From: Rusty Russell <rusty@rustcorp.com.au>
To: Gregory Maxwell <gmaxwell@gmail.com>
In-Reply-To: <87bncjph6c.fsf@rustcorp.com.au>
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	<87bncjph6c.fsf@rustcorp.com.au>
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Date: Fri, 02 Oct 2015 10:52:14 +0930
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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

Rusty Russell via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org>
writes:
> 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 :(

Actually, this isn't a decisive argument, since we can use the current
mechanism to upgrade versionbits, or as Eric says, tack it on to
an existing soft fork.

So, I think I'm back where I started.  We leave this for now.

There was no nak on the "keep setting bit until activation" proposal, so
I'm opening a PullReq for that now:

	https://github.com/bitcoin/bips/pull/209

Cheers,
Rusty.