node to package txs for each
> peer. The origination of any package is then just a wallet peer doing what
> a node does - packaging transactions that satisfy peer.feerate (i.e. that
> of its node).
>
> Current transaction relay (txB->txA):
> ===============================
> Node0
> txA.feerate > node.feerate, and not orphaned (accept txA)
> txA.feerate > peer1.feerate (announce txA to peer1)
> txA.feerate < peer2.feerate (do not announce txA to peer2)
> -----
> txB.feerate > node.feerate (accept txB)
> txB.feerate > peer1.feerate (announce txB to peer1)
> txB.feerate > peer2.feerate (announce txB to peer2)
>
> Node1
> Sees/accepts txA and txB.
>
> Node2
> Never sees txA, sees/rejects txB (as an orphan).
>
> Packaged transaction relay (txB->txA):
> ===============================
> Node0
> txA.feerate > node.feerate, and not orphaned (accept txA)
> txA.feerate > peer1.feerate (announce txA to peer1)
> txA.feerate < peer2.feerate (do not announce txA to peer2)
> -----
> txB.feerate > node1.feerate (accept txB)
> txB.feerate > peer1.feerate (announce txB to peer1)
> txB.feerate > peer2.feerate (do not announce txB to peer2) <== avoid
> predictable orphan
> txA.feerate + txB.feerate > peer2.feerate (announce pkg(A, B) to peer2) <=
> create minimal package
>
> Node1
> Sees/accepts txA and txB.
>
> Node2
> pkg(A, B) > node2.feerate (accept txA, txB)
> txA.feerate > peer3.feerate (announce txA to peer3)
> txB.feerate > peer3.feerate (announce txB to peer3)
>
> Sees/accepts pkg(A, B).
>
> Node3
> Sees/accepts txA and txB. <= avoided unnecessary packaging
>
> Summary:
>
> In this design, any node that receives an announcement for a pkg (or tx)
> later determined to be less than node.feerate SHOULD drop the announcing
> peer. Unlike with existing tx relay, a node can become "current" and
> subsequently see few if any tx or pkg orphans, and MAY at some point decide
> to drop any peer that announces one. Notice that packages are created
> dynamically, and any package that doesn't need to be grouped gets trimmed
> down to individual transactions. Furthermore any tx that is "stuck" can be
> freed by simply sending another tx. The nodes at which the tx has become
> stuck will just package it up and relay it to peers. In other words, there
> is no impact on wallet implementation apart from raising the aggregate fee
> using a descendant transaction.
>
> This is barely a protocol change - it's primarily implementation. All that
> should be required is an additional INV element type, such as
> MSG_TX_PACKAGE.
>
> Additional constraints:
>
> * All elements of MSG_TX_PACKAGE in one INV message MUST to be of the same
> package.
> * A package MUST must define a set that can be mined into one block
> (size/sigops constraint).
> * A package SHOULD not contain confirmed txs (a race may cause this).
> * A package MUST minimally satisfy peer.feerate.
> * A partial tx order, as in the manner of the block.txs ordering, MUST be
> imposed.
> * A node SHOULD drop a peer that sends a package (or tx) below
> node.feerate.
> * A node MAY drop a peer that sends a non-minimal package according to
> node.feerate.
>
> The partial ordering of block.txs introduces an ordering constraint that
> precludes full parallelism in validating input attachment. This is an
> implementation artifact that made its way into consensus. However in the
> case of packaging, the set of txs is not presumed to be valid under the
> proof of work DoS guard. As such constraints should minimize the
> work/traffic required to invalidate the message. The partial order
> constraint ensures that the DAG can be built incrementally, dropping the
> attempt (and peer as desired) as soon as the first orphan is discovered. As
> a result the network traffic and work required is not materially different
> than with tx relay, with two exceptions.
>
> These are the two central aspects of this approach (Avoiding Predictable
> Orphans and Creating Minimal Packages). These are graph search algorithms,
> some basic computer science. Minimality requires only that the package does
> not introduce txs that are not necessary to reach the peer.feerate (as
> these can always be packaged separately). It does not require that nodes
> all generate the same packages. It does not require negotiation, package
> identity, cryptography, or hashing. As a graph search it should be O(n)
> where n is the unconfirmed ancestry of the package, but should typically be
> much lower, if not a single step.
>
> Sufficiently-low-fee nodes will see only single txs. Moderate-fee nodes
> may cause partial breakup of packages. Sufficiently high fee nodes will
> cause peers (having received and completed the acceptance of a tx/pkg with
> pkg.feerate < peer.feerate) to navigate from each tx/package external input
> until reaching txs above peer.feerate, or confirmed (both of which the peer
> is presumed to already have). If the pkg.feerate is sufficiently high to
> connect all external inputs to the intervening txs, they are added to the
> package and it is announced to the high fee peer. Note that the individual
> tx.feerate > peer.feerate is insufficient to ensure that the peer should
> have the tx, as there may be ancestor txs that do not, and for which the tx
> was insufficient to cause them to be packaged. So a non-caching algorithm
> must be able to chase each package external input to a confirmed tx (or
> cache the unconfirmed ancestry fee rate at each tx). Note that fee rates
> are not directly additive, both size/weight and fee are required for
> summation (and aggregate sigops should be considered).
>
> This makes no assumptions about current implementations. The design would
> call for maintenance of a transaction (input->output) DAG with tx.feerate
> on each tx. This could be the unconfirmed tx graph (i.e. "memory pool")
> though it does not require maintenance of anything more than the parameters
> necessary to confirm a set of validated txs within a block. It is very
> reasonable to require this of any participating node. A simple version
> negotiation can identify a package-accepting/sending nodes.
>
> I have thought about this for some time, but have not implemented either
> the graph search, source code, or BIP. Just wrote this off the top of my
> head. So I am sure there are some things I have incorrect or failed to
> consider. But I think it's worth discussing it at this point.
>
> e
>
>
>

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Re: [bitcoin-dev] Packaged Transaction Relay

[alicexbt]

Hi Eric,


> If by "range" you mean a connected tx subgraph, I don't see why not. But note that nodes only operate over signed txs. PSBT is a wallet workflow.

Matt Corallo mentioned that pre-signed transactions created with low fee rate become an issue when they are broadcasted after a long time and there is a high demand for block space at that moment.

Example: 

Bob created PSBT1 in a multi party contract with fee rate 5 sat/vbyte however its taking hours/days to confirm the transaction with such low fee rate.

Carol created PSBT1 (5 sat/vbyte), PSBT2 (10 sat/vbyte) and PSBT3 (20 sat/vbyte) for spending same inputs. She broadcasted PSBT3 which got confirmed in a few minutes. 


> Always. Only signed transactions are accepted. But assuming you are referring to a transaction that has been produced by a pre-signing workflow, I'm not sure how this would be distinct from any other tx.


`minfeefilter` for all peers of my node was 0.00001000 at the time of writing this email. I am assuming nobody creates pre-signed transaction with fee rate below 1 sat/vbyte. How often does it happen that `minfeefilter` is above this default value?


> I'm not sure I follow this, maybe you could reword it. But it seems that you are saying that CPFP fee-bumping is a problem scenario and the complexity of the proposed solutions are not justified by such scenarios.


Sorry that sentence was confusing. Yes complexity isn't justified for CPFP fee-bumping txs below minimum fee rate.


> There are many node implementations used presently. And of course these are protocol proposals, which presumes more than one implementation.


Yes, a few implementations exist (knots, libbitcoin, btcd, bcoin etc.) however they aren't used by lot of nodes. Based on this [chart][1] 98% nodes use bitcoin core. Lot of bitcoin protocol proposals are influenced by bitcoin core contributors and things could be different if even 30% nodes used other implementations.


> I don't consider this relevant to any protocol considerations. Miners should always be expected to select the most optimal set of txs available in the time available to do so.


Agree, miners should be expected to select most optimal set of txs. However, according to one [comment][2] by Pieter Wuille, miners could affect the security of some bitcoin projects with MEV.


> Over time we are likely to see that the only policies that remain in widespread application are those that are necessary for DOS protection (fee rate), as other restrictions are not economically rational and cannot be enforced. We've seen recent debate regarding dust policy, and op_return policy. "non-standard" txs are perfectly valid but get stuck very easily. I'll reiterate, any policy beyond what is published via the protocol will cause the above problems.

I completely agree with this.


[1]: https://luke.dashjr.org/programs/bitcoin/files/charts/software.html
[2]: https://bitcoin.stackexchange.com/questions/107787/front-running-in-bitcoin#comment123441_107796


/dev/fd0

Sent with Proton Mail secure email.

------- Original Message -------
On Tuesday, September 27th, 2022 at 2:49 AM, <eric@voskuil.org> wrote:


> > Hi Eric,
> > 
> > This email wasn't answered by anyone on mailing list however I did some
> > research about packages yesterday including this email and below are my
> > observations, questions etc.
> 
> 
> Hello, thanks for the reply.
> 
> > > The sole objective, as expressed in the OP proposal, is to:
> > > 
> > > "Propagate transactions that are incentive-compatible to mine, even if they
> > > don't meet minimum feerate alone."
> > 
> > According to bitcoinops: Without package relay, it’s not possible to
> > effectively CPFP fee bump a transaction that’s below the minimum feerate
> > nodes accept.
> 
> 
> Yes, the problem statement is not in question, just the mechanism of resolution. The problem of stuck txs arises from minimum fee rate policy, which is a necessary DOS guard.
> 
> A secondary issue is that of orphan relay. As a node must allow receipt of orphans, it has no means to differentiate a flood of unconfirmable txs from those that are confirmable.
> 
> > Matt Corallo's thoughts in a bitcoin core issue:
> > 
> > "Matt Corallo recently wrote about an example on the bitcoin-dev mailing list
> > involving lightning transactions, where pre-signed transactions might be
> > broadcast to the blockchain long after they were generated, and thus not
> > have been created with a fee that is sufficient to be confirmed quickly (or
> > even be accepted to node mempools). In such situations, channel
> > participants may need to use chained transactions (CPFP) in order to increase
> > the confirmation speed of such transactions, and that implies we may need
> > to introduce a mechanism for those parent transactions to be relayed along
> > with their higher feerate children, even if the parent transaction would be
> > rejected by itself."
> 
> 
> While this is a valid scenario, the problems directly affect Bitcoin. Those problems propagate to layers, but are not unique to layering.
> 
> > 1)Is it possible to have multiple pre-signed transactions with different fee
> > rates in a range? Example: PSBT1: 5 sat/vbyte, PSBT2: 10 sat/vbyte, PSBT3: 20
> > sat/vbyte and PSBT4: 100 sat/vbyte
> 
> 
> If by "range" you mean a connected tx subgraph, I don't see why not. But note that nodes only operate over signed txs. PSBT is a wallet workflow.
> 
> > 2)How would covenants affect this problem?
> 
> 
> There are a good number of covenant proposals, though I assume they are all implemented within script. If a tx is confirmable and satisfies fee rate (for DOS protection), it is relayable. Covenants affect confirmability and should not have any unique impact on relay.
> 
> > 3)How often does it happen that a pre-signed tx gets rejected by nodes
> > because it did not meet the minimum fee rate? Is it predictable and could be
> > managed in a different way?
> 
> 
> Always. Only signed transactions are accepted. But assuming you are referring to a transaction that has been produced by a pre-signing workflow, I'm not sure how this would be distinct from any other tx.
> 
> > After reading several links related to packages and bitcoin core pull requests,
> > I found it anti-bitcoin to introduce so much complexity because its not
> > possible to CPFP fee bump a tx below minimum fee rate.
> 
> 
> I'm not sure I follow this, maybe you could reword it. But it seems that you are saying that CPFP fee-bumping is a problem scenario and the complexity of the proposed solutions are not justified by such scenarios.
> 
> I would say that the problem is real, and that the least complex option is generally preferred. There are always tradeoffs, and balancing these is part of protocol development. But as a rule, complexity within a protocol (communication) is to be avoided where possible.
> 
> > > Furthermore any tx that is "stuck" can be freed by simply sending another
> > > tx. The nodes at which the tx has become stuck will just package it up and
> > > relay it to peers. In other words, there is no impact on wallet implementation
> > > apart from raising the aggregate fee using a descendant transaction.
> > 
> > It is easy to send another tx if there is only one user involved however
> > packages are trying to fix issues in which multiple users and transaction pre-
> > signed between them are involved. So, it will be difficult to coordinate and
> > create new pre-signed transactions in some cases although it is possible for
> > some use cases.
> 
> 
> Given that nodes do not deal in presigned txs, this coordination difficulty could not be increased in any scenario.
> 
> A node produces sets of txs ("packages") dynamically to satisfy its peer's feerate. When a wallet broadcasts a tx/package to a node, it is operating as a peer on the p2p network. The wallet simply implements the same dynamic packaging algorithm as any peer - because it is a peer.
> 
> > > This is barely a protocol change - it's primarily implementation. All that
> > > should be required is an additional INV element type, such as
> > > MSG_TX_PACKAGE.
> > 
> > > * All elements of MSG_TX_PACKAGE in one INV message MUST to be of
> > > the same package.
> > > * A package MUST must define a set that can be mined into one block
> > > (size/sigops constraint).
> > > * A package SHOULD not contain confirmed txs (a race may cause this).
> > > * A package MUST minimally satisfy peer.feerate.
> > > * A partial tx order, as in the manner of the block.txs ordering, MUST be
> > > imposed.
> > > * A node SHOULD drop a peer that sends a package (or tx) below
> > > node.feerate.
> > > * A node MAY drop a peer that sends a non-minimal package according to
> > > node.feerate.
> > 
> > This makes sense particularly if multiple node implementations are used in
> > future.
> 
> 
> There are many node implementations used presently. And of course these are protocol proposals, which presumes more than one implementation.
> 
> > My other questions:
> > 
> > a)If a package has tx1, tx2, tx3, tx4 and tx5 and miner just include tx1 and tx2
> > in the block, how does this affect the projects considered for packages
> > proposal?
> 
> 
> I will leave that to authors of such proposals to answer. However in what I have proposed it just means tx3/4/5 get considered for subsequent block inclusion to the extent that fee rate policy is satisfied.
> 
> One of the several problems with static construction of packages is that they can still get stuck by fee rate policy. This is just kicking the can down the road while complicating the protocol.
> 
> > b)How does changing the order of txs in a package affect these transactions?
> 
> 
> There is no impact. I proposed the partial ordering to facilitate fail fast.
> 
> The partial ordering in block txs is unnecessary (given the PoW DOS guard). This is a consequence of the order imposed by Satoshi's implementation and only serves to slow validation (order constrains concurrency).
> 
> > c)Do packages introduce more attack vectors in bitcoin for front running or
> > MEV? MEV in bitcoin currently only affects the projects that are considered
> > in packages proposal.
> 
> 
> I don't consider this relevant to any protocol considerations. Miners should always be expected to select the most optimal set of txs available in the time available to do so.
> 
> > d)What if the package contains a transactions with sanctioned address?
> 
> 
> One can consider this a policy, much like fee rate. Any policy that is applied to transactions and not known to its peers will result in the node receiving orphans. As such the node either must allow orphans or drop peers sending orphans under the assumption that the peer is expected to have implemented the same policy.
> 
> > e)Why would miners use packages if the existing scenario in terms of fees
> > per block is beneficial for them?
> 
> 
> The presumption is that the miner is only ever seeing txs that satisfy its fee rate policy, so this is just more opportunity.
> 
> I'd add that the problem of "pinning" is related, but exacerbated by opaque policy (internal to certain implementations). Any node that ejects txs from its pool of valid but unconfirmed txs that satisfy fee rate policy is going to see orphans and going to cause txs to get stuck. This is one of the many problems with placing an arbitrary bound on the size of this pool.
> 
> A subset of this problem is RBF policy. It is nice to see some movement toward generalizing RBF. The term is really a misnomer. Conflicting txs and subgraphs of txs are only problematic in the case of DOS, which is also resolved through advertised fee policy. Any node that imposes policy beyond this will also see orphans and cause txs to get stuck.
> 
> The scenario and therefore complexity consequences of an implementation-specific memory-constrained tx pool are becoming increasingly apparent. These are implementation issues, not protocol issues. This can be observed in a recent thread: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2022-September/020937.html
> 
> Over time we are likely to see that the only policies that remain in widespread application are those that are necessary for DOS protection (fee rate), as other restrictions are not economically rational and cannot be enforced. We've seen recent debate regarding dust policy, and op_return policy. "non-standard" txs are perfectly valid but get stuck very easily. I'll reiterate, any policy beyond what is published via the protocol will cause the above problems.
> 
> e
> 
> > /dev/fd0
> > 
> > Sent with Proton Mail secure email.
> > 
> > ------- Original Message -------
> > On Thursday, June 9th, 2022 at 4:13 AM, Eric Voskuil via bitcoin-dev <bitcoin-
> > dev@lists.linuxfoundation.org> wrote:
> > 
> > > Hi Suhas/Gloria,
> > > 
> > > Good questions. I've started a new thread because it became something
> > > else...
> > > 
> > > Various ideas about packaging seem to be focused on the idea of an atomic
> > > message that is gossiped around the network like a transaction or block.
> > > From my perspective that seems to create a set of problems without good
> > > solutions, and it is not a proper analogy to those atomic structures. It may be
> > > worth taking the time to step back and take a close look at the underlying
> > > objective.
> > > 
> > > The sole objective, as expressed in the OP proposal, is to:
> > > 
> > > "Propagate transactions that are incentive-compatible to mine, even if they
> > > don't meet minimum feerate alone."
> > > 
> > > Effectively producing this outcome with an atomic packaging approach
> > > while at the same time maintaining network invariants seems unlikely, if not
> > > impossible.
> > > 
> > > Fees:
> > > 
> > > A node knows what fee rate a peer will accept, and announces individual
> > > txs that satisfy peer.feerate. Similarly a node knows its own feerate, and
> > > SHOULD drop any peer that announces txs that do not satisfy node.feerate.
> > > 
> > > Orphans:
> > > 
> > > A node MAY drop a peer that announces txs that the node sees as orphans
> > > against its DAG. It SHOULD drop the orphan tx and MAY request missing
> > > ancestors. Presumably after some amount of time connected to peer, node
> > > does not expect to see any more orphans from that peer, so these choices
> > > could evolve with the channel. However, the design that can only consider
> > > each tx in isolation will continue to cause orphan announcements on the
> > > channel. A below peer.feerate tx does not get announced to peer, and later
> > > a descendant high peer.feerate does get announced to the peer - as an
> > > orphan.
> > > 
> > > BIP133 (feefilter):
> > > 
> > > "There could be a small number of edge cases where a node's mempool
> > > min fee is actually less than the filter value a peer is aware of and
> > > transactions with fee rates between these values will now be newly
> > > inhibited."
> > > 
> > > https://github.com/bitcoin/bips/blob/master/bip-0133.mediawiki
> > > 
> > > Whether the problem is "small" or not depends on the disparity between
> > > node fee rates, which is not a matter of protocol. This is an existing problem
> > > that can and should be dealt with in packaging, as part of the above
> > > objective.
> > > 
> > > Packaged Transaction Relay:
> > > 
> > > One might instead think of packaging as a per-connection function,
> > > operating over its transaction (input->output) DAG and the feerate of its
> > > own node and that of the peer. Logically a "package" is nothing more than a
> > > set of transactions (optimized by announcement). Only a node can
> > > effectively determine the packaging required by each of its peers, since only
> > > the node is aware of peer.feerate.
> > > 
> > > The only way to avoid dead-ending packages (including individual
> > > transactions, as is the objective) is for a node to package txs for each peer.
> > > The origination of any package is then just a wallet peer doing what a node
> > > does - packaging transactions that satisfy peer.feerate (i.e. that of its node).
> > > 
> > > Current transaction relay (txB->txA):
> > > 
> > > ===============================
> > > Node0
> > > txA.feerate > node.feerate, and not orphaned (accept txA)
> > > 
> > > txA.feerate > peer1.feerate (announce txA to peer1)
> > > 
> > > txA.feerate < peer2.feerate (do not announce txA to peer2)
> > > -----
> > > txB.feerate > node.feerate (accept txB)
> > > 
> > > txB.feerate > peer1.feerate (announce txB to peer1)
> > > 
> > > txB.feerate > peer2.feerate (announce txB to peer2)
> > > 
> > > Node1
> > > Sees/accepts txA and txB.
> > > 
> > > Node2
> > > Never sees txA, sees/rejects txB (as an orphan).
> > > 
> > > Packaged transaction relay (txB->txA):
> > > 
> > > ===============================
> > > Node0
> > > txA.feerate > node.feerate, and not orphaned (accept txA)
> > > 
> > > txA.feerate > peer1.feerate (announce txA to peer1)
> > > 
> > > txA.feerate < peer2.feerate (do not announce txA to peer2)
> > > -----
> > > txB.feerate > node1.feerate (accept txB)
> > > 
> > > txB.feerate > peer1.feerate (announce txB to peer1)
> > > 
> > > txB.feerate > peer2.feerate (do not announce txB to peer2) <== avoid
> > > predictable orphan
> > > 
> > > txA.feerate + txB.feerate > peer2.feerate (announce pkg(A, B) to
> > > peer2) <= create minimal package
> > > 
> > > Node1
> > > Sees/accepts txA and txB.
> > > 
> > > Node2
> > > pkg(A, B) > node2.feerate (accept txA, txB)
> > > 
> > > txA.feerate > peer3.feerate (announce txA to peer3)
> > > 
> > > txB.feerate > peer3.feerate (announce txB to peer3)
> > > 
> > > Sees/accepts pkg(A, B).
> > > 
> > > Node3
> > > Sees/accepts txA and txB. <= avoided unnecessary packaging
> > > 
> > > Summary:
> > > 
> > > In this design, any node that receives an announcement for a pkg (or tx)
> > > later determined to be less than node.feerate SHOULD drop the announcing
> > > peer. Unlike with existing tx relay, a node can become "current" and
> > > subsequently see few if any tx or pkg orphans, and MAY at some point
> > > decide to drop any peer that announces one. Notice that packages are
> > > created dynamically, and any package that doesn't need to be grouped gets
> > > trimmed down to individual transactions. Furthermore any tx that is "stuck"
> > > can be freed by simply sending another tx. The nodes at which the tx has
> > > become stuck will just package it up and relay it to peers. In other words,
> > > there is no impact on wallet implementation apart from raising the aggregate
> > > fee using a descendant transaction.
> > > 
> > > This is barely a protocol change - it's primarily implementation. All that
> > > should be required is an additional INV element type, such as
> > > MSG_TX_PACKAGE.
> > > 
> > > Additional constraints:
> > > 
> > > * All elements of MSG_TX_PACKAGE in one INV message MUST to be of
> > > the same package.
> > > * A package MUST must define a set that can be mined into one block
> > > (size/sigops constraint).
> > > * A package SHOULD not contain confirmed txs (a race may cause this).
> > > * A package MUST minimally satisfy peer.feerate.
> > > * A partial tx order, as in the manner of the block.txs ordering, MUST be
> > > imposed.
> > > * A node SHOULD drop a peer that sends a package (or tx) below
> > > node.feerate.
> > > * A node MAY drop a peer that sends a non-minimal package according to
> > > node.feerate.
> > > 
> > > The partial ordering of block.txs introduces an ordering constraint that
> > > precludes full parallelism in validating input attachment. This is an
> > > implementation artifact that made its way into consensus. However in the
> > > case of packaging, the set of txs is not presumed to be valid under the proof
> > > of work DoS guard. As such constraints should minimize the work/traffic
> > > required to invalidate the message. The partial order constraint ensures that
> > > the DAG can be built incrementally, dropping the attempt (and peer as
> > > desired) as soon as the first orphan is discovered. As a result the network
> > > traffic and work required is not materially different than with tx relay, with
> > > two exceptions.
> > > 
> > > These are the two central aspects of this approach (Avoiding Predictable
> > > Orphans and Creating Minimal Packages). These are graph search algorithms,
> > > some basic computer science. Minimality requires only that the package does
> > > not introduce txs that are not necessary to reach the peer.feerate (as these
> > > can always be packaged separately). It does not require that nodes all
> > > generate the same packages. It does not require negotiation, package
> > > identity, cryptography, or hashing. As a graph search it should be O(n) where
> > > n is the unconfirmed ancestry of the package, but should typically be much
> > > lower, if not a single step.
> > > 
> > > Sufficiently-low-fee nodes will see only single txs. Moderate-fee
> > > nodes may cause partial breakup of packages. Sufficiently high fee
> > > nodes will cause peers (having received and completed the acceptance
> > > of a tx/pkg with pkg.feerate < peer.feerate) to navigate from each
> > > tx/package external input until reaching txs above peer.feerate, or
> > > confirmed (both of which the peer is presumed to already have). If the
> > > pkg.feerate is sufficiently high to connect all external inputs to the
> > > intervening txs, they are added to the package and it is announced to
> > > the high fee peer. Note that the individual tx.feerate > peer.feerate
> > > is insufficient to ensure that the peer should have the tx, as there
> > > may be ancestor txs that do not, and for which the tx was insufficient
> > > to cause them to be packaged. So a non-caching algorithm must be able
> > > to chase each package external input to a confirmed tx (or cache the
> > > unconfirmed ancestry fee rate at each tx). Note that fee rates are not
> > > directly additive, both size/
> > > 
> > > weight and fee are required for summation (and aggregate sigops should
> > > be considered).
> > > 
> > > This makes no assumptions about current implementations. The design
> > > would call for maintenance of a transaction (input->output) DAG with
> > > tx.feerate on each tx. This could be the unconfirmed tx graph (i.e. "memory
> > > pool") though it does not require maintenance of anything more than the
> > > parameters necessary to confirm a set of validated txs within a block. It is
> > > very reasonable to require this of any participating node. A simple version
> > > negotiation can identify a package-accepting/sending nodes.
> > > 
> > > I have thought about this for some time, but have not implemented either
> > > the graph search, source code, or BIP. Just wrote this off the top of my head.
> > > So I am sure there are some things I have incorrect or failed to consider. But I
> > > think it's worth discussing it at this point.
> > > 
> > > e
> > > 
> > > > -----Original Message-----
> > > > From: bitcoin-dev bitcoin-dev-bounces@lists.linuxfoundation.org On
> > > > Behalf Of Suhas Daftuar via bitcoin-dev
> > > > Sent: Wednesday, June 8, 2022 8:59 AM
> > > > To: Bitcoin Protocol Discussion
> > > > bitcoin-dev@lists.linuxfoundation.org
> > > > Subject: Re: [bitcoin-dev] Package Relay Proposal
> > > > 
> > > > Hi,
> > > > 
> > > > Thanks again for your work on this!
> > > > 
> > > > One question I have is about potential bandwidth waste in the case
> > > > of nodes running with different policy rules. Here's my
> > > > understanding of a scenario I think could happen:
> > > > 
> > > > 1) Transaction A is both low-fee and non-standard to some nodes on
> > > > the network.
> > > > 2) Whenever a transaction T that spends A is relayed, new nodes will
> > > > send INV(PKGINFO1, T) to all package-relay peers.
> > > > 3) Nodes on the network that have implemented package relay, but do
> > > > not accept A, will send getdata(PKGINFO1, T) and learn all of T's
> > > > unconfirmed parents (~32 bytes * number of parents(T)).
> > > > 4) Such nodes will reject T. But because of transaction
> > > > malleability, and to avoid being blinded to a transaction
> > > > unnecessarily, these nodes will likely still send getdata(PKGINFO1,
> > > > T) to every node that announces T, in case someone has a transaction
> > > > that includes an alternate set of parent transactions that would pass
> > > > policy checks.
> > > > 
> > > > Is that understanding correct? I think a good design goal would be
> > > > to not waste bandwidth in non-adversarial situations. In this case,
> > > > there would be bandwidth waste from downloading duplicate data from
> > > > all your peers, just because the announcement doesn't commit to the
> > > > set of parent wtxids that we'd get from the peer (and so we are
> > > > unable to determine that all our peers would be telling us the same thing,
> > > > just based on the announcement).
> > > > 
> > > > Some ways to mitigate this might be to: (a) include a hash (maybe
> > > > even just a 20-byte hash -- is that enough security?) of the package
> > > > wtxids (in some canonical ordering) along with the wtxid of the
> > > > child in the initial announcement; (b) limit the use of v1 packages
> > > > to transactions with very few parents (I don't know if this is reasonable
> > > > for the use cases we have in mind).
> > > > 
> > > > Another point I wanted to bring up is about the rules around v1
> > > > package validation generally, and the use of a blockhash in
> > > > transaction relay specifically. My first observation is that it
> > > > won't always be the case that a v1 package relay node will be able
> > > > to validate that a set of package transactions is fully sorted
> > > > topologically, because there may be (non-parent) ancestors that are
> > > > missing from the package and the best a peer can validate is
> > > > topology within the package -- this means that a peer can validly
> > > > (under this
> > > > BIP) relay transaction packages out of the true topological sort (if
> > > > all ancestors were included).
> > > > 
> > > > This makes me wonder how useful this topological rule is. I suppose
> > > > there is some value in preventing completely broken implementations
> > > > from staying connected and so there is no harm in having the rule,
> > > > but perhaps it would be helpful to add that nodes SHOULD order
> > > > transactions based on topological sort in the complete transaction
> > > > graph, so that if missing-from-package ancestors are already known
> > > > by a peer (which is the expected case when using v1 package relay on
> > > > transactions that have more than one generation of unconfirmed
> > > > ancestor) then the remaining transactions are already properly ordered,
> > > > and this is helpful even if unenforceable in general.
> > > > 
> > > > The other observation I wanted to make was that having transaction
> > > > relay gated on whether two nodes agree on chain tip seems like an
> > > > overly restrictive criteria. I think an important design principle
> > > > is that we want to minimize disruption from network splits -- if
> > > > there are competing blocks found in a small window of time, it's
> > > > likely that the utxo set is not materially different on the two
> > > > chains (assuming miners are selecting from roughly the same sets of
> > > > transactions when this happens, which is typical). Having
> > > > transaction relay bifurcate on the two network halves would seem to
> > > > exacerbate the difference between the two sides of the split --
> > > > users ought to be agnostic about how benign splits are resolved and
> > > > would likely want their transactions to relay across the whole network.
> > > > 
> > > > Additionally, use of a chain tip might impose a larger burden than
> > > > is necessary on software that would seek to participate in
> > > > transaction relay without implementing headers sync/validation. I
> > > > don't know what software exists on the network, but I imagine there
> > > > are a lot of scripts out there for transaction submission to the
> > > > public p2p network, and in thinking about modifying such a script to
> > > > utilize package relay it seems like an unnecessary added burden to first
> > > > learn a node's tip before trying to relay a transaction.
> > > > 
> > > > Could you explain again what the benefit of including the blockhash
> > > > is? It seems like it is just so that a node could prioritize
> > > > transaction relay from peers with the same chain tip to maximize the
> > > > likelihood of transaction acceptance, but in the common case this
> > > > seems like a pretty negligible concern, and in the case of a chain
> > > > fork that persists for many minutes it seems better to me that we
> > > > not partition the network into package-relay regimes and just risk a
> > > > little extra bandwidth in one direction or the other. If we solve
> > > > the problem I brought up at the beginning (of de-duplicating package
> > > > data across peers with a package-wtxid-commitment in the
> > > > announcement), I think this is just some wasted pkginfo bandwidth on
> > > > a single-link, and not across links (as we could cache validation failure for a
> > > > package-hash to avoid re-requesting duplicate pkginfo1 messages).
> > > > 
> > > > Best,
> > > > Suhas
> > > > 
> > > > On Tue, Jun 7, 2022 at 1:57 PM Gloria Zhao via bitcoin-dev <bitcoin-
> > > > dev@lists.linuxfoundation.org <mailto:bitcoin-
> > > > dev@lists.linuxfoundation.org> > wrote:
> > > > 
> > > > Hi Eric, aj, all,
> > > > 
> > > > Sorry for the delayed response. @aj I'm including some paraphrased
> > > > points from our offline discussion (thanks).
> > > > 
> > > > > Other idea: what if you encode the parent txs as a short hash of
> > > > > the wtxid (something like bip152 short ids? perhaps seeded per
> > > > > peer so collisions will be different per peer?) and include that in the inv
> > > > > announcement?
> > > > > Would that work to avoid a round trip almost all of the time,
> > > > > while still giving you enough info to save bw by deduping parents?
> > > > 
> > > > > As I suggested earlier, a package is fundamentally a compact block
> > > > > (or
> > > > > block) announcement without the header. Compact block (BIP152)
> > > > > announcement is already well-defined and widely implemented...
> > > > 
> > > > > Let us not reinvent the wheel and/or introduce accidental
> > > > > complexity. I see no reason why packaging is not simply BIP152
> > > > > without the 'header'
> > > > > field, an
> > > > > updated protocol version, and the following sort of changes to
> > > > > names
> > > > 
> > > > Interestingly, "why not use BIP 152 shortids to save bandwidth?" is
> > > > by far the most common suggestion I hear (including offline feedback).
> > > > Here's a full explanation:
> > > > 
> > > > BIP 152 shortens transaction hashes (32 bytes) to shortids (6 bytes)
> > > > to save a significant amount of network bandwidth, which is
> > > > extremely important in block relay. However, this comes at the
> > > > expense of computational complexity. There is no way to directly
> > > > calculate a transaction hash from a shortid; upon receipt of a
> > > > compact block, a node is expected to calculate the shortids of every
> > > > unconfirmed transaction it knows about to find the matches (BIP 152:
> > > > 1, Bitcoin Core: 2). This is expensive but appropriate for block
> > > > relay, since the block must have a valid Proof of Work and new
> > > > blocks only come every ~10 minutes. On the other hand, if we require
> > > > nodes to calculate shortids for every transaction in their mempools every
> > > > time they receive a package, we are creating a DoS vector.
> > > > Unconfirmed transactions don't need PoW and, to have a live
> > > > transaction relay network, we should expect nodes to handle
> > > > transactions at a high-ish rate (i.e. at least 1000s of times more
> > > > transactions than blocks). We can't pre- calculate or cache shortids
> > > > for mempool transactions, since the SipHash key depends on the block
> > > > hash and a per-connection salt.
> > > > 
> > > > Additionally, shortid calculation is not designed to prevent
> > > > intentional individual collisions. If we were to use these shortids
> > > > to deduplicate transactions we've supposedly already seen, we may
> > > > have a censorship vector. Again, these tradeoffs make sense for
> > > > compact block relay (see shortid section in BIP 152 [3]), but not package
> > > > relay.
> > > > 
> > > > TLDR: DoSy if we calculate shortids on every package and censorship
> > > > vector if we use shortids for deduplication.
> > > > 
> > > > > Given this message there is no reason to send a (potentially
> > > > > bogus) fee rate with every package. It can only be validated by
> > > > > obtaining the full set of txs, and the only recourse is dropping
> > > > > (etc.) the peer, as is the case with single txs.
> > > > 
> > > > Yeah, I agree with this. Combined with the previous discussion with
> > > > aj (i.e. we can't accurately communicate the incentive compatibility
> > > > of a package without sending the full graph, and this whole dance is
> > > > to avoid downloading a few low-fee transactions in uncommon edge
> > > > cases), I've realized I should remove the fee + weight information
> > > > from pkginfo. Yay for less complexity!
> > > > 
> > > > Also, this might be pedantic, but I said something incorrect earlier
> > > > and would like to correct myself:
> > > > 
> > > > > > In theory, yes, but maybe it was announced earlier (while our
> > > > > > node was down?) or had dropped from our mempool or similar,
> > > > > > either way we don't have those txs yet.
> > > > 
> > > > I said "It's fine if they have Erlay, since a sender would know in
> > > > advance that B is missing and announce it as a package." But this
> > > > isn't true since we're only using reconciliation in place of
> > > > flooding to announce transactions as they arrive, not for
> > > > rebroadcast, and we're not doing full mempool set reconciliation. In
> > > > any case, making sure a node receives the transactions announced
> > > > when it was offline is not something we guarantee, not an intended use
> > > > case for package relay, and not worsened by this.
> > > > 
> > > > Thanks for your feedback!
> > > > 
> > > > Best,
> > > > 
> > > > Gloria
> > > > 
> > > > 0152.mediawiki#cmpctblock
> > > > 2:
> > > > https://github.com/bitcoin/bitcoin/blob/master/src/blockencodings.cp
> > > > p#L49
> > > > [3]: https://github.com/bitcoin/bips/blob/master/bip-
> > > > 0152.mediawiki#short-transaction-id-calculation
> > > > 
> > > > On Thu, May 26, 2022 at 3:59 AM <eric@voskuil.org
> > > > mailto:eric@voskuil.org > wrote:
> > > > 
> > > > Given that packages have no header, the package requires identity in
> > > > a
> > > > BIP152 scheme. For example 'header' and 'blockhash' fields can be
> > > > replaced with a Merkle root (e.g. "identity" field) for the package,
> > > > uniquely identifying the partially-ordered set of txs. And use of
> > > > 'getdata' (to obtain a package by hash) can be eliminated (not a use
> > > > case).
> > > > 
> > > > e
> > > > 
> > > > > -----Original Message-----
> > > > > From: eric@voskuil.org mailto:eric@voskuil.org
> > > > > <eric@voskuil.org mailto:eric@voskuil.org >
> > > > > Sent: Wednesday, May 25, 2022 1:52 PM
> > > > > To: 'Anthony Towns' <aj@erisian.com.au
> > > > > mailto:aj@erisian.com.au >; 'Bitcoin Protocol Discussion'
> > > > > <bitcoin-dev@lists.linuxfoundation.org <mailto:bitcoin-
> > > > > dev@lists.linuxfoundation.org> >; 'Gloria Zhao'
> > > > > <gloriajzhao@gmail.com mailto:gloriajzhao@gmail.com >
> > > > > Subject: RE: [bitcoin-dev] Package Relay Proposal
> > > > > 
> > > > > > From: bitcoin-dev <bitcoin-dev-
> > > > > > bounces@lists.linuxfoundation.org <mailto:bitcoin-dev-
> > > > > > bounces@lists.linuxfoundation.org> > On
> > > > > > Behalf
> > > > > > Of Anthony Towns via bitcoin-dev
> > > > > > Sent: Wednesday, May 25, 2022 11:56 AM
> > > > > 
> > > > > > So the other thing is what happens if the peer
> > > > > > announcing packages to us
> > > > > > is
> > > > > > dishonest?
> > > > > > 
> > > > > > They announce pkg X, say X has parents A B C and the fee
> > > > > > rate is
> > > > > > garbage.
> > > > > > But
> > > > > > actually X has parent D and the fee rate is excellent. Do
> > > > > > we request the
> > > > > > package from another peer, or every peer, to double
> > > > > > check? Otherwise
> > > > > > we're
> > > > > > allowing the first peer we ask about a package to censor
> > > > > > that tx from
> > > > > > us?
> > > > > > 
> > > > > > I think the fix for that is just to provide the fee and weight
> > > > > > when
> > > > > > announcing
> > > > > > the package rather than only being asked for its info?
> > > > > > Then if one peer
> > > > > > makes
> > > > > > it sound like a good deal you ask for the parent txids from
> > > > > > them,
> > > > > > dedupe,
> > > > > > request, and verify they were honest about the parents.
> > > > > 
> > > > > Single tx broadcasts do not carry an advertised fee rate,
> > > > > however the'
> > > > > feefilter' message (BIP133) provides this distinction. This
> > > > > should be
> > > > > interpreted as applicable to packages. Given this message
> > > > > there is no
> > > > > reason
> > > > > to send a (potentially bogus) fee rate with every package. It
> > > > > can only be
> > > > > validated by obtaining the full set of txs, and the only
> > > > > recourse is
> > > > > dropping (etc.) the peer, as is the case with single txs.
> > > > > Relying on the
> > > > > existing message is simpler, more consistent, and more
> > > > > efficient.
> > > > > 
> > > > > > > > Is it plausible to add the graph in?
> > > > > > 
> > > > > > Likewise, I think you'd have to have the graph info from
> > > > > > many nodes if
> > > > > > you're
> > > > > > going to make decisions based on it and don't want
> > > > > > hostile peers to be
> > > > > > able to
> > > > > > trick you into ignoring txs.
> > > > > > 
> > > > > > Other idea: what if you encode the parent txs as a short
> > > > > > hash of the
> > > > > > wtxid
> > > > > > (something like bip152 short ids? perhaps seeded per
> > > > > > peer so collisions
> > > > > > will
> > > > > > be different per peer?) and include that in the inv
> > > > > > announcement? Would
> > > > > > that work to avoid a round trip almost all of the time,
> > > > > > while still
> > > > > > giving
> > > > > > you
> > > > > > enough info to save bw by deduping parents?
> > > > > 
> > > > > As I suggested earlier, a package is fundamentally a
> > > > > compact block (or
> > > > > block) announcement without the header. Compact block
> > > > > (BIP152)
> > > > > announcement
> > > > > is already well-defined and widely implemented. A node
> > > > > should never be
> > > > > required to retain an orphan, and BIP152 ensures this is not
> > > > > required.
> > > > > 
> > > > > Once a validated set of txs within the package has been
> > > > > obtained with
> > > > > sufficient fee, a fee-optimal node would accept the largest
> > > > > subgraph of
> > > > > the
> > > > > package that conforms to fee constraints and drop any
> > > > > peer that provides a
> > > > > package for which the full graph does not.
> > > > > 
> > > > > Let us not reinvent the wheel and/or introduce accidental
> > > > > complexity. I
> > > > > see
> > > > > no reason why packaging is not simply BIP152 without the
> > > > > 'header' field,
> > > > > an
> > > > > updated protocol version, and the following sort of changes
> > > > > to names:
> > > > > 
> > > > > sendpkg
> > > > > MSG_CMPCT_PKG
> > > > > cmpctpkg
> > > > > getpkgtxn
> > > > > pkgtxn
> > > > > 
> > > > > > > For a maximum 25 transactions,
> > > > > > > 2324/2 = 276, seems like 36 bytes for a child-with-
> > > > > > > parents package.
> > > > > > 
> > > > > > If you're doing short ids that's maybe 254B=100B
> > > > > > already, then the
> > > > > > above
> > > > > > is
> > > > > > up to 36% overhead, I guess. Might be worth thinking
> > > > > > more about, but
> > > > > > maybe
> > > > > > more interesting with ancestors than just parents.
> > > > > > 
> > > > > > > Also side note, since there are no size/count params,
> > > > > 
> > > > > Size is restricted in the same manner as block and
> > > > > transaction broadcasts,
> > > > > by consensus. If the fee rate is sufficient there would be no
> > > > > reason to
> > > > > preclude any valid size up to what can be mined in one
> > > > > block (packaging
> > > > > across blocks is not economically rational under the
> > > > > assumption that one
> > > > > miner cannot expect to mine multiple blocks in a row).
> > > > > Count is
> > > > > incorporated
> > > > > into BIP152 as 'shortids_length'.
> > > > > 
> > > > > > > wondering if we
> > > > > > > should just have "version" in "sendpackages" be a bit
> > > > > > > field instead of
> > > > > > > sending a message for each version. 32 versions should
> > > > > > > be enough right?
> > > > > 
> > > > > Adding versioning to individual protocols is just a reflection
> > > > > of the
> > > > > insufficiency of the initial protocol versioning design, and
> > > > > that of the
> > > > > various ad-hoc changes to it (including yet another
> > > > > approach in this
> > > > > proposal) that have been introduced to compensate for it,
> > > > > though I'll
> > > > > address this in an independent post at some point.
> > > > > 
> > > > > Best,
> > > > > e
> > > > > 
> > > > > > Maybe but a couple of messages per connection doesn't
> > > > > > really seem worth
> > > > > > arguing about?
> > > > > > 
> > > > > > Cheers,
> > > > > > aj
> > > > > > 
> > > > > > --
> > > > > > Sent from my phone.
> > > > 
> > > > _______________________________________________
> > > > 
> > > > > > bitcoin-dev mailing list
> > > > > > bitcoin-dev@lists.linuxfoundation.org <mailto:bitcoin-
> > > > > > dev@lists.linuxfoundation.org>
> > > > 
> > > > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> > > > 
> > > > _______________________________________________
> > > > bitcoin-dev mailing list
> > > > bitcoin-dev@lists.linuxfoundation.org <mailto:bitcoin-
> > > > dev@lists.linuxfoundation.org>
> > > > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> > > 
> > > _______________________________________________
> > > bitcoin-dev mailing list
> > > bitcoin-dev@lists.linuxfoundation.org
> > > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev

Re: [bitcoin-dev] Packaged Transaction Relay

[eric]

> Hi Eric,
> 
> 
> This email wasn't answered by anyone on mailing list however I did some
> research about packages yesterday including this email and below are my
> observations, questions etc.

Hello, thanks for the reply.

> > The sole objective, as expressed in the OP proposal, is to:
> >
> > "Propagate transactions that are incentive-compatible to mine, even if they
> don't meet minimum feerate alone."
> 
> According to [bitcoinops][1]: Without package relay, it’s not possible to
> effectively CPFP fee bump a transaction that’s below the minimum feerate
> nodes accept.

Yes, the problem statement is not in question, just the mechanism of resolution. The problem of stuck txs arises from minimum fee rate policy, which is a necessary DOS guard.

A secondary issue is that of orphan relay. As a node must allow receipt of orphans, it has no means to differentiate a flood of unconfirmable txs from those that are confirmable.

> Matt Corallo's thoughts in a bitcoin core [issue][2]:
> 
> "Matt Corallo recently wrote about an example on the bitcoin-dev mailing list
> involving lightning transactions, where pre-signed transactions might be
> broadcast to the blockchain long after they were generated, and thus not
> have been created with a fee that is sufficient to be confirmed quickly (or
> even be accepted to node mempools). In such situations, channel
> participants may need to use chained transactions (CPFP) in order to increase
> the confirmation speed of such transactions, and that implies we may need
> to introduce a mechanism for those parent transactions to be relayed along
> with their higher feerate children, even if the parent transaction would be
> rejected by itself."

While this is a valid scenario, the problems directly affect Bitcoin. Those problems propagate to layers, but are not unique to layering.

> 1)Is it possible to have multiple pre-signed transactions with different fee
> rates in a range? Example: PSBT1: 5 sat/vbyte, PSBT2: 10 sat/vbyte, PSBT3: 20
> sat/vbyte and PSBT4: 100 sat/vbyte

If by "range" you mean a connected tx subgraph, I don't see why not. But note that nodes only operate over signed txs. PSBT is a wallet workflow.

> 2)How would covenants affect this problem?

There are a good number of covenant proposals, though I assume they are all implemented within script. If a tx is confirmable and satisfies fee rate (for DOS protection), it is relayable. Covenants affect confirmability and should not have any unique impact on relay.

> 3)How often does it happen that a pre-signed tx gets rejected by nodes
> because it did not meet the minimum fee rate? Is it predictable and could be
> managed in a different way?

Always. Only signed transactions are accepted. But assuming you are referring to a transaction that has been produced by a pre-signing workflow, I'm not sure how this would be distinct from any other tx.

> After reading several links related to packages and bitcoin core pull requests,
> I found it anti-bitcoin to introduce so much complexity because its not
> possible to CPFP fee bump a tx below minimum fee rate.

I'm not sure I follow this, maybe you could reword it. But it seems that you are saying that CPFP fee-bumping is a problem scenario and the complexity of the proposed solutions are not justified by such scenarios.

I would say that the problem is real, and that the least complex option is generally preferred. There are always tradeoffs, and balancing these is part of protocol development. But as a rule, complexity within a protocol (communication) is to be avoided where possible.

> > Furthermore any tx that is "stuck" can be freed by simply sending another
> tx. The nodes at which the tx has become stuck will just package it up and
> relay it to peers. In other words, there is no impact on wallet implementation
> apart from raising the aggregate fee using a descendant transaction.
> 
> It is easy to send another tx if there is only one user involved however
> packages are trying to fix issues in which multiple users and transaction pre-
> signed between them are involved. So, it will be difficult to coordinate and
> create new pre-signed transactions in some cases although it is possible for
> some use cases.

Given that nodes do not deal in presigned txs, this coordination difficulty could not be increased in any scenario.

A node produces sets of txs ("packages") dynamically to satisfy its peer's feerate. When a wallet broadcasts a tx/package to a node, it is operating as a peer on the p2p network. The wallet simply implements the same dynamic packaging algorithm as any peer - because it is a peer. 

> > This is barely a protocol change - it's primarily implementation. All that
> should be required is an additional INV element type, such as
> MSG_TX_PACKAGE.
> 
> > * All elements of MSG_TX_PACKAGE in one INV message MUST to be of
> the same package.
> > * A package MUST must define a set that can be mined into one block
> (size/sigops constraint).
> > * A package SHOULD not contain confirmed txs (a race may cause this).
> > * A package MUST minimally satisfy peer.feerate.
> > * A partial tx order, as in the manner of the block.txs ordering, MUST be
> imposed.
> > * A node SHOULD drop a peer that sends a package (or tx) below
> node.feerate.
> > * A node MAY drop a peer that sends a non-minimal package according to
> node.feerate.
> 
> This makes sense particularly if multiple node implementations are used in
> future.

There are many node implementations used presently. And of course these are protocol proposals, which presumes more than one implementation.

> My other questions:
> 
> a)If a package has tx1, tx2, tx3, tx4 and tx5 and miner just include tx1 and tx2
> in the block, how does this affect the projects considered for packages
> proposal?

I will leave that to authors of such proposals to answer. However in what I have proposed it just means tx3/4/5 get considered for subsequent block inclusion to the extent that fee rate policy is satisfied.

One of the several problems with static construction of packages is that they can still get stuck by fee rate policy. This is just kicking the can down the road while complicating the protocol.

> b)How does changing the order of txs in a package affect these transactions?

There is no impact. I proposed the partial ordering to facilitate fail fast.

The partial ordering in block txs is unnecessary (given the PoW DOS guard). This is a consequence of the order imposed by Satoshi's implementation and only serves to slow validation (order constrains concurrency).

> c)Do packages introduce more attack vectors in bitcoin for front running or
> MEV? MEV in bitcoin currently only affects the projects that are considered
> in packages proposal.

I don't consider this relevant to any protocol considerations. Miners should always be expected to select the most optimal set of txs available in the time available to do so.

> d)What if the package contains a transactions with sanctioned address?

One can consider this a policy, much like fee rate. Any policy that is applied to transactions and not known to its peers will result in the node receiving orphans. As such the node either must allow orphans or drop peers sending orphans under the assumption that the peer is expected to have implemented the same policy.

> e)Why would miners use packages if the existing scenario in terms of fees
> per block is beneficial for them?

The presumption is that the miner is only ever seeing txs that satisfy its fee rate policy, so this is just more opportunity.

I'd add that the problem of "pinning" is related, but exacerbated by opaque policy (internal to certain implementations). Any node that ejects txs from its pool of valid but unconfirmed txs that satisfy fee rate policy is going to see orphans and going to cause txs to get stuck. This is one of the many problems with placing an arbitrary bound on the size of this pool.

A subset of this problem is RBF policy. It is nice to see some movement toward generalizing RBF. The term is really a misnomer. Conflicting txs and subgraphs of txs are only problematic in the case of DOS, which is also resolved through advertised fee policy. Any node that imposes policy beyond this will also see orphans and cause txs to get stuck.

The scenario and therefore complexity consequences of an implementation-specific memory-constrained tx pool are becoming increasingly apparent. These are implementation issues, not protocol issues. This can be observed in a recent thread: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2022-September/020937.html

Over time we are likely to see that the only policies that remain in widespread application are those that are necessary for DOS protection (fee rate), as other restrictions are not economically rational and cannot be enforced. We've seen recent debate regarding dust policy, and op_return policy. "non-standard" txs are perfectly valid but get stuck very easily. I'll reiterate, any policy beyond what is published via the protocol will cause the above problems.

e

> /dev/fd0
> 
> [1]: https://bitcoinops.org/en/topics/package-relay/
> [2]: https://github.com/bitcoin/bitcoin/issues/14895
> 
> Sent with Proton Mail secure email.
> 
> ------- Original Message -------
> On Thursday, June 9th, 2022 at 4:13 AM, Eric Voskuil via bitcoin-dev <bitcoin-
> dev@lists.linuxfoundation.org> wrote:
> 
> 
> > Hi Suhas/Gloria,
> >
> > Good questions. I've started a new thread because it became something
> else...
> >
> > Various ideas about packaging seem to be focused on the idea of an atomic
> message that is gossiped around the network like a transaction or block.
> From my perspective that seems to create a set of problems without good
> solutions, and it is not a proper analogy to those atomic structures. It may be
> worth taking the time to step back and take a close look at the underlying
> objective.
> >
> > The sole objective, as expressed in the OP proposal, is to:
> >
> > "Propagate transactions that are incentive-compatible to mine, even if they
> don't meet minimum feerate alone."
> >
> > Effectively producing this outcome with an atomic packaging approach
> while at the same time maintaining network invariants seems unlikely, if not
> impossible.
> >
> > Fees:
> >
> > A node knows what fee rate a peer will accept, and announces individual
> txs that satisfy peer.feerate. Similarly a node knows its own feerate, and
> SHOULD drop any peer that announces txs that do not satisfy node.feerate.
> >
> > Orphans:
> >
> > A node MAY drop a peer that announces txs that the node sees as orphans
> against its DAG. It SHOULD drop the orphan tx and MAY request missing
> ancestors. Presumably after some amount of time connected to peer, node
> does not expect to see any more orphans from that peer, so these choices
> could evolve with the channel. However, the design that can only consider
> each tx in isolation will continue to cause orphan announcements on the
> channel. A below peer.feerate tx does not get announced to peer, and later
> a descendant high peer.feerate does get announced to the peer - as an
> orphan.
> >
> > BIP133 (feefilter):
> >
> > "There could be a small number of edge cases where a node's mempool
> min fee is actually less than the filter value a peer is aware of and
> transactions with fee rates between these values will now be newly
> inhibited."
> >
> > https://github.com/bitcoin/bips/blob/master/bip-0133.mediawiki
> >
> > Whether the problem is "small" or not depends on the disparity between
> node fee rates, which is not a matter of protocol. This is an existing problem
> that can and should be dealt with in packaging, as part of the above
> objective.
> >
> > Packaged Transaction Relay:
> >
> > One might instead think of packaging as a per-connection function,
> operating over its transaction (input->output) DAG and the feerate of its
> own node and that of the peer. Logically a "package" is nothing more than a
> set of transactions (optimized by announcement). Only a node can
> effectively determine the packaging required by each of its peers, since only
> the node is aware of peer.feerate.
> >
> >
> > The only way to avoid dead-ending packages (including individual
> transactions, as is the objective) is for a node to package txs for each peer.
> The origination of any package is then just a wallet peer doing what a node
> does - packaging transactions that satisfy peer.feerate (i.e. that of its node).
> >
> > Current transaction relay (txB->txA):
> >
> > ===============================
> > Node0
> > txA.feerate > node.feerate, and not orphaned (accept txA)
> >
> > txA.feerate > peer1.feerate (announce txA to peer1)
> >
> > txA.feerate < peer2.feerate (do not announce txA to peer2)
> > -----
> > txB.feerate > node.feerate (accept txB)
> >
> > txB.feerate > peer1.feerate (announce txB to peer1)
> >
> > txB.feerate > peer2.feerate (announce txB to peer2)
> >
> >
> > Node1
> > Sees/accepts txA and txB.
> >
> > Node2
> > Never sees txA, sees/rejects txB (as an orphan).
> >
> > Packaged transaction relay (txB->txA):
> >
> > ===============================
> > Node0
> > txA.feerate > node.feerate, and not orphaned (accept txA)
> >
> > txA.feerate > peer1.feerate (announce txA to peer1)
> >
> > txA.feerate < peer2.feerate (do not announce txA to peer2)
> > -----
> > txB.feerate > node1.feerate (accept txB)
> >
> > txB.feerate > peer1.feerate (announce txB to peer1)
> >
> > txB.feerate > peer2.feerate (do not announce txB to peer2) <== avoid
> > predictable orphan
> >
> > txA.feerate + txB.feerate > peer2.feerate (announce pkg(A, B) to
> > peer2) <= create minimal package
> >
> >
> > Node1
> > Sees/accepts txA and txB.
> >
> > Node2
> > pkg(A, B) > node2.feerate (accept txA, txB)
> >
> > txA.feerate > peer3.feerate (announce txA to peer3)
> >
> > txB.feerate > peer3.feerate (announce txB to peer3)
> >
> >
> > Sees/accepts pkg(A, B).
> >
> > Node3
> > Sees/accepts txA and txB. <= avoided unnecessary packaging
> >
> > Summary:
> >
> > In this design, any node that receives an announcement for a pkg (or tx)
> later determined to be less than node.feerate SHOULD drop the announcing
> peer. Unlike with existing tx relay, a node can become "current" and
> subsequently see few if any tx or pkg orphans, and MAY at some point
> decide to drop any peer that announces one. Notice that packages are
> created dynamically, and any package that doesn't need to be grouped gets
> trimmed down to individual transactions. Furthermore any tx that is "stuck"
> can be freed by simply sending another tx. The nodes at which the tx has
> become stuck will just package it up and relay it to peers. In other words,
> there is no impact on wallet implementation apart from raising the aggregate
> fee using a descendant transaction.
> >
> > This is barely a protocol change - it's primarily implementation. All that
> should be required is an additional INV element type, such as
> MSG_TX_PACKAGE.
> >
> > Additional constraints:
> >
> > * All elements of MSG_TX_PACKAGE in one INV message MUST to be of
> the same package.
> > * A package MUST must define a set that can be mined into one block
> (size/sigops constraint).
> > * A package SHOULD not contain confirmed txs (a race may cause this).
> > * A package MUST minimally satisfy peer.feerate.
> > * A partial tx order, as in the manner of the block.txs ordering, MUST be
> imposed.
> > * A node SHOULD drop a peer that sends a package (or tx) below
> node.feerate.
> > * A node MAY drop a peer that sends a non-minimal package according to
> node.feerate.
> >
> > The partial ordering of block.txs introduces an ordering constraint that
> precludes full parallelism in validating input attachment. This is an
> implementation artifact that made its way into consensus. However in the
> case of packaging, the set of txs is not presumed to be valid under the proof
> of work DoS guard. As such constraints should minimize the work/traffic
> required to invalidate the message. The partial order constraint ensures that
> the DAG can be built incrementally, dropping the attempt (and peer as
> desired) as soon as the first orphan is discovered. As a result the network
> traffic and work required is not materially different than with tx relay, with
> two exceptions.
> >
> > These are the two central aspects of this approach (Avoiding Predictable
> Orphans and Creating Minimal Packages). These are graph search algorithms,
> some basic computer science. Minimality requires only that the package does
> not introduce txs that are not necessary to reach the peer.feerate (as these
> can always be packaged separately). It does not require that nodes all
> generate the same packages. It does not require negotiation, package
> identity, cryptography, or hashing. As a graph search it should be O(n) where
> n is the unconfirmed ancestry of the package, but should typically be much
> lower, if not a single step.
> >
> > Sufficiently-low-fee nodes will see only single txs. Moderate-fee
> > nodes may cause partial breakup of packages. Sufficiently high fee
> > nodes will cause peers (having received and completed the acceptance
> > of a tx/pkg with pkg.feerate < peer.feerate) to navigate from each
> > tx/package external input until reaching txs above peer.feerate, or
> > confirmed (both of which the peer is presumed to already have). If the
> > pkg.feerate is sufficiently high to connect all external inputs to the
> > intervening txs, they are added to the package and it is announced to
> > the high fee peer. Note that the individual tx.feerate > peer.feerate
> > is insufficient to ensure that the peer should have the tx, as there
> > may be ancestor txs that do not, and for which the tx was insufficient
> > to cause them to be packaged. So a non-caching algorithm must be able
> > to chase each package external input to a confirmed tx (or cache the
> > unconfirmed ancestry fee rate at each tx). Note that fee rates are not
> > directly additive, both size/
> >
> > weight and fee are required for summation (and aggregate sigops should
> be considered).
> >
> > This makes no assumptions about current implementations. The design
> would call for maintenance of a transaction (input->output) DAG with
> tx.feerate on each tx. This could be the unconfirmed tx graph (i.e. "memory
> pool") though it does not require maintenance of anything more than the
> parameters necessary to confirm a set of validated txs within a block. It is
> very reasonable to require this of any participating node. A simple version
> negotiation can identify a package-accepting/sending nodes.
> >
> >
> > I have thought about this for some time, but have not implemented either
> the graph search, source code, or BIP. Just wrote this off the top of my head.
> So I am sure there are some things I have incorrect or failed to consider. But I
> think it's worth discussing it at this point.
> >
> > e
> >
> > > -----Original Message-----
> > > From: bitcoin-dev bitcoin-dev-bounces@lists.linuxfoundation.org On
> > > Behalf Of Suhas Daftuar via bitcoin-dev
> > > Sent: Wednesday, June 8, 2022 8:59 AM
> > > To: Bitcoin Protocol Discussion
> > > bitcoin-dev@lists.linuxfoundation.org
> > > Subject: Re: [bitcoin-dev] Package Relay Proposal
> > >
> > > Hi,
> > >
> > > Thanks again for your work on this!
> > >
> > > One question I have is about potential bandwidth waste in the case
> > > of nodes running with different policy rules. Here's my
> > > understanding of a scenario I think could happen:
> > >
> > > 1) Transaction A is both low-fee and non-standard to some nodes on
> > > the network.
> > > 2) Whenever a transaction T that spends A is relayed, new nodes will
> > > send INV(PKGINFO1, T) to all package-relay peers.
> > > 3) Nodes on the network that have implemented package relay, but do
> > > not accept A, will send getdata(PKGINFO1, T) and learn all of T's
> > > unconfirmed parents (~32 bytes * number of parents(T)).
> > > 4) Such nodes will reject T. But because of transaction
> > > malleability, and to avoid being blinded to a transaction
> > > unnecessarily, these nodes will likely still send getdata(PKGINFO1,
> > > T) to every node that announces T, in case someone has a transaction
> > > that includes an alternate set of parent transactions that would pass
> policy checks.
> > >
> > > Is that understanding correct? I think a good design goal would be
> > > to not waste bandwidth in non-adversarial situations. In this case,
> > > there would be bandwidth waste from downloading duplicate data from
> > > all your peers, just because the announcement doesn't commit to the
> > > set of parent wtxids that we'd get from the peer (and so we are
> > > unable to determine that all our peers would be telling us the same thing,
> just based on the announcement).
> > >
> > > Some ways to mitigate this might be to: (a) include a hash (maybe
> > > even just a 20-byte hash -- is that enough security?) of the package
> > > wtxids (in some canonical ordering) along with the wtxid of the
> > > child in the initial announcement; (b) limit the use of v1 packages
> > > to transactions with very few parents (I don't know if this is reasonable
> for the use cases we have in mind).
> > >
> > > Another point I wanted to bring up is about the rules around v1
> > > package validation generally, and the use of a blockhash in
> > > transaction relay specifically. My first observation is that it
> > > won't always be the case that a v1 package relay node will be able
> > > to validate that a set of package transactions is fully sorted
> > > topologically, because there may be (non-parent) ancestors that are
> > > missing from the package and the best a peer can validate is
> > > topology within the package -- this means that a peer can validly
> > > (under this
> > > BIP) relay transaction packages out of the true topological sort (if
> > > all ancestors were included).
> > >
> > > This makes me wonder how useful this topological rule is. I suppose
> > > there is some value in preventing completely broken implementations
> > > from staying connected and so there is no harm in having the rule,
> > > but perhaps it would be helpful to add that nodes SHOULD order
> > > transactions based on topological sort in the complete transaction
> > > graph, so that if missing-from-package ancestors are already known
> > > by a peer (which is the expected case when using v1 package relay on
> > > transactions that have more than one generation of unconfirmed
> > > ancestor) then the remaining transactions are already properly ordered,
> and this is helpful even if unenforceable in general.
> > >
> > > The other observation I wanted to make was that having transaction
> > > relay gated on whether two nodes agree on chain tip seems like an
> > > overly restrictive criteria. I think an important design principle
> > > is that we want to minimize disruption from network splits -- if
> > > there are competing blocks found in a small window of time, it's
> > > likely that the utxo set is not materially different on the two
> > > chains (assuming miners are selecting from roughly the same sets of
> > > transactions when this happens, which is typical). Having
> > > transaction relay bifurcate on the two network halves would seem to
> > > exacerbate the difference between the two sides of the split --
> > > users ought to be agnostic about how benign splits are resolved and
> would likely want their transactions to relay across the whole network.
> > >
> > > Additionally, use of a chain tip might impose a larger burden than
> > > is necessary on software that would seek to participate in
> > > transaction relay without implementing headers sync/validation. I
> > > don't know what software exists on the network, but I imagine there
> > > are a lot of scripts out there for transaction submission to the
> > > public p2p network, and in thinking about modifying such a script to
> > > utilize package relay it seems like an unnecessary added burden to first
> learn a node's tip before trying to relay a transaction.
> > >
> > > Could you explain again what the benefit of including the blockhash
> > > is? It seems like it is just so that a node could prioritize
> > > transaction relay from peers with the same chain tip to maximize the
> > > likelihood of transaction acceptance, but in the common case this
> > > seems like a pretty negligible concern, and in the case of a chain
> > > fork that persists for many minutes it seems better to me that we
> > > not partition the network into package-relay regimes and just risk a
> > > little extra bandwidth in one direction or the other. If we solve
> > > the problem I brought up at the beginning (of de-duplicating package
> > > data across peers with a package-wtxid-commitment in the
> > > announcement), I think this is just some wasted pkginfo bandwidth on
> > > a single-link, and not across links (as we could cache validation failure for a
> package-hash to avoid re-requesting duplicate pkginfo1 messages).
> > >
> > > Best,
> > > Suhas
> > >
> > > On Tue, Jun 7, 2022 at 1:57 PM Gloria Zhao via bitcoin-dev <bitcoin-
> > > dev@lists.linuxfoundation.org <mailto:bitcoin-
> > > dev@lists.linuxfoundation.org> > wrote:
> > >
> > > Hi Eric, aj, all,
> > >
> > > Sorry for the delayed response. @aj I'm including some paraphrased
> > > points from our offline discussion (thanks).
> > >
> > > > Other idea: what if you encode the parent txs as a short hash of
> > > > the wtxid (something like bip152 short ids? perhaps seeded per
> > > > peer so collisions will be different per peer?) and include that in the inv
> announcement?
> > > > Would that work to avoid a round trip almost all of the time,
> > > > while still giving you enough info to save bw by deduping parents?
> > >
> > > > As I suggested earlier, a package is fundamentally a compact block
> > > > (or
> > > > block) announcement without the header. Compact block (BIP152)
> > > > announcement is already well-defined and widely implemented...
> > >
> > > > Let us not reinvent the wheel and/or introduce accidental
> > > > complexity. I see no reason why packaging is not simply BIP152
> > > > without the 'header'
> > > > field, an
> > > > updated protocol version, and the following sort of changes to
> > > > names
> > >
> > > Interestingly, "why not use BIP 152 shortids to save bandwidth?" is
> > > by far the most common suggestion I hear (including offline feedback).
> > > Here's a full explanation:
> > >
> > > BIP 152 shortens transaction hashes (32 bytes) to shortids (6 bytes)
> > > to save a significant amount of network bandwidth, which is
> > > extremely important in block relay. However, this comes at the
> > > expense of computational complexity. There is no way to directly
> > > calculate a transaction hash from a shortid; upon receipt of a
> > > compact block, a node is expected to calculate the shortids of every
> > > unconfirmed transaction it knows about to find the matches (BIP 152:
> > > 1, Bitcoin Core: [2]). This is expensive but appropriate for block
> > > relay, since the block must have a valid Proof of Work and new
> > > blocks only come every ~10 minutes. On the other hand, if we require
> > > nodes to calculate shortids for every transaction in their mempools every
> time they receive a package, we are creating a DoS vector.
> > > Unconfirmed transactions don't need PoW and, to have a live
> > > transaction relay network, we should expect nodes to handle
> > > transactions at a high-ish rate (i.e. at least 1000s of times more
> > > transactions than blocks). We can't pre- calculate or cache shortids
> > > for mempool transactions, since the SipHash key depends on the block
> hash and a per-connection salt.
> > >
> > > Additionally, shortid calculation is not designed to prevent
> > > intentional individual collisions. If we were to use these shortids
> > > to deduplicate transactions we've supposedly already seen, we may
> > > have a censorship vector. Again, these tradeoffs make sense for
> > > compact block relay (see shortid section in BIP 152 [3]), but not package
> relay.
> > >
> > > TLDR: DoSy if we calculate shortids on every package and censorship
> > > vector if we use shortids for deduplication.
> > >
> > > > Given this message there is no reason to send a (potentially
> > > > bogus) fee rate with every package. It can only be validated by
> > > > obtaining the full set of txs, and the only recourse is dropping
> > > > (etc.) the peer, as is the case with single txs.
> > >
> > > Yeah, I agree with this. Combined with the previous discussion with
> > > aj (i.e. we can't accurately communicate the incentive compatibility
> > > of a package without sending the full graph, and this whole dance is
> > > to avoid downloading a few low-fee transactions in uncommon edge
> > > cases), I've realized I should remove the fee + weight information
> > > from pkginfo. Yay for less complexity!
> > >
> > > Also, this might be pedantic, but I said something incorrect earlier
> > > and would like to correct myself:
> > >
> > > > > In theory, yes, but maybe it was announced earlier (while our
> > > > > node was down?) or had dropped from our mempool or similar,
> > > > > either way we don't have those txs yet.
> > >
> > > I said "It's fine if they have Erlay, since a sender would know in
> > > advance that B is missing and announce it as a package." But this
> > > isn't true since we're only using reconciliation in place of
> > > flooding to announce transactions as they arrive, not for
> > > rebroadcast, and we're not doing full mempool set reconciliation. In
> > > any case, making sure a node receives the transactions announced
> > > when it was offline is not something we guarantee, not an intended use
> case for package relay, and not worsened by this.
> > >
> > > Thanks for your feedback!
> > >
> > > Best,
> > >
> > > Gloria
> > >
> > > 0152.mediawiki#cmpctblock
> > > [2]:
> > > https://github.com/bitcoin/bitcoin/blob/master/src/blockencodings.cp
> > > p#L49
> > > [3]: https://github.com/bitcoin/bips/blob/master/bip-
> > > 0152.mediawiki#short-transaction-id-calculation
> > >
> > > On Thu, May 26, 2022 at 3:59 AM <eric@voskuil.org
> > > mailto:eric@voskuil.org > wrote:
> > >
> > > Given that packages have no header, the package requires identity in
> > > a
> > > BIP152 scheme. For example 'header' and 'blockhash' fields can be
> > > replaced with a Merkle root (e.g. "identity" field) for the package,
> > > uniquely identifying the partially-ordered set of txs. And use of
> > > 'getdata' (to obtain a package by hash) can be eliminated (not a use
> > > case).
> > >
> > > e
> > >
> > > > -----Original Message-----
> > > > From: eric@voskuil.org mailto:eric@voskuil.org
> > > <eric@voskuil.org mailto:eric@voskuil.org >
> > > > Sent: Wednesday, May 25, 2022 1:52 PM
> > > > To: 'Anthony Towns' <aj@erisian.com.au
> > > mailto:aj@erisian.com.au >; 'Bitcoin Protocol Discussion'
> > > > <bitcoin-dev@lists.linuxfoundation.org <mailto:bitcoin-
> > > dev@lists.linuxfoundation.org> >; 'Gloria Zhao'
> > > > <gloriajzhao@gmail.com mailto:gloriajzhao@gmail.com >
> > > > Subject: RE: [bitcoin-dev] Package Relay Proposal
> > > >
> > > > > From: bitcoin-dev <bitcoin-dev-
> > > bounces@lists.linuxfoundation.org <mailto:bitcoin-dev-
> > > bounces@lists.linuxfoundation.org> > On
> > > > Behalf
> > > > > Of Anthony Towns via bitcoin-dev
> > > > > Sent: Wednesday, May 25, 2022 11:56 AM
> > > >
> > > > > So the other thing is what happens if the peer
> > > announcing packages to us
> > > > is
> > > > > dishonest?
> > > > >
> > > > > They announce pkg X, say X has parents A B C and the fee
> > > rate is
> > > garbage.
> > > > But
> > > > > actually X has parent D and the fee rate is excellent. Do
> > > we request the
> > > > > package from another peer, or every peer, to double
> > > check? Otherwise
> > > > we're
> > > > > allowing the first peer we ask about a package to censor
> > > that tx from
> > > us?
> > > > >
> > > > > I think the fix for that is just to provide the fee and weight
> > > when
> > > > announcing
> > > > > the package rather than only being asked for its info?
> > > Then if one peer
> > > > makes
> > > > > it sound like a good deal you ask for the parent txids from
> > > them,
> > > dedupe,
> > > > > request, and verify they were honest about the parents.
> > > >
> > > > Single tx broadcasts do not carry an advertised fee rate,
> > > however the'
> > > > feefilter' message (BIP133) provides this distinction. This
> > > should be
> > > > interpreted as applicable to packages. Given this message
> > > there is no
> > > reason
> > > > to send a (potentially bogus) fee rate with every package. It
> > > can only be
> > > > validated by obtaining the full set of txs, and the only
> > > recourse is
> > > > dropping (etc.) the peer, as is the case with single txs.
> > > Relying on the
> > > > existing message is simpler, more consistent, and more
> > > efficient.
> > > >
> > > > > >> Is it plausible to add the graph in?
> > > > >
> > > > > Likewise, I think you'd have to have the graph info from
> > > many nodes if
> > > > you're
> > > > > going to make decisions based on it and don't want
> > > hostile peers to be
> > > > able to
> > > > > trick you into ignoring txs.
> > > > >
> > > > > Other idea: what if you encode the parent txs as a short
> > > hash of the
> > > wtxid
> > > > > (something like bip152 short ids? perhaps seeded per
> > > peer so collisions
> > > > will
> > > > > be different per peer?) and include that in the inv
> > > announcement? Would
> > > > > that work to avoid a round trip almost all of the time,
> > > while still
> > > giving
> > > > you
> > > > > enough info to save bw by deduping parents?
> > > >
> > > > As I suggested earlier, a package is fundamentally a
> > > compact block (or
> > > > block) announcement without the header. Compact block
> > > (BIP152)
> > > > announcement
> > > > is already well-defined and widely implemented. A node
> > > should never be
> > > > required to retain an orphan, and BIP152 ensures this is not
> > > required.
> > > >
> > > > Once a validated set of txs within the package has been
> > > obtained with
> > > > sufficient fee, a fee-optimal node would accept the largest
> > > subgraph of
> > > the
> > > > package that conforms to fee constraints and drop any
> > > peer that provides a
> > > > package for which the full graph does not.
> > > >
> > > > Let us not reinvent the wheel and/or introduce accidental
> > > complexity. I
> > > see
> > > > no reason why packaging is not simply BIP152 without the
> > > 'header' field,
> > > an
> > > > updated protocol version, and the following sort of changes
> > > to names:
> > > >
> > > > sendpkg
> > > > MSG_CMPCT_PKG
> > > > cmpctpkg
> > > > getpkgtxn
> > > > pkgtxn
> > > >
> > > > > > For a maximum 25 transactions,
> > > > > >2324/2 = 276, seems like 36 bytes for a child-with-
> > > parents package.
> > > > >
> > > > > If you're doing short ids that's maybe 254B=100B
> > > already, then the
> > > above
> > > > is
> > > > > up to 36% overhead, I guess. Might be worth thinking
> > > more about, but
> > > > maybe
> > > > > more interesting with ancestors than just parents.
> > > > >
> > > > > >Also side note, since there are no size/count params,
> > > >
> > > > Size is restricted in the same manner as block and
> > > transaction broadcasts,
> > > > by consensus. If the fee rate is sufficient there would be no
> > > reason to
> > > > preclude any valid size up to what can be mined in one
> > > block (packaging
> > > > across blocks is not economically rational under the
> > > assumption that one
> > > > miner cannot expect to mine multiple blocks in a row).
> > > Count is
> > > incorporated
> > > > into BIP152 as 'shortids_length'.
> > > >
> > > > > > wondering if we
> > > > > >should just have "version" in "sendpackages" be a bit
> > > field instead of
> > > > > >sending a message for each version. 32 versions should
> > > be enough right?
> > > >
> > > > Adding versioning to individual protocols is just a reflection
> > > of the
> > > > insufficiency of the initial protocol versioning design, and
> > > that of the
> > > > various ad-hoc changes to it (including yet another
> > > approach in this
> > > > proposal) that have been introduced to compensate for it,
> > > though I'll
> > > > address this in an independent post at some point.
> > > >
> > > > Best,
> > > > e
> > > >
> > > > > Maybe but a couple of messages per connection doesn't
> > > really seem worth
> > > > > arguing about?
> > > > >
> > > > > Cheers,
> > > > > aj
> > > > >
> > > > >
> > > > > --
> > > > > Sent from my phone.
> > > > >
> > > _______________________________________________
> > > > > bitcoin-dev mailing list
> > > > > bitcoin-dev@lists.linuxfoundation.org <mailto:bitcoin-
> > > dev@lists.linuxfoundation.org>
> > > > >
> > > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> > >
> > > _______________________________________________
> > > bitcoin-dev mailing list
> > > bitcoin-dev@lists.linuxfoundation.org <mailto:bitcoin-
> > > dev@lists.linuxfoundation.org>
> > > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> >
> >
> >
> > _______________________________________________
> > bitcoin-dev mailing list
> > bitcoin-dev@lists.linuxfoundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev

Re: [bitcoin-dev] Packaged Transaction Relay

[alicexbt]

Hi Eric,


This email wasn't answered by anyone on mailing list however I did some research about packages yesterday including this email and below are my observations, questions etc.

> The sole objective, as expressed in the OP proposal, is to:
> 
> "Propagate transactions that are incentive-compatible to mine, even if they don't meet minimum feerate alone."


According to [bitcoinops][1]: Without package relay, it’s not possible to effectively CPFP fee bump a transaction that’s below the minimum feerate nodes accept.

Matt Corallo's thoughts in a bitcoin core [issue][2]:

"Matt Corallo recently wrote about an example on the bitcoin-dev mailing list involving lightning transactions, where pre-signed transactions might be broadcast to the blockchain long after they were generated, and thus not have been created with a fee that is sufficient to be confirmed quickly (or even be accepted to node mempools). In such situations, channel participants may need to use chained transactions (CPFP) in order to increase the confirmation speed of such transactions, and that implies we may need to introduce a mechanism for those parent transactions to be relayed along with their higher feerate children, even if the parent transaction would be rejected by itself."

1)Is it possible to have multiple pre-signed transactions with different fee rates in a range? Example: PSBT1: 5 sat/vbyte, PSBT2: 10 sat/vbyte, PSBT3: 20 sat/vbyte and PSBT4: 100 sat/vbyte
2)How would covenants affect this problem?
3)How often does it happen that a pre-signed tx gets rejected by nodes because it did not meet the minimum fee rate? Is it predictable and could be managed in a different way?

After reading several links related to packages and bitcoin core pull requests, I found it anti-bitcoin to introduce so much complexity because its not possible to CPFP fee bump a tx below minimum fee rate. 


> Furthermore any tx that is "stuck" can be freed by simply sending another tx. The nodes at which the tx has become stuck will just package it up and relay it to peers. In other words, there is no impact on wallet implementation apart from raising the aggregate fee using a descendant transaction.

It is easy to send another tx if there is only one user involved however packages are trying to fix issues in which multiple users and transaction pre-signed between them are involved. So, it will be difficult to coordinate and create new pre-signed transactions in some cases although it is possible for some use cases.


> This is barely a protocol change - it's primarily implementation. All that should be required is an additional INV element type, such as MSG_TX_PACKAGE.

> * All elements of MSG_TX_PACKAGE in one INV message MUST to be of the same package.
> * A package MUST must define a set that can be mined into one block (size/sigops constraint).
> * A package SHOULD not contain confirmed txs (a race may cause this).
> * A package MUST minimally satisfy peer.feerate.
> * A partial tx order, as in the manner of the block.txs ordering, MUST be imposed.
> * A node SHOULD drop a peer that sends a package (or tx) below node.feerate.
> * A node MAY drop a peer that sends a non-minimal package according to node.feerate.

This makes sense particularly if multiple node implementations are used in future. 

My other questions:

a)If a package has tx1, tx2, tx3, tx4 and tx5 and miner just include tx1 and tx2 in the block, how does this affect the projects considered for packages proposal?

b)How does changing the order of txs in a package affect these transactions?

c)Do packages introduce more attack vectors in bitcoin for front running or MEV? MEV in bitcoin currently only affects the projects that are considered in packages proposal.

d)What if the package contains a transactions with sanctioned address?

e)Why would miners use packages if the existing scenario in terms of fees per block is beneficial for them?


/dev/fd0

[1]: https://bitcoinops.org/en/topics/package-relay/
[2]: https://github.com/bitcoin/bitcoin/issues/14895

Sent with Proton Mail secure email.

------- Original Message -------
On Thursday, June 9th, 2022 at 4:13 AM, Eric Voskuil via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:


> Hi Suhas/Gloria,
> 
> Good questions. I've started a new thread because it became something else...
> 
> Various ideas about packaging seem to be focused on the idea of an atomic message that is gossiped around the network like a transaction or block. From my perspective that seems to create a set of problems without good solutions, and it is not a proper analogy to those atomic structures. It may be worth taking the time to step back and take a close look at the underlying objective.
> 
> The sole objective, as expressed in the OP proposal, is to:
> 
> "Propagate transactions that are incentive-compatible to mine, even if they don't meet minimum feerate alone."
> 
> Effectively producing this outcome with an atomic packaging approach while at the same time maintaining network invariants seems unlikely, if not impossible.
> 
> Fees:
> 
> A node knows what fee rate a peer will accept, and announces individual txs that satisfy peer.feerate. Similarly a node knows its own feerate, and SHOULD drop any peer that announces txs that do not satisfy node.feerate.
> 
> Orphans:
> 
> A node MAY drop a peer that announces txs that the node sees as orphans against its DAG. It SHOULD drop the orphan tx and MAY request missing ancestors. Presumably after some amount of time connected to peer, node does not expect to see any more orphans from that peer, so these choices could evolve with the channel. However, the design that can only consider each tx in isolation will continue to cause orphan announcements on the channel. A below peer.feerate tx does not get announced to peer, and later a descendant high peer.feerate does get announced to the peer - as an orphan.
> 
> BIP133 (feefilter):
> 
> "There could be a small number of edge cases where a node's mempool min fee is actually less than the filter value a peer is aware of and transactions with fee rates between these values will now be newly inhibited."
> 
> https://github.com/bitcoin/bips/blob/master/bip-0133.mediawiki
> 
> Whether the problem is "small" or not depends on the disparity between node fee rates, which is not a matter of protocol. This is an existing problem that can and should be dealt with in packaging, as part of the above objective.
> 
> Packaged Transaction Relay:
> 
> One might instead think of packaging as a per-connection function, operating over its transaction (input->output) DAG and the feerate of its own node and that of the peer. Logically a "package" is nothing more than a set of transactions (optimized by announcement). Only a node can effectively determine the packaging required by each of its peers, since only the node is aware of peer.feerate.
> 
> 
> The only way to avoid dead-ending packages (including individual transactions, as is the objective) is for a node to package txs for each peer. The origination of any package is then just a wallet peer doing what a node does - packaging transactions that satisfy peer.feerate (i.e. that of its node).
> 
> Current transaction relay (txB->txA):
> 
> ===============================
> Node0
> txA.feerate > node.feerate, and not orphaned (accept txA)
> 
> txA.feerate > peer1.feerate (announce txA to peer1)
> 
> txA.feerate < peer2.feerate (do not announce txA to peer2)
> -----
> txB.feerate > node.feerate (accept txB)
> 
> txB.feerate > peer1.feerate (announce txB to peer1)
> 
> txB.feerate > peer2.feerate (announce txB to peer2)
> 
> 
> Node1
> Sees/accepts txA and txB.
> 
> Node2
> Never sees txA, sees/rejects txB (as an orphan).
> 
> Packaged transaction relay (txB->txA):
> 
> ===============================
> Node0
> txA.feerate > node.feerate, and not orphaned (accept txA)
> 
> txA.feerate > peer1.feerate (announce txA to peer1)
> 
> txA.feerate < peer2.feerate (do not announce txA to peer2)
> -----
> txB.feerate > node1.feerate (accept txB)
> 
> txB.feerate > peer1.feerate (announce txB to peer1)
> 
> txB.feerate > peer2.feerate (do not announce txB to peer2) <== avoid predictable orphan
> 
> txA.feerate + txB.feerate > peer2.feerate (announce pkg(A, B) to peer2) <= create minimal package
> 
> 
> Node1
> Sees/accepts txA and txB.
> 
> Node2
> pkg(A, B) > node2.feerate (accept txA, txB)
> 
> txA.feerate > peer3.feerate (announce txA to peer3)
> 
> txB.feerate > peer3.feerate (announce txB to peer3)
> 
> 
> Sees/accepts pkg(A, B).
> 
> Node3
> Sees/accepts txA and txB. <= avoided unnecessary packaging
> 
> Summary:
> 
> In this design, any node that receives an announcement for a pkg (or tx) later determined to be less than node.feerate SHOULD drop the announcing peer. Unlike with existing tx relay, a node can become "current" and subsequently see few if any tx or pkg orphans, and MAY at some point decide to drop any peer that announces one. Notice that packages are created dynamically, and any package that doesn't need to be grouped gets trimmed down to individual transactions. Furthermore any tx that is "stuck" can be freed by simply sending another tx. The nodes at which the tx has become stuck will just package it up and relay it to peers. In other words, there is no impact on wallet implementation apart from raising the aggregate fee using a descendant transaction.
> 
> This is barely a protocol change - it's primarily implementation. All that should be required is an additional INV element type, such as MSG_TX_PACKAGE.
> 
> Additional constraints:
> 
> * All elements of MSG_TX_PACKAGE in one INV message MUST to be of the same package.
> * A package MUST must define a set that can be mined into one block (size/sigops constraint).
> * A package SHOULD not contain confirmed txs (a race may cause this).
> * A package MUST minimally satisfy peer.feerate.
> * A partial tx order, as in the manner of the block.txs ordering, MUST be imposed.
> * A node SHOULD drop a peer that sends a package (or tx) below node.feerate.
> * A node MAY drop a peer that sends a non-minimal package according to node.feerate.
> 
> The partial ordering of block.txs introduces an ordering constraint that precludes full parallelism in validating input attachment. This is an implementation artifact that made its way into consensus. However in the case of packaging, the set of txs is not presumed to be valid under the proof of work DoS guard. As such constraints should minimize the work/traffic required to invalidate the message. The partial order constraint ensures that the DAG can be built incrementally, dropping the attempt (and peer as desired) as soon as the first orphan is discovered. As a result the network traffic and work required is not materially different than with tx relay, with two exceptions.
> 
> These are the two central aspects of this approach (Avoiding Predictable Orphans and Creating Minimal Packages). These are graph search algorithms, some basic computer science. Minimality requires only that the package does not introduce txs that are not necessary to reach the peer.feerate (as these can always be packaged separately). It does not require that nodes all generate the same packages. It does not require negotiation, package identity, cryptography, or hashing. As a graph search it should be O(n) where n is the unconfirmed ancestry of the package, but should typically be much lower, if not a single step.
> 
> Sufficiently-low-fee nodes will see only single txs. Moderate-fee nodes may cause partial breakup of packages. Sufficiently high fee nodes will cause peers (having received and completed the acceptance of a tx/pkg with pkg.feerate < peer.feerate) to navigate from each tx/package external input until reaching txs above peer.feerate, or confirmed (both of which the peer is presumed to already have). If the pkg.feerate is sufficiently high to connect all external inputs to the intervening txs, they are added to the package and it is announced to the high fee peer. Note that the individual tx.feerate > peer.feerate is insufficient to ensure that the peer should have the tx, as there may be ancestor txs that do not, and for which the tx was insufficient to cause them to be packaged. So a non-caching algorithm must be able to chase each package external input to a confirmed tx (or cache the unconfirmed ancestry fee rate at each tx). Note that fee rates are not directly additive, both size/
> 
> weight and fee are required for summation (and aggregate sigops should be considered).
> 
> This makes no assumptions about current implementations. The design would call for maintenance of a transaction (input->output) DAG with tx.feerate on each tx. This could be the unconfirmed tx graph (i.e. "memory pool") though it does not require maintenance of anything more than the parameters necessary to confirm a set of validated txs within a block. It is very reasonable to require this of any participating node. A simple version negotiation can identify a package-accepting/sending nodes.
> 
> 
> I have thought about this for some time, but have not implemented either the graph search, source code, or BIP. Just wrote this off the top of my head. So I am sure there are some things I have incorrect or failed to consider. But I think it's worth discussing it at this point.
> 
> e
> 
> > -----Original Message-----
> > From: bitcoin-dev bitcoin-dev-bounces@lists.linuxfoundation.org On
> > Behalf Of Suhas Daftuar via bitcoin-dev
> > Sent: Wednesday, June 8, 2022 8:59 AM
> > To: Bitcoin Protocol Discussion bitcoin-dev@lists.linuxfoundation.org
> > Subject: Re: [bitcoin-dev] Package Relay Proposal
> > 
> > Hi,
> > 
> > Thanks again for your work on this!
> > 
> > One question I have is about potential bandwidth waste in the case of nodes
> > running with different policy rules. Here's my understanding of a scenario I
> > think could happen:
> > 
> > 1) Transaction A is both low-fee and non-standard to some nodes on the
> > network.
> > 2) Whenever a transaction T that spends A is relayed, new nodes will send
> > INV(PKGINFO1, T) to all package-relay peers.
> > 3) Nodes on the network that have implemented package relay, but do not
> > accept A, will send getdata(PKGINFO1, T) and learn all of T's unconfirmed
> > parents (~32 bytes * number of parents(T)).
> > 4) Such nodes will reject T. But because of transaction malleability, and to
> > avoid being blinded to a transaction unnecessarily, these nodes will likely still
> > send getdata(PKGINFO1, T) to every node that announces T, in case
> > someone has a transaction that includes an alternate set of parent
> > transactions that would pass policy checks.
> > 
> > Is that understanding correct? I think a good design goal would be to not
> > waste bandwidth in non-adversarial situations. In this case, there would be
> > bandwidth waste from downloading duplicate data from all your peers, just
> > because the announcement doesn't commit to the set of parent wtxids that
> > we'd get from the peer (and so we are unable to determine that all our peers
> > would be telling us the same thing, just based on the announcement).
> > 
> > Some ways to mitigate this might be to: (a) include a hash (maybe even just a
> > 20-byte hash -- is that enough security?) of the package wtxids (in some
> > canonical ordering) along with the wtxid of the child in the initial
> > announcement; (b) limit the use of v1 packages to transactions with very few
> > parents (I don't know if this is reasonable for the use cases we have in mind).
> > 
> > Another point I wanted to bring up is about the rules around v1 package
> > validation generally, and the use of a blockhash in transaction relay
> > specifically. My first observation is that it won't always be the case that a v1
> > package relay node will be able to validate that a set of package transactions
> > is fully sorted topologically, because there may be (non-parent) ancestors
> > that are missing from the package and the best a peer can validate is
> > topology within the package -- this means that a peer can validly (under this
> > BIP) relay transaction packages out of the true topological sort (if all
> > ancestors were included).
> > 
> > This makes me wonder how useful this topological rule is. I suppose there is
> > some value in preventing completely broken implementations from staying
> > connected and so there is no harm in having the rule, but perhaps it would
> > be helpful to add that nodes SHOULD order transactions based on topological
> > sort in the complete transaction graph, so that if missing-from-package
> > ancestors are already known by a peer (which is the expected case when
> > using v1 package relay on transactions that have more than one generation
> > of unconfirmed ancestor) then the remaining transactions are already
> > properly ordered, and this is helpful even if unenforceable in general.
> > 
> > The other observation I wanted to make was that having transaction relay
> > gated on whether two nodes agree on chain tip seems like an overly
> > restrictive criteria. I think an important design principle is that we want to
> > minimize disruption from network splits -- if there are competing blocks
> > found in a small window of time, it's likely that the utxo set is not materially
> > different on the two chains (assuming miners are selecting from roughly the
> > same sets of transactions when this happens, which is typical). Having
> > transaction relay bifurcate on the two network halves would seem to
> > exacerbate the difference between the two sides of the split -- users ought
> > to be agnostic about how benign splits are resolved and would likely want
> > their transactions to relay across the whole network.
> > 
> > Additionally, use of a chain tip might impose a larger burden than is necessary
> > on software that would seek to participate in transaction relay without
> > implementing headers sync/validation. I don't know what software exists on
> > the network, but I imagine there are a lot of scripts out there for transaction
> > submission to the public p2p network, and in thinking about modifying such a
> > script to utilize package relay it seems like an unnecessary added burden to
> > first learn a node's tip before trying to relay a transaction.
> > 
> > Could you explain again what the benefit of including the blockhash is? It
> > seems like it is just so that a node could prioritize transaction relay from
> > peers with the same chain tip to maximize the likelihood of transaction
> > acceptance, but in the common case this seems like a pretty negligible
> > concern, and in the case of a chain fork that persists for many minutes it
> > seems better to me that we not partition the network into package-relay
> > regimes and just risk a little extra bandwidth in one direction or the other. If
> > we solve the problem I brought up at the beginning (of de-duplicating
> > package data across peers with a package-wtxid-commitment in the
> > announcement), I think this is just some wasted pkginfo bandwidth on a
> > single-link, and not across links (as we could cache validation failure for a
> > package-hash to avoid re-requesting duplicate pkginfo1 messages).
> > 
> > Best,
> > Suhas
> > 
> > On Tue, Jun 7, 2022 at 1:57 PM Gloria Zhao via bitcoin-dev <bitcoin-
> > dev@lists.linuxfoundation.org <mailto:bitcoin-
> > dev@lists.linuxfoundation.org> > wrote:
> > 
> > Hi Eric, aj, all,
> > 
> > Sorry for the delayed response. @aj I'm including some paraphrased
> > points from our offline discussion (thanks).
> > 
> > > Other idea: what if you encode the parent txs as a short hash of the
> > > wtxid (something like bip152 short ids? perhaps seeded per peer so collisions
> > > will be different per peer?) and include that in the inv announcement?
> > > Would that work to avoid a round trip almost all of the time, while still giving
> > > you enough info to save bw by deduping parents?
> > 
> > > As I suggested earlier, a package is fundamentally a compact block
> > > (or
> > > block) announcement without the header. Compact block (BIP152)
> > > announcement
> > > is already well-defined and widely implemented...
> > 
> > > Let us not reinvent the wheel and/or introduce accidental
> > > complexity. I see
> > > no reason why packaging is not simply BIP152 without the 'header'
> > > field, an
> > > updated protocol version, and the following sort of changes to
> > > names
> > 
> > Interestingly, "why not use BIP 152 shortids to save bandwidth?" is
> > by far the most common suggestion I hear (including offline feedback).
> > Here's a full explanation:
> > 
> > BIP 152 shortens transaction hashes (32 bytes) to shortids (6 bytes)
> > to save a significant amount of network bandwidth, which is extremely
> > important in block relay. However, this comes at the expense of
> > computational complexity. There is no way to directly calculate a transaction
> > hash from a shortid; upon receipt of a compact block, a node is expected to
> > calculate the shortids of every unconfirmed transaction it knows about to
> > find the matches (BIP 152: 1, Bitcoin Core: [2]). This is expensive but
> > appropriate for block relay, since the block must have a valid Proof of Work
> > and new blocks only come every ~10 minutes. On the other hand, if we
> > require nodes to calculate shortids for every transaction in their mempools
> > every time they receive a package, we are creating a DoS vector.
> > Unconfirmed transactions don't need PoW and, to have a live transaction
> > relay network, we should expect nodes to handle transactions at a high-ish
> > rate (i.e. at least 1000s of times more transactions than blocks). We can't pre-
> > calculate or cache shortids for mempool transactions, since the SipHash key
> > depends on the block hash and a per-connection salt.
> > 
> > Additionally, shortid calculation is not designed to prevent intentional
> > individual collisions. If we were to use these shortids to deduplicate
> > transactions we've supposedly already seen, we may have a censorship
> > vector. Again, these tradeoffs make sense for compact block relay (see
> > shortid section in BIP 152 [3]), but not package relay.
> > 
> > TLDR: DoSy if we calculate shortids on every package and censorship
> > vector if we use shortids for deduplication.
> > 
> > > Given this message there is no reason
> > > to send a (potentially bogus) fee rate with every package. It can
> > > only be
> > > validated by obtaining the full set of txs, and the only recourse is
> > > dropping (etc.) the peer, as is the case with single txs.
> > 
> > Yeah, I agree with this. Combined with the previous discussion with
> > aj (i.e. we can't accurately communicate the incentive compatibility of a
> > package without sending the full graph, and this whole dance is to avoid
> > downloading a few low-fee transactions in uncommon edge cases), I've
> > realized I should remove the fee + weight information from pkginfo. Yay for
> > less complexity!
> > 
> > Also, this might be pedantic, but I said something incorrect earlier
> > and would like to correct myself:
> > 
> > > > In theory, yes, but maybe it was announced earlier (while our
> > > > node was down?) or had dropped from our mempool or similar, either way
> > > > we don't have those txs yet.
> > 
> > I said "It's fine if they have Erlay, since a sender would know in
> > advance that B is missing and announce it as a package." But this isn't true
> > since we're only using reconciliation in place of flooding to announce
> > transactions as they arrive, not for rebroadcast, and we're not doing full
> > mempool set reconciliation. In any case, making sure a node receives the
> > transactions announced when it was offline is not something we guarantee,
> > not an intended use case for package relay, and not worsened by this.
> > 
> > Thanks for your feedback!
> > 
> > Best,
> > 
> > Gloria
> > 
> > 0152.mediawiki#cmpctblock
> > [2]:
> > https://github.com/bitcoin/bitcoin/blob/master/src/blockencodings.cpp#L49
> > [3]: https://github.com/bitcoin/bips/blob/master/bip-
> > 0152.mediawiki#short-transaction-id-calculation
> > 
> > On Thu, May 26, 2022 at 3:59 AM <eric@voskuil.org
> > mailto:eric@voskuil.org > wrote:
> > 
> > Given that packages have no header, the package requires
> > identity in a
> > BIP152 scheme. For example 'header' and 'blockhash' fields
> > can be replaced
> > with a Merkle root (e.g. "identity" field) for the package,
> > uniquely
> > identifying the partially-ordered set of txs. And use of
> > 'getdata' (to
> > obtain a package by hash) can be eliminated (not a use case).
> > 
> > e
> > 
> > > -----Original Message-----
> > > From: eric@voskuil.org mailto:eric@voskuil.org
> > <eric@voskuil.org mailto:eric@voskuil.org >
> > > Sent: Wednesday, May 25, 2022 1:52 PM
> > > To: 'Anthony Towns' <aj@erisian.com.au
> > mailto:aj@erisian.com.au >; 'Bitcoin Protocol Discussion'
> > > <bitcoin-dev@lists.linuxfoundation.org <mailto:bitcoin-
> > dev@lists.linuxfoundation.org> >; 'Gloria Zhao'
> > > <gloriajzhao@gmail.com mailto:gloriajzhao@gmail.com >
> > > Subject: RE: [bitcoin-dev] Package Relay Proposal
> > >
> > > > From: bitcoin-dev <bitcoin-dev-
> > bounces@lists.linuxfoundation.org <mailto:bitcoin-dev-
> > bounces@lists.linuxfoundation.org> > On
> > > Behalf
> > > > Of Anthony Towns via bitcoin-dev
> > > > Sent: Wednesday, May 25, 2022 11:56 AM
> > >
> > > > So the other thing is what happens if the peer
> > announcing packages to us
> > > is
> > > > dishonest?
> > > >
> > > > They announce pkg X, say X has parents A B C and the fee
> > rate is
> > garbage.
> > > But
> > > > actually X has parent D and the fee rate is excellent. Do
> > we request the
> > > > package from another peer, or every peer, to double
> > check? Otherwise
> > > we're
> > > > allowing the first peer we ask about a package to censor
> > that tx from
> > us?
> > > >
> > > > I think the fix for that is just to provide the fee and weight
> > when
> > > announcing
> > > > the package rather than only being asked for its info?
> > Then if one peer
> > > makes
> > > > it sound like a good deal you ask for the parent txids from
> > them,
> > dedupe,
> > > > request, and verify they were honest about the parents.
> > >
> > > Single tx broadcasts do not carry an advertised fee rate,
> > however the'
> > > feefilter' message (BIP133) provides this distinction. This
> > should be
> > > interpreted as applicable to packages. Given this message
> > there is no
> > reason
> > > to send a (potentially bogus) fee rate with every package. It
> > can only be
> > > validated by obtaining the full set of txs, and the only
> > recourse is
> > > dropping (etc.) the peer, as is the case with single txs.
> > Relying on the
> > > existing message is simpler, more consistent, and more
> > efficient.
> > >
> > > > >> Is it plausible to add the graph in?
> > > >
> > > > Likewise, I think you'd have to have the graph info from
> > many nodes if
> > > you're
> > > > going to make decisions based on it and don't want
> > hostile peers to be
> > > able to
> > > > trick you into ignoring txs.
> > > >
> > > > Other idea: what if you encode the parent txs as a short
> > hash of the
> > wtxid
> > > > (something like bip152 short ids? perhaps seeded per
> > peer so collisions
> > > will
> > > > be different per peer?) and include that in the inv
> > announcement? Would
> > > > that work to avoid a round trip almost all of the time,
> > while still
> > giving
> > > you
> > > > enough info to save bw by deduping parents?
> > >
> > > As I suggested earlier, a package is fundamentally a
> > compact block (or
> > > block) announcement without the header. Compact block
> > (BIP152)
> > > announcement
> > > is already well-defined and widely implemented. A node
> > should never be
> > > required to retain an orphan, and BIP152 ensures this is not
> > required.
> > >
> > > Once a validated set of txs within the package has been
> > obtained with
> > > sufficient fee, a fee-optimal node would accept the largest
> > subgraph of
> > the
> > > package that conforms to fee constraints and drop any
> > peer that provides a
> > > package for which the full graph does not.
> > >
> > > Let us not reinvent the wheel and/or introduce accidental
> > complexity. I
> > see
> > > no reason why packaging is not simply BIP152 without the
> > 'header' field,
> > an
> > > updated protocol version, and the following sort of changes
> > to names:
> > >
> > > sendpkg
> > > MSG_CMPCT_PKG
> > > cmpctpkg
> > > getpkgtxn
> > > pkgtxn
> > >
> > > > > For a maximum 25 transactions,
> > > > >2324/2 = 276, seems like 36 bytes for a child-with-
> > parents package.
> > > >
> > > > If you're doing short ids that's maybe 254B=100B
> > already, then the
> > above
> > > is
> > > > up to 36% overhead, I guess. Might be worth thinking
> > more about, but
> > > maybe
> > > > more interesting with ancestors than just parents.
> > > >
> > > > >Also side note, since there are no size/count params,
> > >
> > > Size is restricted in the same manner as block and
> > transaction broadcasts,
> > > by consensus. If the fee rate is sufficient there would be no
> > reason to
> > > preclude any valid size up to what can be mined in one
> > block (packaging
> > > across blocks is not economically rational under the
> > assumption that one
> > > miner cannot expect to mine multiple blocks in a row).
> > Count is
> > incorporated
> > > into BIP152 as 'shortids_length'.
> > >
> > > > > wondering if we
> > > > >should just have "version" in "sendpackages" be a bit
> > field instead of
> > > > >sending a message for each version. 32 versions should
> > be enough right?
> > >
> > > Adding versioning to individual protocols is just a reflection
> > of the
> > > insufficiency of the initial protocol versioning design, and
> > that of the
> > > various ad-hoc changes to it (including yet another
> > approach in this
> > > proposal) that have been introduced to compensate for it,
> > though I'll
> > > address this in an independent post at some point.
> > >
> > > Best,
> > > e
> > >
> > > > Maybe but a couple of messages per connection doesn't
> > really seem worth
> > > > arguing about?
> > > >
> > > > Cheers,
> > > > aj
> > > >
> > > >
> > > > --
> > > > Sent from my phone.
> > > >
> > _______________________________________________
> > > > bitcoin-dev mailing list
> > > > bitcoin-dev@lists.linuxfoundation.org <mailto:bitcoin-
> > dev@lists.linuxfoundation.org>
> > > >
> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> > 
> > _______________________________________________
> > bitcoin-dev mailing list
> > bitcoin-dev@lists.linuxfoundation.org <mailto:bitcoin-
> > dev@lists.linuxfoundation.org>
> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> 
> 
> 
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[bitcoin-dev] Packaged Transaction Relay

[eric]

Hi Suhas/Gloria,

Good questions. I've started a new thread because it became something else...

Various ideas about packaging seem to be focused on the idea of an atomic message that is gossiped around the network like a transaction or block. From my perspective that seems to create a set of problems without good solutions, and it is not a proper analogy to those atomic structures. It may be worth taking the time to step back and take a close look at the underlying objective.

The sole objective, as expressed in the OP proposal, is to:

"Propagate transactions that are incentive-compatible to mine, even if they don't meet minimum feerate alone."

Effectively producing this outcome with an atomic packaging approach while at the same time maintaining network invariants seems unlikely, if not impossible.

Fees:

A node knows what fee rate a peer will accept, and announces individual txs that satisfy peer.feerate. Similarly a node knows its own feerate, and SHOULD drop any peer that announces txs that do not satisfy node.feerate.

Orphans:

A node MAY drop a peer that announces txs that the node sees as orphans against its DAG. It SHOULD drop the orphan tx and MAY request missing ancestors. Presumably after some amount of time connected to peer, node does not expect to see any more orphans from that peer, so these choices could evolve with the channel. However, the design that can only consider each tx in isolation will continue to cause orphan announcements on the channel. A below peer.feerate tx does not get announced to peer, and later a descendant high peer.feerate does get announced to the peer - as an orphan.

BIP133 (feefilter):

"There could be a small number of edge cases where a node's mempool min fee is actually less than the filter value a peer is aware of and transactions with fee rates between these values will now be newly inhibited."

https://github.com/bitcoin/bips/blob/master/bip-0133.mediawiki

Whether the problem is "small" or not depends on the disparity between node fee rates, which is not a matter of protocol. This is an existing problem that can and should be dealt with in packaging, as part of the above objective. 

Packaged Transaction Relay:

One might instead think of packaging as a per-connection function, operating over its transaction (input->output) DAG and the feerate of its own node and that of the peer. Logically a "package" is nothing more than a set of transactions (optimized by announcement). Only a node can effectively determine the packaging required by each of its peers, since only the node is aware of peer.feerate.

The only way to avoid dead-ending packages (including individual transactions, as is the objective) is for a node to package txs for each peer. The origination of any package is then just a wallet peer doing what a node does - packaging transactions that satisfy peer.feerate (i.e. that of its node).

Current transaction relay (txB->txA):
===============================
Node0
txA.feerate > node.feerate, and not orphaned (accept txA)
txA.feerate > peer1.feerate (announce txA to peer1)
txA.feerate < peer2.feerate (do not announce txA to peer2)
-----
txB.feerate > node.feerate (accept txB)
txB.feerate > peer1.feerate (announce txB to peer1)
txB.feerate > peer2.feerate (announce txB to peer2)

Node1
Sees/accepts txA and txB.

Node2
Never sees txA, sees/rejects txB (as an orphan).

Packaged transaction relay (txB->txA):
===============================
Node0
txA.feerate > node.feerate, and not orphaned (accept txA)
txA.feerate > peer1.feerate (announce txA to peer1)
txA.feerate < peer2.feerate (do not announce txA to peer2)
-----
txB.feerate > node1.feerate (accept txB)
txB.feerate > peer1.feerate (announce txB to peer1)
txB.feerate > peer2.feerate (do not announce txB to peer2) <== avoid predictable orphan
txA.feerate + txB.feerate > peer2.feerate (announce pkg(A, B) to peer2) <= create minimal package

Node1
Sees/accepts txA and txB.

Node2
pkg(A, B) > node2.feerate (accept txA, txB)
txA.feerate > peer3.feerate (announce txA to peer3)
txB.feerate > peer3.feerate (announce txB to peer3)

Sees/accepts pkg(A, B).

Node3
Sees/accepts txA and txB. <= avoided unnecessary packaging

Summary:

In this design, any node that receives an announcement for a pkg (or tx) later determined to be less than node.feerate SHOULD drop the announcing peer. Unlike with existing tx relay, a node can become "current" and subsequently see few if any tx or pkg orphans, and MAY at some point decide to drop any peer that announces one. Notice that packages are created dynamically, and any package that doesn't need to be grouped gets trimmed down to individual transactions. Furthermore any tx that is "stuck" can be freed by simply sending another tx. The nodes at which the tx has become stuck will just package it up and relay it to peers. In other words, there is no impact on wallet implementation apart from raising the aggregate fee using a descendant transaction.

This is barely a protocol change - it's primarily implementation. All that should be required is an additional INV element type, such as MSG_TX_PACKAGE.

Additional constraints:

* All elements of MSG_TX_PACKAGE in one INV message MUST to be of the same package.
* A package MUST must define a set that can be mined into one block (size/sigops constraint).
* A package SHOULD not contain confirmed txs (a race may cause this).
* A package MUST minimally satisfy peer.feerate.
* A partial tx order, as in the manner of the block.txs ordering, MUST be imposed.
* A node SHOULD drop a peer that sends a package (or tx) below node.feerate.
* A node MAY drop a peer that sends a non-minimal package according to node.feerate.

The partial ordering of block.txs introduces an ordering constraint that precludes full parallelism in validating input attachment. This is an implementation artifact that made its way into consensus. However in the case of packaging, the set of txs is not presumed to be valid under the proof of work DoS guard. As such constraints should minimize the work/traffic required to invalidate the message. The partial order constraint ensures that the DAG can be built incrementally, dropping the attempt (and peer as desired) as soon as the first orphan is discovered. As a result the network traffic and work required is not materially different than with tx relay, with two exceptions.

These are the two central aspects of this approach (Avoiding Predictable Orphans and Creating Minimal Packages). These are graph search algorithms, some basic computer science. Minimality requires only that the package does not introduce txs that are not necessary to reach the peer.feerate (as these can always be packaged separately). It does not require that nodes all generate the same packages. It does not require negotiation, package identity, cryptography, or hashing. As a graph search it should be O(n) where n is the unconfirmed ancestry of the package, but should typically be much lower, if not a single step.

Sufficiently-low-fee nodes will see only single txs. Moderate-fee nodes may cause partial breakup of packages. Sufficiently high fee nodes will cause peers (having received and completed the acceptance of a tx/pkg with pkg.feerate < peer.feerate) to navigate from each tx/package external input until reaching txs above peer.feerate, or confirmed (both of which the peer is presumed to already have). If the pkg.feerate is sufficiently high to connect all external inputs to the intervening txs, they are added to the package and it is announced to the high fee peer. Note that the individual tx.feerate > peer.feerate is insufficient to ensure that the peer should have the tx, as there may be ancestor txs that do not, and for which the tx was insufficient to cause them to be packaged. So a non-caching algorithm must be able to chase each package external input to a confirmed tx (or cache the unconfirmed ancestry fee rate at each tx). Note that fee rates are not directly additive, both size/weight and fee are required for summation (and aggregate sigops should be considered).

This makes no assumptions about current implementations. The design would call for maintenance of a transaction (input->output) DAG with tx.feerate on each tx. This could be the unconfirmed tx graph (i.e. "memory pool") though it does not require maintenance of anything more than the parameters necessary to confirm a set of validated txs within a block. It is very reasonable to require this of any participating node. A simple version negotiation can identify a package-accepting/sending nodes.

I have thought about this for some time, but have not implemented either the graph search, source code, or BIP. Just wrote this off the top of my head. So I am sure there are some things I have incorrect or failed to consider. But I think it's worth discussing it at this point.

e

> -----Original Message-----
> From: bitcoin-dev <bitcoin-dev-bounces@lists.linuxfoundation.org> On
> Behalf Of Suhas Daftuar via bitcoin-dev
> Sent: Wednesday, June 8, 2022 8:59 AM
> To: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
> Subject: Re: [bitcoin-dev] Package Relay Proposal
> 
> Hi,
> 
> Thanks again for your work on this!
> 
> One question I have is about potential bandwidth waste in the case of nodes
> running with different policy rules.  Here's my understanding of a scenario I
> think could happen:
> 
> 1) Transaction A is both low-fee and non-standard to some nodes on the
> network.
> 2) Whenever a transaction T that spends A is relayed, new nodes will send
> INV(PKGINFO1, T) to all package-relay peers.
> 3) Nodes on the network that have implemented package relay, but do not
> accept A, will send getdata(PKGINFO1, T) and learn all of T's unconfirmed
> parents (~32 bytes * number of parents(T)).
> 4) Such nodes will reject T.  But because of transaction malleability, and to
> avoid being blinded to a transaction unnecessarily, these nodes will likely still
> send getdata(PKGINFO1, T) to every node that announces T, in case
> someone has a transaction that includes an alternate set of parent
> transactions that would pass policy checks.
> 
> Is that understanding correct?  I think a good design goal would be to not
> waste bandwidth in non-adversarial situations.  In this case, there would be
> bandwidth waste from downloading duplicate data from all your peers, just
> because the announcement doesn't commit to the set of parent wtxids that
> we'd get from the peer (and so we are unable to determine that all our peers
> would be telling us the same thing, just based on the announcement).
> 
> Some ways to mitigate this might be to: (a) include a hash (maybe even just a
> 20-byte hash -- is that enough security?) of the package wtxids (in some
> canonical ordering) along with the wtxid of the child in the initial
> announcement; (b) limit the use of v1 packages to transactions with very few
> parents (I don't know if this is reasonable for the use cases we have in mind).
> 
> Another point I wanted to bring up is about the rules around v1 package
> validation generally, and the use of a blockhash in transaction relay
> specifically.  My first observation is that it won't always be the case that a v1
> package relay node will be able to validate that a set of package transactions
> is fully sorted topologically, because there may be (non-parent) ancestors
> that are missing from the package and the best a peer can validate is
> topology within the package -- this means that a peer can validly (under this
> BIP) relay transaction packages out of the true topological sort (if all
> ancestors were included).
> 
> This makes me wonder how useful this topological rule is.  I suppose there is
> some value in preventing completely broken implementations from staying
> connected and so there is no harm in having the rule, but perhaps it would
> be helpful to add that nodes SHOULD order transactions based on topological
> sort in the complete transaction graph, so that if missing-from-package
> ancestors are already known by a peer (which is the expected case when
> using v1 package relay on transactions that have more than one generation
> of unconfirmed ancestor) then the remaining transactions are already
> properly ordered, and this is helpful even if unenforceable in general.
> 
> The other observation I wanted to make was that having transaction relay
> gated on whether two nodes agree on chain tip seems like an overly
> restrictive criteria.  I think an important design principle is that we want to
> minimize disruption from network splits -- if there are competing blocks
> found in a small window of time, it's likely that the utxo set is not materially
> different on the two chains (assuming miners are selecting from roughly the
> same sets of transactions when this happens, which is typical).  Having
> transaction relay bifurcate on the two network halves would seem to
> exacerbate the difference between the two sides of the split -- users ought
> to be agnostic about how benign splits are resolved and would likely want
> their transactions to relay across the whole network.
> 
> Additionally, use of a chain tip might impose a larger burden than is necessary
> on software that would seek to participate in transaction relay without
> implementing headers sync/validation.  I don't know what software exists on
> the network, but I imagine there are a lot of scripts out there for transaction
> submission to the public p2p network, and in thinking about modifying such a
> script to utilize package relay it seems like an unnecessary added burden to
> first learn a node's tip before trying to relay a transaction.
> 
> Could you explain again what the benefit of including the blockhash is?  It
> seems like it is just so that a node could prioritize transaction relay from
> peers with the same chain tip to maximize the likelihood of transaction
> acceptance, but in the common case this seems like a pretty negligible
> concern, and in the case of a chain fork that persists for many minutes it
> seems better to me that we not partition the network into package-relay
> regimes and just risk a little extra bandwidth in one direction or the other.  If
> we solve the problem I brought up at the beginning (of de-duplicating
> package data across peers with a package-wtxid-commitment in the
> announcement), I think this is just some wasted pkginfo bandwidth on a
> single-link, and not across links (as we could cache validation failure for a
> package-hash to avoid re-requesting duplicate pkginfo1 messages).
> 
> Best,
> Suhas
> 
> 
> On Tue, Jun 7, 2022 at 1:57 PM Gloria Zhao via bitcoin-dev <bitcoin-
> dev@lists.linuxfoundation.org <mailto:bitcoin-
> dev@lists.linuxfoundation.org> > wrote:
> 
> 
> 	Hi Eric, aj, all,
> 
> 	Sorry for the delayed response. @aj I'm including some paraphrased
> points from our offline discussion (thanks).
> 
> 
> 	> Other idea: what if you encode the parent txs as a short hash of the
> wtxid (something like bip152 short ids? perhaps seeded per peer so collisions
> will be different per peer?) and include that in the inv announcement?
> Would that work to avoid a round trip almost all of the time, while still giving
> you enough info to save bw by deduping parents?
> 
> 
> 	> As I suggested earlier, a package is fundamentally a compact block
> (or
> 	> block) announcement without the header. Compact block (BIP152)
> announcement
> 	> is already well-defined and widely implemented...
> 
> 
> 
> 	> Let us not reinvent the wheel and/or introduce accidental
> complexity. I see
> 	> no reason why packaging is not simply BIP152 without the 'header'
> field, an
> 	> updated protocol version, and the following sort of changes to
> names
> 
> 	Interestingly, "why not use BIP 152 shortids to save bandwidth?" is
> by far the most common suggestion I hear (including offline feedback).
> Here's a full explanation:
> 
> 	BIP 152 shortens transaction hashes (32 bytes) to shortids (6 bytes)
> to save a significant amount of network bandwidth, which is extremely
> important in block relay. However, this comes at the expense of
> computational complexity. There is no way to directly calculate a transaction
> hash from a shortid; upon receipt of a compact block, a node is expected to
> calculate the shortids of every unconfirmed transaction it knows about to
> find the matches (BIP 152: [1], Bitcoin Core: [2]). This is expensive but
> appropriate for block relay, since the block must have a valid Proof of Work
> and new blocks only come every ~10 minutes. On the other hand, if we
> require nodes to calculate shortids for every transaction in their mempools
> every time they receive a package, we are creating a DoS vector.
> Unconfirmed transactions don't need PoW and, to have a live transaction
> relay network, we should expect nodes to handle transactions at a high-ish
> rate (i.e. at least 1000s of times more transactions than blocks). We can't pre-
> calculate or cache shortids for mempool transactions, since the SipHash key
> depends on the block hash and a per-connection salt.
> 
> 	Additionally, shortid calculation is not designed to prevent intentional
> individual collisions. If we were to use these shortids to deduplicate
> transactions we've supposedly already seen, we may have a censorship
> vector. Again, these tradeoffs make sense for compact block relay (see
> shortid section in BIP 152 [3]), but not package relay.
> 
> 	TLDR: DoSy if we calculate shortids on every package and censorship
> vector if we use shortids for deduplication.
> 
> 	> Given this message there is no reason
> 	> to send a (potentially bogus) fee rate with every package. It can
> only be
> 	> validated by obtaining the full set of txs, and the only recourse is
> 	> dropping (etc.) the peer, as is the case with single txs.
> 
> 
> 	Yeah, I agree with this. Combined with the previous discussion with
> aj (i.e. we can't accurately communicate the incentive compatibility of a
> package without sending the full graph, and this whole dance is to avoid
> downloading a few low-fee transactions in uncommon edge cases), I've
> realized I should remove the fee + weight information from pkginfo. Yay for
> less complexity!
> 
> 
> 	Also, this might be pedantic, but I said something incorrect earlier
> and would like to correct myself:
> 
> 	>> In theory, yes, but maybe it was announced earlier (while our
> node was down?) or had dropped from our mempool or similar, either way
> we don't have those txs yet.
> 
> 	I said "It's fine if they have Erlay, since a sender would know in
> advance that B is missing and announce it as a package." But this isn't true
> since we're only using reconciliation in place of flooding to announce
> transactions as they arrive, not for rebroadcast, and we're not doing full
> mempool set reconciliation. In any case, making sure a node receives the
> transactions announced when it was offline is not something we guarantee,
> not an intended use case for package relay, and not worsened by this.
> 
> 	Thanks for your feedback!
> 
> 	Best,
> 
> 	Gloria
> 
> 	[1]: https://github.com/bitcoin/bips/blob/master/bip-
> 0152.mediawiki#cmpctblock
> 	[2]:
> https://github.com/bitcoin/bitcoin/blob/master/src/blockencodings.cpp#L49
> 	[3]: https://github.com/bitcoin/bips/blob/master/bip-
> 0152.mediawiki#short-transaction-id-calculation
> 
> 	On Thu, May 26, 2022 at 3:59 AM <eric@voskuil.org
> <mailto:eric@voskuil.org> > wrote:
> 
> 
> 		Given that packages have no header, the package requires
> identity in a
> 		BIP152 scheme. For example 'header' and 'blockhash' fields
> can be replaced
> 		with a Merkle root (e.g. "identity" field) for the package,
> uniquely
> 		identifying the partially-ordered set of txs. And use of
> 'getdata' (to
> 		obtain a package by hash) can be eliminated (not a use case).
> 
> 		e
> 
> 		> -----Original Message-----
> 		> From: eric@voskuil.org <mailto:eric@voskuil.org>
> <eric@voskuil.org <mailto:eric@voskuil.org> >
> 		> Sent: Wednesday, May 25, 2022 1:52 PM
> 		> To: 'Anthony Towns' <aj@erisian.com.au
> <mailto:aj@erisian.com.au> >; 'Bitcoin Protocol Discussion'
> 		> <bitcoin-dev@lists.linuxfoundation.org <mailto:bitcoin-
> dev@lists.linuxfoundation.org> >; 'Gloria Zhao'
> 		> <gloriajzhao@gmail.com <mailto:gloriajzhao@gmail.com> >
> 		> Subject: RE: [bitcoin-dev] Package Relay Proposal
> 		>
> 		> > From: bitcoin-dev <bitcoin-dev-
> bounces@lists.linuxfoundation.org <mailto:bitcoin-dev-
> bounces@lists.linuxfoundation.org> > On
> 		> Behalf
> 		> > Of Anthony Towns via bitcoin-dev
> 		> > Sent: Wednesday, May 25, 2022 11:56 AM
> 		>
> 		> > So the other thing is what happens if the peer
> announcing packages to us
> 		> is
> 		> > dishonest?
> 		> >
> 		> > They announce pkg X, say X has parents A B C and the fee
> rate is
> 		garbage.
> 		> But
> 		> > actually X has parent D and the fee rate is excellent. Do
> we request the
> 		> > package from another peer, or every peer, to double
> check? Otherwise
> 		> we're
> 		> > allowing the first peer we ask about a package to censor
> that tx from
> 		us?
> 		> >
> 		> > I think the fix for that is just to provide the fee and weight
> when
> 		> announcing
> 		> > the package rather than only being asked for its info?
> Then if one peer
> 		> makes
> 		> > it sound like a good deal you ask for the parent txids from
> them,
> 		dedupe,
> 		> > request, and verify they were honest about the parents.
> 		>
> 		> Single tx broadcasts do not carry an advertised fee rate,
> however the'
> 		> feefilter' message (BIP133) provides this distinction. This
> should be
> 		> interpreted as applicable to packages. Given this message
> there is no
> 		reason
> 		> to send a (potentially bogus) fee rate with every package. It
> can only be
> 		> validated by obtaining the full set of txs, and the only
> recourse is
> 		> dropping (etc.) the peer, as is the case with single txs.
> Relying on the
> 		> existing message is simpler, more consistent, and more
> efficient.
> 		>
> 		> > >> Is it plausible to add the graph in?
> 		> >
> 		> > Likewise, I think you'd have to have the graph info from
> many nodes if
> 		> you're
> 		> > going to make decisions based on it and don't want
> hostile peers to be
> 		> able to
> 		> > trick you into ignoring txs.
> 		> >
> 		> > Other idea: what if you encode the parent txs as a short
> hash of the
> 		wtxid
> 		> > (something like bip152 short ids? perhaps seeded per
> peer so collisions
> 		> will
> 		> > be different per peer?) and include that in the inv
> announcement? Would
> 		> > that work to avoid a round trip almost all of the time,
> while still
> 		giving
> 		> you
> 		> > enough info to save bw by deduping parents?
> 		>
> 		> As I suggested earlier, a package is fundamentally a
> compact block (or
> 		> block) announcement without the header. Compact block
> (BIP152)
> 		> announcement
> 		> is already well-defined and widely implemented. A node
> should never be
> 		> required to retain an orphan, and BIP152 ensures this is not
> required.
> 		>
> 		> Once a validated set of txs within the package has been
> obtained with
> 		> sufficient fee, a fee-optimal node would accept the largest
> subgraph of
> 		the
> 		> package that conforms to fee constraints and drop any
> peer that provides a
> 		> package for which the full graph does not.
> 		>
> 		> Let us not reinvent the wheel and/or introduce accidental
> complexity. I
> 		see
> 		> no reason why packaging is not simply BIP152 without the
> 'header' field,
> 		an
> 		> updated protocol version, and the following sort of changes
> to names:
> 		>
> 		> sendpkg
> 		> MSG_CMPCT_PKG
> 		> cmpctpkg
> 		> getpkgtxn
> 		> pkgtxn
> 		>
> 		> > > For a maximum 25 transactions,
> 		> > >23*24/2 = 276, seems like 36 bytes for a child-with-
> parents package.
> 		> >
> 		> > If you're doing short ids that's maybe 25*4B=100B
> already, then the
> 		above
> 		> is
> 		> > up to 36% overhead, I guess. Might be worth thinking
> more about, but
> 		> maybe
> 		> > more interesting with ancestors than just parents.
> 		> >
> 		> > >Also side note, since there are no size/count params,
> 		>
> 		> Size is restricted in the same manner as block and
> transaction broadcasts,
> 		> by consensus. If the fee rate is sufficient there would be no
> reason to
> 		> preclude any valid size up to what can be mined in one
> block (packaging
> 		> across blocks is not economically rational under the
> assumption that one
> 		> miner cannot expect to mine multiple blocks in a row).
> Count is
> 		incorporated
> 		> into BIP152 as 'shortids_length'.
> 		>
> 		> > > wondering if we
> 		> > >should just have "version" in "sendpackages" be a bit
> field instead of
> 		> > >sending a message for each version. 32 versions should
> be enough right?
> 		>
> 		> Adding versioning to individual protocols is just a reflection
> of the
> 		> insufficiency of the initial protocol versioning design, and
> that of the
> 		> various ad-hoc changes to it (including yet another
> approach in this
> 		> proposal) that have been introduced to compensate for it,
> though I'll
> 		> address this in an independent post at some point.
> 		>
> 		> Best,
> 		> e
> 		>
> 		> > Maybe but a couple of messages per connection doesn't
> really seem worth
> 		> > arguing about?
> 		> >
> 		> > Cheers,
> 		> > aj
> 		> >
> 		> >
> 		> > --
> 		> > Sent from my phone.
> 		> >
> _______________________________________________
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> 		> >
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> 
> 
> 
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