Re: [bitcoin-dev] [BIP Proposal] Version bits with timeout and delay.

From: "Jorge Timón" <jtimon@jtimon•cc>
To: Rusty Russell <rusty@rustcorp•com.au>
Cc: Bitcoin Dev <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] [BIP Proposal] Version bits with timeout and delay.
Date: Wed, 16 Sep 2015 22:27:33 +0200	[thread overview]
Message-ID: <CABm2gDqh=Dv2Ygctg+jEt61N_nJDRBMqdZypSPtmfM2QrY4AYQ@mail.gmail.com> (raw)
In-Reply-To: <87r3lyjewl.fsf@rustcorp.com.au>

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For enforcing new restrictions on your own blocks (thus at the policy
level, not consensus) you don't need to wait for 75%. You can do it from
the start (this way all miners setting the bit will enforce the new
restrictions.
On Sep 16, 2015 4:20 PM, "Rusty Russell via bitcoin-dev" <
bitcoin-dev@lists•linuxfoundation.org> wrote:

> Tier Nolan via bitcoin-dev <bitcoin-dev@lists•linuxfoundation.org>
> writes:
> > On Sun, Sep 13, 2015 at 7:56 PM, Rusty Russell via bitcoin-dev <
> > bitcoin-dev@lists•linuxfoundation.org> wrote:
> >
> >> '''States'''
> >> With every softfork proposal we associate a state BState, which begins
> >> at ''defined'', and can be ''locked-in'', ''activated'',
> >> or ''failed''.  Transitions are considered after each
> >> retarget period.
> >>
> >
> > I think the 75% rule should be maintained.  It confirms that miners who
> are
> > setting the bit are actually creating blocks that meet the new rule
> (though
> > it doesn't check if they are enforcing it).
>
> I couldn't see a use for it, since partial enforcement of a soft fork is
> pretty useless.
>
> Your point about checking that miners are actually doing it is true,
> though all stuff being forked in in future will be nonstandard AFAICT.
>
> I bias towards simplicity for this.
>
> > What is the reason for aligning the updated to the difficulty window?
>
> Miners already have that date in their calendar, so prefer to anchor to
> that.
>
> > *defined*
> > Miners set bit
> > If 75% of blocks of last 2016 have bit set, goto tentative
> >
> >
> > *tentative*
> > Miners set bit
> > Reject blocks that have bit set that don't follow new rule
> > If 95% of blocks of last 2016 have bit set, goto locked-in
> >
> >
> > *locked-in*
> >
> > Point of no return
> > Miners still set bit
> > Reject blocks that have bit set that don't follow new rule
> > After 2016 blocks goto notice
>
> OK, *that* variant makes perfect sense, and is no more complex, AFAICT.
>
> So, there's two weeks to detect bad implementations, then you everyone
> stops setting the bit, for later reuse by another BIP.
>
> > I think counting in blocks is easier to be exact here.
>
> Easier for code, but harder for BIP authors.
>
> > If two bits were allocated per proposal, then miners could vote against
> > forks to recover the bits.  If 25% of the miners vote against, then that
> > kills it.
>
> You need a timeout: an ancient (non-mining, thus undetectable) node
> should never fork itself off the network because someone reused a failed
> BIP bit.
>
> > In the rationale, it would be useful to discuss effects on SPV clients
> and
> > buggy miners.
> >
> > SPV clients should be recommended to actually monitor the version field.
>
> SPV clients don't experience a security change when a soft fork occurs?
> They're already trusting miners.
>
> Greg pointed out that soft forks tend to get accompanied by block forks
> across activation, but SPV clients should *definitely* be taking those
> into account whenever they happen, right?
>
> Thanks!
> Rusty.
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