[bitcoin-dev] Segregated Witness in the context of Scaling Bitcoin

jl2012 jl2012 at xbt.hk
Thu Dec 17 05:32:11 UTC 2015

There are at least 2 proposals on the table:

1. SWSF (segwit soft fork) with 1MB virtual block limit, approximately 
equals to 2MB actual limit

2. BIP102: 2MB actual limit

Since the actual limits for both proposals are approximately the same, 
it is not a determining factor in this discussion

The biggest advantage of SWSF is its softfork nature. However, its 
complexity is not comparable with any previous softforks we had. It is 
reasonable to doubt if it could be ready in 6 months

For BIP102, although it is a hardfork, it is a very simple one and could 
be deployed with ISM in less than a month. It is even simpler than 
BIP34, 66, and 65.

So we have a very complicated softfork vs. a very simple hardfork. The 
only reason makes BIP102 not easy is the fact that it's a hardfork.

The major criticism for a hardfork is requiring everyone to upgrade. Is 
that really a big problem?

First of all, hardfork is not a totally unknown territory. BIP50 was a 
hardfork. The accident happened on 13 March 2013. Bitcoind 0.8.1 was 
released on 18 March, which only gave 2 months of grace period for 
everyone to upgrade. The actual hardfork happened on 16 August. 
Everything completed in 5 months without any panic or chaos. This 
experience strongly suggests that 5 months is already safe for a simple 
hardfork. (in terms of simplicity, I believe BIP102 is even simpler than 

Another experience is from BIP66. The 0.10.0 was released on 16 Feb 
2015, exactly 10 months ago. I analyze the data on 
https://bitnodes.21.co and found that 4600 out of 5090 nodes (90.4%) 
indicate BIP66 support. Considering this is a softfork, I consider this 
as very good adoption already.

With the evidence from BIP50 and BIP66, I believe a 5 months 
pre-announcement is good enough for BIP102. As the vast majority of 
miners have declared their support for a 2MB solution, the legacy 1MB 
fork will certainly be abandoned and no one will get robbed.

My primary proposal:

Now - 15 Jan 2016: formally consult the major miners and merchants if 
they support an one-off rise to 2MB. I consider approximately 80% of 
mining power and 80% of trading volume would be good enough

16 - 31 Jan 2016: release 0.11.3 with BIP102 with ISM vote requiring 80% 
of hashing power

1 Jun 2016: the first day a 2MB block may be allowed

Before 31 Dec 2016: release SWSF

My secondary proposal:

Now: Work on SWSF in a turbo mode and have a deadline of 1 Jun 2016

1 Jun 2016: release SWSF

What if the deadline is not met? Maybe pushing an urgent BIP102 if 
things become really bad.

In any case, I hope a clear decision and road map could be made now. 
This topic has been discussed to death. We are just bringing further 
uncertainty if we keep discussing.

Matt Corallo via bitcoin-dev 於 2015-12-16 15:50 寫到:
> A large part of your argument is that SW will take longer to deploy
> than a hard fork, but I completely disagree. Though I do not agree
> with some people claiming we can deploy SW significantly faster than a
> hard fork, once the code is ready (probably a six month affair) we can
> get it deployed very quickly. It's true the ecosystem may take some
> time to upgrade, but I see that as a feature, not a bug - we can build
> up some fee pressure with an immediate release valve available for
> people to use if they want to pay fewer fees.
>  On the other hand, a hard fork, while simpler for the ecosystem to
> upgrade to, is a 1-2 year affair (after the code is shipped, so at
> least 1.5-2.5 from today if we all put off heads down and work). One
> thing that has concerned me greatly through this whole debate is how
> quickly people seem to think we can roll out a hard fork. Go look at
> the distribution of node versions on the network today and work
> backwards to get nearly every node upgraded... Even with a year
> between fork-version-release and fork-activation, we'd still kill a
> bunch of nodes and instead of reducing their security model, lead them
> to be outright robbed.

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