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From: "Russell O'Connor" <roconnor@blockstream.io>
To: Peter Todd <pete@petertodd.org>
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Revisiting BIP 125 RBF policy.
Date: Mon, 12 Feb 2018 18:19:40 -0500	[thread overview]
Message-ID: <CAMZUoKnFBVFhaq61wKu_CcZgRKc5aoeTa-wq9h2CXH0WWHd3NQ@mail.gmail.com> (raw)
In-Reply-To: <20180212225828.GB8551@fedora-23-dvm>

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On Mon, Feb 12, 2018 at 5:58 PM, Peter Todd <pete@petertodd.org> wrote:

>
> I don't actually see where the problem is here. First of all, suppose we
> have a
> transaction T_a that already pays Alice with a feerate sufficiently high
> that
> we expect it to get mined in the near future. If we want to pay Bob, we
> can do
> that by simply creating a double-spend of T_a that pays both Bob and Alice,
> T_{ab}. BIP125 only requires that double-spend to have an absolute fee
> higher
> than the minimum relay feerate * size of the transaction.
>

The problem is that rule 3 of BIP 125 requires you pay a fee that is higher
than the the fee of T_a *plus* the fee of the sweep-transaction that the
Alice has added as a unconfirmed child transaction to T_a because
double-spending to pay Alice and Bob invalidates Alice's
sweep-transaction.  Alice's sweep-transaction is very large, and hence pays
a large absolute fee even though her fee-rate is very low.  We do not have
any control over its value, hence Alice has "pinned" our RBF transaction.

> 3'. The replacement transaction pays a fee rate of at least the effective
> > fee rate of any chain of transactions from the set of original
> transactions
> > that begins with the root of the original transaction set.
>
> I think what you mean here should be the effective fee rate of the maximum
> feerate package that can be built from the set of transactions that begins
> with
> the candidate replacement. But actually calculating this is I believe
> non-trivial, which is why I didn't implement it this way when RBF was first
> implemented.
>

Yes, that is what I mean.  My proposal was off-the-mark.

Surely CPFP is already computing the package-fee rates of mempool
transactions.  That is the value we need to compute.

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  reply	other threads:[~2018-02-12 23:20 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-12 15:52 [bitcoin-dev] Revisiting BIP 125 RBF policy Russell O'Connor
2018-02-12 17:30 ` rhavar
2018-02-12 22:58 ` Peter Todd
2018-02-12 23:19   ` Russell O'Connor [this message]
2018-02-12 23:42     ` Peter Todd
2018-02-12 23:46       ` Russell O'Connor
2018-02-14 14:08       ` Russell O'Connor
2018-02-14 14:16         ` Greg Sanders
2018-02-27 16:25       ` Russell O'Connor
2018-03-01 15:11         ` Peter Todd
2018-03-08 15:39           ` Russell O'Connor
2018-03-08 18:34             ` Peter Todd
2018-03-08 20:07               ` Russell O'Connor
2018-03-09 18:28                 ` Peter Todd
2018-03-09 18:40                   ` rhavar
2018-02-12 23:23   ` rhavar
2018-02-13 18:40     ` Peter Todd
2018-02-14  2:07       ` rhavar

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