Return-Path: <roy@gnomon.org.uk> Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id B44B0BCD for <bitcoin-dev@lists.linuxfoundation.org>; Wed, 24 Jun 2015 17:29:00 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from darla.gnomon.org.uk (darla.gnomon.org.uk [93.93.131.22]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id F14551B7 for <bitcoin-dev@lists.linuxfoundation.org>; Wed, 24 Jun 2015 17:28:58 +0000 (UTC) Received: from darla.gnomon.org.uk (localhost.gnomon.org.uk [127.0.0.1]) by darla.gnomon.org.uk (8.14.3/8.14.3) with ESMTP id t5OHSl34064051 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Wed, 24 Jun 2015 18:28:52 +0100 (BST) (envelope-from roy@darla.gnomon.org.uk) Received: (from roy@localhost) by darla.gnomon.org.uk (8.14.3/8.14.1/Submit) id t5OHSloi064050; Wed, 24 Jun 2015 18:28:47 +0100 (BST) (envelope-from roy) Date: Wed, 24 Jun 2015 18:28:47 +0100 From: Roy Badami <roy@gnomon.org.uk> To: Raystonn <raystonn@hotmail.com> Message-ID: <20150624172847.GD3192@giles.gnomon.org.uk> References: <COL402-EAS745A879FDD8D3BAB8216D7CDAF0@phx.gbl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <COL402-EAS745A879FDD8D3BAB8216D7CDAF0@phx.gbl> User-Agent: Mutt/1.5.20 (2009-06-14) X-Spam-Status: No, score=-4.0 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_LOW, RP_MATCHES_RCVD 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@lists.linuxfoundation.org Subject: Re: [bitcoin-dev] Draft BIP : fixed-schedule block size increase X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Development Discussion <bitcoin-dev.lists.linuxfoundation.org> List-Unsubscribe: <https://lists.linuxfoundation.org/mailman/options/bitcoin-dev>, <mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=unsubscribe> List-Archive: <http://lists.linuxfoundation.org/pipermail/bitcoin-dev/> List-Post: <mailto:bitcoin-dev@lists.linuxfoundation.org> List-Help: <mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=help> List-Subscribe: <https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev>, <mailto:bitcoin-dev-request@lists.linuxfoundation.org?subject=subscribe> X-List-Received-Date: Wed, 24 Jun 2015 17:29:00 -0000 60% of the hashrate can easily agree to force a softfork which reduces the block size. As soon as the fork occurs, there is a very strong incentive for all the remaining 40% to go along with it: if they don't, they're mining worthless blocks. They can use a BIP-34 style mechanism to trigger the fork so there's negligible risk to the miners. On Wed, Jun 24, 2015 at 10:23:18AM -0700, Raystonn wrote: > <p dir=3D"ltr">You really believe they would risk getting orphaned by ski= pping the longer chain, just to attempt to reduce average block size? No, t= hat doesn't happen today. Laziness in leaving the default size is common. B= ut that is not collusion, nor an attempt to manipulate the block sizes of o= ther miners.<br> > </p> > <div class=3D"gmail_quote">On 24 Jun 2015 10:05 am, Mark Friedenbach <= mark@friedenbach.org> wrote:<br type=3D'attribution'><blockquote class= =3D"quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-le= ft:1ex"><p dir=3D"ltr">They do so by not building on larger blocks</p> > <div class=3D"elided-text">On Jun 23, 2015 9:31 PM, "Raystonn" &l= t;<a href=3D"mailto:raystonn@hotmail.com">raystonn@hotmail.com</a>&= gt; wrote:<br /><blockquote style=3D"margin:0 0 0 0.8ex;border-left:1px #cc= c solid;padding-left:1ex"><p dir=3D"ltr">No, they can lower their own block= sizes.?? But they cannot currently lower the sizes of blocks mined by othe= rs.?? That is not the same thing by any stretch of the imagination.</p> > <div class=3D"elided-text">On 23 Jun 2015 8:50 pm, Jeff Garzik <<a hre= f=3D"mailto:jgarzik@gmail.com">jgarzik@gmail.com</a>> wrote:<br = /><blockquote style=3D"margin:0 0 0 0.8ex;border-left:1px #ccc solid;paddin= g-left:1ex"><div dir=3D"ltr">Miners can collude today to lower the block si= ze limit.<div><br /></div><div>In fact, this largely happens already out of= laziness - miners often follow the "soft" default limit set by Bit= coin Core, to the point where you can chart when miners upgrade to new soft= ware:??<a href=3D"http://hashingit.com/analysis/39-the-myth-of-the-megabyte= -bitcoin-block">http://hashingit.com/analysis/39-the-myth-of-the-megabyte-b= itcoin-block</a></div><div><br /></div><div><br /></div></div><div><br /><d= iv>On Tue, Jun 23, 2015 at 8:05 PM, William Madden <span dir=3D"ltr"><<a= href=3D"mailto:will.madden@novauri.com">will.madden@novauri.com</a= >></span> wrote:<br /><blockquote style=3D"margin:0 0 0 0.8ex;border-lef= t:1px #ccc solid;padding-left:1ex">Here are refutations of the approach in = BIP-100 here:<br /> > <a href=3D"http://gtf.org/garzik/bitcoin/BIP100-blocksizechangeproposal.p= df">http://gtf.org/garzik/bitcoin/BIP100-blocksizechangeproposal.pdf</a><br= /> > <br /> > To recap BIP-100:<br /> > <br /> > 1) Hard form to remove static 1MB block size limit<br /> > 2) Add new floating block size limit set to 1MB<br /> > 3) Historical 32MB message limit remains<br /> > 4) Hard form on testnet 9/1/2015<br /> > 5) Hard form on main 1/11/2016<br /> > 6) 1MB limit changed via one-way lock in upgrade with a 12,000 block<br /> > threshold by 90% of blocks<br /> > 7) Limit increase or decrease may not exceed 2x in any one step<br /> > 8) Miners vote by encoding 'BV'+BlockSizeRequestValue into co= inbase<br /> > scriptSig, e.g. "/BV8000000/" to vote for 8M.<br /> > 9) Votes are evaluated by dropping bottom 20% and top 20%, and then the<b= r /> > most common floor (minimum) is chosen.<br /> > <br /> > 8MB limits doubling just under every 2 years makes a static value grow<br= /> > in a predictable manner.<br /> > <br /> > BIP-100 makes a static value grow (or more importantly potentially<br /> > shrink) in an unpredictable manner based on voting mechanics that are<br = /> > untested in this capacity in the bitcoin network.?? Introducing a highly<= br /> > variable and untested dynamic into an already complex system is<br /> > unnecessarily risky.<br /> > <br /> > For example, the largely arbitrary voting rules listed in 9 above can be<= br /> > gamed.?? If I control pools or have affiliates involved in pools that<br = /> > mine slightly more than 20% of blocks, I could wait until block sizes<br = /> > are 10MB, and then suddenly vote "/BV5000000/" for 20% of blocks = and<br /> > "/BV5000001/" for the remaining 10%.?? If others don't consis= tently vote<br /> > for the same "/BV#/" value, vote too consistently and have their = value<br /> > thrown out as the top 20%, I could win the resize to half capacity<br /> > "/BV5000001/" because it was the lowest repeated value not in the= bottom<br /> > 20%.<br /> > <br /> > I could use this to force an exodus to my sidechain/alt coin, or to<br /> > choke out the bitcoin network.?? A first improvement would be to only let= <br /> > BIP-100 raise the cap and not lower it, but if I can think of a<br /> > vulnerability off the top of my head, there will be others on the other<b= r /> > side of the equation that have not been thought of.?? Why bother<br /> > introducing a rube goldberg machine like voting when a simple 8mb cap<br = /> > with predictable growth gets the job done, potentially permanently?<br /> > <div><div><br /> > <br /> > On 6/23/2015 9:43 PM, odinn wrote:<br /> > > -----BEGIN PGP SIGNED MESSAGE-----<br /> > > Hash: SHA1<br /> > ><br /> > > 1) Hard fork not (necessarily) needed<br /> > > 2) See Garzik's BIP 100, better (this is not meant to say "s= uperior to<br /> > > your stuff," but rather simply to say, "Better you should wo= rk with<br /> > > Garzik to implement BIP-100, that would be good")<br /> > > 3) See points 1 and 2 above<br /> > > 4) If still reading... changes should be (as you seem to have been<b= r /> > > trying to lean towards)... lean towards gradual change; hence, chang= es<br /> > > that would flow from this BIP would be better off oriented in a<br /> > > process that dies not require the "way you have done it."<br= /> > ><br /> > > You did address that, to be fair - in your TODO, this link:<br /> > > <a href=3D"http://gavinandresen.ninja/time-to-roll-out-bigger-blocks= ">http://gavinandresen.ninja/time-to-roll-out-bigger-blocks</a><br /> > ><br /> > > contained the following link:<br /> > ><br /> > > <a href=3D"http://gavinandresen.ninja/bigger-blocks-another-way">htt= p://gavinandresen.ninja/bigger-blocks-another-way</a><br /> > ><br /> > > However, in reading that, I didn't see any meaningful statements= that<br /> > > would refute the approach in Garzik's BIP-100.<br /> > ><br /> > > Maybe a better way to say this is,<br /> > ><br /> > > Work with Jeff Garzik (which I am sure you are already having such<b= r /> > > discussions in private) as well as the list discussions,<br /> > > Move forward on BIP-100 with Garzik and other developers (not such a= <br /> > > bad plan really) and don't get caught up in XT.?? (If you feel y= ou can<br /> > > develop XT further, that is your thing but it would perhaps make you= <br /> > > lose focus, work together with other developers.)<br /> > ><br /> > > Relax into the process.?? Things will be ok.<br /> > ><br /> > > Respectfully,<br /> > ><br /> > > - -O<br /> > ><br /> > > On 06/22/2015 11:18 AM, Gavin Andresen wrote:<br /> > >> I promised to write a BIP after I'd implemented<br /> > >> increase-the-maximum-block-size code, so here it is. It also liv= es<br /> > >> at:<br /> > >> <a href=3D"https://github.com/gavinandresen/bips/blob/blocksize/= bip-8MB.mediawiki">https://github.com/gavinandresen/bips/blob/blocksize/bip= -8MB.mediawiki</a><br /> > >><br /> > >>?? I don't expect any proposal to please everybody; there are= <br /> > >> unavoidable tradeoffs to increasing the maximum block size. I<br= /> > >> prioritize implementation simplicity -- it is hard to write<br /> > >> consensus-critical code, so simpler is better.<br /> > >><br /> > >><br /> > >><br /> > >><br /> > >> BIP: ?? Title: Increase Maximum Block Size Author: Gavin Andrese= n<br /> > >> <<a href=3D"mailto:gavinandresen@gmail.com">gavinandresen= @gmail.com</a> <mailto:<a href=3D"mailto:gavinandresen@gmail.com= ">gavinandresen@gmail.com</a>>> Status:<br /> > >> Draft Type: Standards Track Created: 2015-06-22<br /> > >><br /> > >> ==Abstract==<br /> > >><br /> > >> This BIP proposes replacing the fixed one megabyte maximum block= <br /> > >> size with a maximum size that grows over time at a predictable<b= r /> > >> rate.<br /> > >><br /> > >> ==Motivation==<br /> > >><br /> > >> Transaction volume on the Bitcoin network has been growing, and<= br /> > >> will soon reach the one-megabyte-every-ten-minutes limit imposed= by<br /> > >> the one megabyte maximum block size. Increasing the maximum size= <br /> > >> reduces the impact of that limit on Bitcoin adoption and growth.= <br /> > >><br /> > >> ==Specification==<br /> > >><br /> > >> After deployment on the network (see the Deployment section for<= br /> > >> details), the maximum allowed size of a block on the main networ= k<br /> > >> shall be calculated based on the timestamp in the block header.<= br /> > >><br /> > >> The maximum size shall be 8,000,000 bytes at a timestamp of<br /> > >> 2016-01-11 00:00:00 UTC (timestamp 1452470400), and shall double= <br /> > >> every 63,072,000 seconds (two years, ignoring leap years), until= <br /> > >> 2036-01-06 00:00:00 UTC (timestamp 2083190400). The maximum size= of<br /> > >> blocks in between doublings will increase linearly based on the<= br /> > >> block's timestamp. The maximum size of blocks after 2036-01-= 06<br /> > >> 00:00:00 UTC shall be 8,192,000,000 bytes.<br /> > >><br /> > >> Expressed in pseudo-code, using integer math:<br /> > >><br /> > >> function max_block_size(block_timestamp):<br /> > >><br /> > >> time_start = 1452470400 time_double = 60*60*24*365*2 siz= e_start =<br /> > >> 8000000 if block_timestamp >= time_start+time_double*= 10 return<br /> > >> size_start * 2^10<br /> > >><br /> > >> // Piecewise-linear-between-doublings growth: time_delta =<b= r /> > >> block_timestamp - t_start doublings = time_delta / time_doub= le<br /> > >> remainder = time_delta % time_double interpolate = (size= _start *<br /> > >> 2^doublings * remainder) / time_double max_size = size_start= *<br /> > >> 2^doublings + interpolate<br /> > >><br /> > >> return max_size<br /> > >><br /> > >> ==Deployment==<br /> > >><br /> > >> Deployment shall be controlled by hash-power supermajority vote<= br /> > >> (similar to the technique used in BIP34), but the earliest possi= ble<br /> > >> activation time is 2016-01-11 00:00:00 UTC.<br /> > >><br /> > >> Activation is achieved when 750 of 1,000 consecutive blocks in t= he<br /> > >> best chain have a version number with bits 3 and 14 set (0x20000= 004<br /> > >> in hex). The activation time will be the timestamp of the 750= 9;th<br /> > >> block plus a two week (1,209,600 second) grace period to give an= y<br /> > >> remaining miners or services time to upgrade to support larger<b= r /> > >> blocks. If a supermajority is achieved more than two weeks befor= e<br /> > >> 2016-01-11 00:00:00 UTC, the activation time will be 2016-01-11<= br /> > >> 00:00:00 UTC.<br /> > >><br /> > >> Block version numbers are used only for activation; once activat= ion<br /> > >> is achieved, the maximum block size shall be as described in the= <br /> > >> specification section, regardless of the version number of the<b= r /> > >> block.<br /> > >><br /> > >><br /> > >> ==Rationale==<br /> > >><br /> > >> The initial size of 8,000,000 bytes was chosen after testing the= <br /> > >> current reference implementation code with larger block sizes an= d<br /> > >> receiving feedback from miners stuck behind bandwidth-constraine= d<br /> > >> networks (in particular, Chinese miners behind the Great Firewal= l<br /> > >> of China).<br /> > >><br /> > >> The doubling interval was chosen based on long-term growth trend= s<br /> > >> for CPU power, storage, and Internet bandwidth. The 20-year limi= t<br /> > >> was chosen because exponential growth cannot continue forever.<b= r /> > >><br /> > >> Calculations are based on timestamps and not blockchain height<b= r /> > >> because a timestamp is part of every block's header. This al= lows<br /> > >> implementations to know a block's maximum size after they ha= ve<br /> > >> downloaded it's header, but before downloading any transacti= ons.<br /> > >><br /> > >> The deployment plan is taken from Jeff Garzik's proposed BIP= 100<br /> > >> block size increase, and is designed to give miners, merchants,<= br /> > >> and full-node-running-end-users sufficient time to upgrade to<br= /> > >> software that supports bigger blocks. A 75% supermajority was<br= /> > >> chosen so that one large mining pool does not have effective vet= o<br /> > >> power over a blocksize increase. The version number scheme is<br= /> > >> designed to be compatible with Pieter's Wuille's propose= d "Version<br /> > >> bits" BIP.<br /> > >><br /> > >> TODO: summarize objections/arguments from<br /> > >> <a href=3D"http://gavinandresen.ninja/time-to-roll-out-bigger-bl= ocks">http://gavinandresen.ninja/time-to-roll-out-bigger-blocks</a>.<br /> > >><br /> > >> TODO: describe other proposals and their advantages/disadvantage= s<br /> > >> over this proposal.<br /> > >><br /> > >><br /> > >> ==Compatibility==<br /> > >><br /> > >> This is a hard-forking change to the Bitcoin protocol; anybody<b= r /> > >> running code that fully validates blocks must upgrade before the= <br /> > >> activation time or they will risk rejecting a chain containing<b= r /> > >> larger-than-one-megabyte blocks.<br /> > >><br /> > >> Simplified Payment Verification software is not affected, unless= <br /> > >> it makes assumptions about the maximum depth of a transaction= 9;s<br /> > >> merkle branch based on the minimum size of a transaction and the= <br /> > >> maximum block size.<br /> > >><br /> > >> ==Implementation==<br /> > >><br /> > >> <a href=3D"https://github.com/gavinandresen/bitcoinxt/tree/block= size_fork">https://github.com/gavinandresen/bitcoinxt/tree/blocksize_fork</= a><br /> > >><br /> > >><br /> > >><br /> > >> _______________________________________________ bitcoin-dev mail= ing<br /> > >> list <a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org= ">bitcoin-dev@lists.linuxfoundation.org</a><br /> > >> <a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bi= tcoin-dev">https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev</= a><br /> > >><br /> > ><br /> > > - --<br /> > > <a href=3D"http://abis.io">http://abis.io</a> ~<br /> > > "a protocol concept to enable decentralization<br /> > > and expansion of a giving economy, and a new social good"<br /> > > <a href=3D"https://keybase.io/odinn">https://keybase.io/odinn</a><br= /> > > -----BEGIN PGP SIGNATURE-----<br /> > > Version: GnuPG v1<br /> > ><br /> > > iQEcBAEBAgAGBQJVigtJAAoJEGxwq/inSG8CqZwIAIG3ZQzekfccPxBOMqtim175<br = /> > > Crov6hrO9FaIzbLljECpUi60RKuDM/fs09ZJsKKIaJPkB5dlJjs4huc206veAIO+= <br /> > > K2h3DmAcA6W/Thk0C2cV3ewv+OiELDOhpeoddBBLPadAfaBGr4l9ltqWLdBtMCmw= <br /> > > OtmiWstEuXTao9ApgoFOmybdmCjbfrfhejOOHs/pMiSn5xVE60RK4x2HFTFsHfAN<br = /> > > fZAeLCuwuN2qWMrVrr+cbpCXjEuE1xZG3WEj7ppYoGR+AgF/Y5/U1j7S4PVp= k85s<br /> > > CgMkpcWvLnBMmSCrllnRZy1Gfrwk36Pg0rXD/l/NNd0/KTpmPSvkX/bCyzFwbzo== <br /> > > =ft62<br /> > > -----END PGP SIGNATURE-----<br /> > > _______________________________________________<br /> > > bitcoin-dev mailing list<br /> > > <a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin= -dev@lists.linuxfoundation.org</a><br /> > > <a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoi= n-dev">https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev</a><b= r /> > ><br /> > _______________________________________________<br /> > bitcoin-dev mailing list<br /> > <a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev&= #64;lists.linuxfoundation.org</a><br /> > <a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev= ">https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev</a><br /> > </div></div></blockquote></div><br /></div> > </blockquote></div><br />_______________________________________________<= br /> > bitcoin-dev mailing list<br /> > <a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev&= #64;lists.linuxfoundation.org</a><br /> > <a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev= ">https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev</a><br /> > <br /></blockquote></div> > </blockquote></div> > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev