On Wed, Aug 19, 2015 at 7:10 AM, Mark Friedenbach via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:

We can use nVersion & 0x8 to signal support, while keeping the consensus rule as nVersion >= 4, right? That way we don't waste a bit after this all clears up.

What happens if XT gets 40% and this BIP gets 55%? That gives 95% that accept the upgrade. Version 3 and lower blocks need to be rejected after that.

By advertising 0x7 for the last 3 bits, XT is effectively claiming to support the check locktime verify BIPs but they don't have the code.

This sequence could be used, without a specific version-bits proposal.

Until height = N + 5000, if 950 of the last 1000 blocks have the 0x8 bit set, then reject blocks with version numbers less than 8.

At height N, if the above rule is active, then the BIP is permanent.

It applies to any block with bit 0x8 set, once the 75% threshold is met.

From height N + 5000 to N + 10000, reject blocks which have bit 0x8 set.

N could be set 1 year from now, or so.

This gives a period of time after lock that bit 8 is kept and then a period where is is guaranteed to be zero.

This gives software that is only watching the bit time to be upgraded and similarly time where the bit is set to zero before it can be reused.