Re: [bitcoin-dev] Height based vs block time based thresholds

From: "Hampus Sjöberg" <hampus.sjoberg@gmail•com>
To: Luke Dashjr <luke@dashjr•org>
Cc: "bitcoin-dev@lists•linuxfoundation.org"
	<bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] Height based vs block time based thresholds
Date: Wed, 5 Jul 2017 21:44:27 +0200	[thread overview]
Message-ID: <CAFMkqK9ezq_AdOpeA08jpr9haHP_jEHaJaQ2KZC=yMy6UXaJyA@mail.gmail.com> (raw)
In-Reply-To: <201707050410.45217.luke@dashjr.org>

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From the PR change:

> Miners must continue setting the bit in LOCKED_IN phase so uptake is
visible and acknowledged. Blocks without the applicable bit set are invalid
during this period

Luke, it seems like the amendments to BIP8 make it drastically different to
how it first was designed to work.
It now looks more akin to BIP148, which was AFAICT not how BIP8 was
originally intended to work.
Perhaps this should be made into its own BIP instead, or make it so it's
possible to decide how the LOCKED_IN state should work when designing the
softfork.

Hampus

2017-07-05 6:10 GMT+02:00 Luke Dashjr via bitcoin-dev <
bitcoin-dev@lists•linuxfoundation.org>:

> It's not pointless: it's a wake-up call for miners asleep "at the wheel",
> to
> ensure they upgrade in time. Not having a mandatory signal turned out to
> be a
> serious bug in BIP 9, and one which is fixed in BIP 148 (and remains a
> problem
> for BIP 149 as-is). Additionally, it makes the activation decisive and
> unambiguous: once the lock-in period is complete, there remains no
> question as
> to what the correct protocol rules are.
>
> It also enables deploying softforks as a MASF, and only upgrading them to
> UASF
> on an as-needed basis.
>
> Luke
>
>
> On Wednesday 05 July 2017 4:00:38 AM shaolinfry wrote:
> > Luke,
> > I previously explored an extra state to require signalling before
> > activation in an earlier draft of BIP8, but the overall impression I got
> > was that gratuitous orphaning was undesirable, so I dropped it. I
> > understand the motivation behind it (to ensure miners are upgraded), but
> > it's also rather pointless when miners can just fake signal. A properly
> > constructed soft fork is generally such that miners have to deliberately
> > do something invalid - they cannot be tricked into it... and miners can
> > always chose to do something invalid anyway.
> >
> > > -------- Original Message --------
> > > From: luke@dashjr•org
> > > To: bitcoin-dev@lists•linuxfoundation.org, shaolinfry
> > > <shaolinfry@protonmail•ch> I"ve already opened a PR almost 2 weeks ago
> > > to do this and fix the other issues BIP 9 has.
> > > https://github.com/bitcoin/bips/pull/550
> > > It just needs your ACK to merge.
> > >
> > > On Wednesday 05 July 2017 1:30:26 AM shaolinfry via bitcoin-dev wrote:
> > >> Some people have criticized BIP9"s blocktime based thresholds arguing
> > >> they are confusing (the first retarget after threshold). It is also
> > >> vulnerable to miners fiddling with timestamps in a way that could
> > >> prevent or delay activation - for example by only advancing the block
> > >> timestamp by 1 second you would never meet the threshold (although
> this
> > >> would come a the penalty of hiking the difficulty dramatically). On
> the
> > >> other hand, the exact date of a height based thresholds is hard to
> > >> predict a long time in advance due to difficulty fluctuations.
> However,
> > >> there is certainty at a given block height and it"s easy to monitor.
> If
> > >> there is sufficient interest, I would be happy to amend BIP8 to be
> > >> height based. I originally omitted height based thresholds in the
> > >> interests of simplicity of review - but now that the proposal has been
> > >> widely reviewed it would be a trivial amendment.
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