From: Rusty Russell <rusty@rustcorp.com.au>
To: Gregory Maxwell <gmaxwell@gmail.com>
In-Reply-To: <CAAS2fgTXP0j6K3sxp=HL9j2-xvO8y_VnpG+iZw9kaxmnxZQjSw@mail.gmail.com>
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	<CAAS2fgTXP0j6K3sxp=HL9j2-xvO8y_VnpG+iZw9kaxmnxZQjSw@mail.gmail.com>
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Date: Thu, 01 Oct 2015 09:56:51 +0930
Message-ID: <87bncjph6c.fsf@rustcorp.com.au>
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Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>,
	Pieter Wuille <pieter.wuille@gmail.com>
Subject: Re: [bitcoin-dev] Versionbits BIP (009) minor revision proposal.
Precedence: list

Gregory Maxwell <gmaxwell@gmail.com> writes:
> I can, however, argue it the other way (and probably have in the
> past):  The bit is easily checked by thin clients, so thin clients
> could use it to reject potentially ill-fated blocks from non-upgraded
> miners post switch (which otherwise they couldn't reject without
> inspecting the whole thing). This is an improvement over not forcing
> the bit, and it's why I was previously in favor of the way the
> versions were enforced.  But, experience has played out other ways,
> and thin clients have not done anything useful with the version
> numbers.
>
> A middle ground might be to require setting the bit for a period of
> time after rule enforcing begins, but don't enforce the bit, just
> enforce validity of the block under new rules.  Thus a thin client
> could treat these blocks with increased skepticism.

Introducing this later would trigger warnings on older clients, who
would consider the bit to represent a new soft fork :(

So if we want this middle ground, we should sew it in now, though it
adds a other state.  Simplest is to have miners keep setting the bit for
another 2016 blocks.  If we want to later, we can make this a consensus
rule.

"Bitcoin is hard, let's go shopping!"  "With Bitcoin!"  "..."
Rusty.