From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id BA8ECE91 for ; Sat, 29 Aug 2015 17:52:07 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-ig0-f169.google.com (mail-ig0-f169.google.com [209.85.213.169]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id C7B1710C for ; Sat, 29 Aug 2015 17:52:06 +0000 (UTC) Received: by igcse8 with SMTP id se8so42059130igc.1 for ; Sat, 29 Aug 2015 10:52:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-type; bh=ekalFp0fADHcVH5ZYnhjI6gsLUndowcWdcjwPk/sR3w=; b=E/YAIl+1khA/XDw3+3vnHLfuHk/Ny5LRhIOxPWebNSslWT5gMl3CXCp1wQ3LNKkQqE 1ommcKvmS9uV52/9okVnNgBt0wCsWaCC3ip9WW1AyKkjf5ySaWiLZrzSlkpSskhuMJuL VEZflno9njZFdoLl5Wa09gzc9uWB07ztjHx1Lld41FgZ9OcrmjHC0IBOBjtJT1YHXNww 4dz8uhLJYBAfjGoQVnmRMIbwqe3T5+TRb8Kb3PheKb2ZxkZgjkQygHSex7Odj4PPZKdy IgEeAW0uRj/LGD0b9e1hpN66N0gNAF/5ONMrTk6CTqCvSFjXGm7pscMdY0dYkfu92fuB IeiQ== X-Received: by 10.50.62.46 with SMTP id v14mr8204630igr.79.1440870726300; Sat, 29 Aug 2015 10:52:06 -0700 (PDT) MIME-Version: 1.0 References: <2081355.cHxjDEpgpW@crushinator> In-Reply-To: From: Eric Lombrozo Date: Sat, 29 Aug 2015 17:51:56 +0000 Message-ID: To: Btc Drak , Mark Friedenbach Content-Type: multipart/alternative; boundary=047d7bd77122cefb67051e76db8f X-Spam-Status: No, score=-2.7 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,HTML_MESSAGE,RCVD_IN_DNSWL_LOW autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Cc: Bitcoin Dev Subject: Re: [bitcoin-dev] Consensus based block size retargeting algorithm (draft) X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Development Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 29 Aug 2015 17:52:07 -0000 --047d7bd77122cefb67051e76db8f Content-Type: text/plain; charset=UTF-8 In principle I am sympathetic to dynamic block size proposals...but in practice it seems we're barking up the wrong tree. Without mechanisms for incentivizing validators...and checks and balances between the interests of regular users (who want to reduce fees and confirmation time), miners (who want to balance hashing and propagation time costs with revenue), and validator nodes (who currrently lack any direct incentives), I think we're talking about significant protocol complications with potential benefits that are hard to model at best. On Sat, Aug 29, 2015, 3:16 AM Btc Drak via bitcoin-dev < bitcoin-dev@lists.linuxfoundation.org> wrote: > On Sat, Aug 29, 2015 at 1:29 AM, Mark Friedenbach via bitcoin-dev > wrote: > > Ah, then my mistake. It seemed so similar to an idea that was proposed > > before on this mailing list: > > > > > http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-May/008033.html > > > > that my mind just filled in the gaps. I concur -- having miners -- or any > > group -- vote on block size is not an intrinsically good thing. The the > > original proposal due to Greg Maxwell et al was not a mechanism for > "voting" > > but rather a feedback control that made the maximum block size that which > > generated the most fees. > > Mark and Jorge, > > I am very glad you have brought up this particular objection because > it's something I thought about but was unclear if it was an opinion > that would be shared by others. I chose to omit it from the proposal > to see if it would come up during peer review. > > I feel that giving miners a blank cheque to increase blocksize, by any > means, goes against a key design of bitcoin's security model. Full > nodes keep miners honest by ensuring by validating their blocks. Under > any voting-only scheme there is no way for full nodes to keep miners > in cheque because miner have free reign to increase the blocksize. > > This problem can be solved by introducing a hard cap on blocksize. By > introducing an upper limit miners now have the freedom to increase > blocksize but only within defined parameters. Remember my proposal > allows blocksize to increase and decrease in such a way that miners > must collectively agree if they want the size to increase. > > I believe the idea of a hard upper limit has become rather politicised > but is essential to the security model of bitcoin. > > With respect to the flexicap idea where miners can create a larger > block by paying extra difficulty, I believe that proposal has a > critical flaw because, as Gavin pointed out, it makes it very > expensive (and risky) to include a few extra transactions. I believe > it suffers from tragedy of the commons because there is no incentive > for the mining community to reach consensus. Each and every block is > going to be a gamble, "should we include a few extra transactions at > the risk of losing the block?". Under my proposal miners can > collectively agree to change the blocksize. Let's say they want a 10% > increase, they can collude together to make that increase and once > reached, it remains until they want to change it again. Yet, the upper > hard limit keeps the ultimate control of the maximum block size > squarely in the hands of full nodes. > > Whilst the exact number may be up for discussion, I would propose an > initial upper limit of 8MB, so under my proposal the blocksize would > be flexible between 1MB and 8MB. > > An alternative methodology to voting in the coinbase would be to > change the vote to be the blocksize itself > > 1. miners pay extra difficulty to create a larger block. > 2. every 2016 blocks the average or median of the last 2016 blocks is > calculated and becomes the new maximum blocksize limit. > > This would retain incentive to collude to increase blocksize, as well > as the property of costing to increase while being free to propose > decrease. > > It would still require an upper blocksize limit in order for full > nodes to retain control. Without an upper limit, any proposal is going > to break the security model as full nodes give up some oversight > control over miners. > > Another way of looking at these ideas is we're raising blocksize hard > limit (to 8MB or whatever is decided), but making a soft of "softer" > or inner limit part of consensus. Such a concept is not really > departing from the current idea of a soft limit except to make it > consensus enforced. Obviously it's not identical, but I think you can > see the similarities. > > Does that make sense? > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > --047d7bd77122cefb67051e76db8f Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

In principle I am sympathetic to dynamic block size proposal= s...but in practice it seems we're barking up the wrong tree. Without m= echanisms for incentivizing validators...and checks and balances between th= e interests of regular users (who want to reduce fees and confirmation time= ), miners (who want to balance hashing and propagation time costs with reve= nue), and validator nodes (who currrently lack any direct incentives), I th= ink we're talking about significant protocol complications with potenti= al benefits that are hard to model at best.


On Sat, Aug 29, 2015, 3:16 = AM=C2=A0Btc Drak via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:
=
On Sat, Aug 29, 2015 at 1:29 AM, Mark = Friedenbach via bitcoin-dev
<bitcoin-dev@lists.linuxfoundation.org> wrote:
> Ah, then my mistake. It seemed so similar to an idea that was proposed=
> before on this mailing list:
>
> http://lists.linuxfo= undation.org/pipermail/bitcoin-dev/2015-May/008033.html
>
> that my mind just filled in the gaps. I concur -- having miners -- or = any
> group -- vote on block size is not an intrinsically good thing. The th= e
> original proposal due to Greg Maxwell et al was not a mechanism for &q= uot;voting"
> but rather a feedback control that made the maximum block size that wh= ich
> generated the most fees.

Mark and Jorge,

I am very glad you have brought up this particular objection because
it's something I thought about but was unclear if it was an opinion
that would be shared by others. I chose to omit it from the proposal
to see if it would come up during peer review.

I feel that giving miners a blank cheque to increase blocksize, by any
means, goes against a key design of bitcoin's security model. Full
nodes keep miners honest by ensuring by validating their blocks. Under
any voting-only scheme there is no way for full nodes to keep miners
in cheque because miner have free reign to increase the blocksize.

This problem can be solved by introducing a hard cap on blocksize. By
introducing an upper limit miners now have the freedom to increase
blocksize but only within defined parameters.=C2=A0 Remember my proposal allows blocksize to increase and decrease in such a way that miners
must collectively agree if they want the size to increase.

I believe the idea of a hard upper limit has become rather politicised
but is essential to the security model of bitcoin.

With respect to the flexicap idea where miners can create a larger
block by paying extra difficulty, I believe that proposal has a
critical flaw because, as Gavin pointed out, it makes it very
expensive (and risky) to include a few extra transactions. I believe
it suffers from tragedy of the commons because there is no incentive
for the mining community to reach consensus. Each and every block is
going to be a gamble, "should we include a few extra transactions at the risk of losing the block?". Under my proposal miners can
collectively agree to change the blocksize. Let's say they want a 10% increase, they can collude together to make that increase and once
reached, it remains until they want to change it again. Yet, the upper
hard limit keeps the ultimate control of the maximum block size
squarely in the hands of full nodes.

Whilst the exact number may be up for discussion, I would propose an
initial upper limit of 8MB, so under my proposal the blocksize would
be flexible between 1MB and 8MB.

An alternative methodology to voting in the coinbase would be to
change the vote to be the blocksize itself

1. miners pay extra difficulty to create a larger block.
2. every 2016 blocks the average or median of the last 2016 blocks is
calculated and becomes the new maximum blocksize limit.

This would retain incentive to collude to increase blocksize, as well
as the property of costing to increase while being free to propose
decrease.

It would still require an upper blocksize limit in order for full
nodes to retain control. Without an upper limit, any proposal is going
to break the security model as full nodes give up some oversight
control over miners.

Another way of looking at these ideas is we're raising blocksize hard limit (to 8MB or whatever is decided), but making a soft of "softer&qu= ot;
or inner limit part of consensus. Such a concept is not really
departing from the current idea of a soft limit except to make it
consensus enforced. Obviously it's not identical, but I think you can see the similarities.

Does that make sense?
_______________________________________________
bitcoin-dev mailing list
= bitcoin-dev@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mail= man/listinfo/bitcoin-dev
--047d7bd77122cefb67051e76db8f--