Your BIP implementation should stress the capacity to softfork the rate of blocksize increase if necessary. You briefly mention that: 

If over time, this growth factor is beyond what the actual technology offers, the intention should be to soft fork a tighter limit.

However this can work both ways so that the rate can potentially be increased also. I think just mentioning this will soothe a lot of future critiques.

Daniele



Message: 5
Date: Fri, 27 Jan 2017 01:06:59 +0000
From: Luke Dashjr <luke@dashjr.org>
To: bitcoin-dev@lists.linuxfoundation.org
Subject: [bitcoin-dev] Three hardfork-related BIPs
Message-ID: <201701270107.01092.luke@dashjr.org>
Content-Type: Text/Plain;  charset="utf-8"

I've put together three hardfork-related BIPs. This is parallel to the ongoing
research into the MMHF/SHF WIP BIP, which might still be best long-term.

1) The first is a block size limit protocol change. It also addresses three
criticisms of segwit: 1) segwit increases the block size limit which is
already considered by many to be too large; 2) segwit treats pre-segwit
transactions ?unfairly? by giving the witness discount only to segwit
transactions; and 3) that spam blocks can be larger than blocks mining
legitimate transactions. This proposal may (depending on activation date)
initially reduce the block size limit to a more sustainable size in the short-
term, and gradually increase it up over the long-term to 31 MB; it will also
extend the witness discount to non-segwit transactions. Should the initial
block size limit reduction prove to be too controversial, miners can simply
wait to activate it until closer to the point where it becomes acceptable
and/or increases the limit. However, since the BIP includes a hardfork, the
eventual block size increase needs community consensus before it can be
deployed. Proponents of block size increases should note that this BIP does
not interfere with another more aggressive block size increase hardfork in the
meantime. I believe I can immediately recommend this for adoption; however,
peer and community review are welcome to suggest changes.
Text: https://github.com/luke-jr/bips/blob/bip-blksize/bip-blksize.mediawiki
Code: https://github.com/bitcoin/bitcoin/compare/master...luke-jr:bip-blksize
(consensus code changes only)

2) The second is a *preparatory* change, that should allow trivially
transforming certain classes of hardforks into softforks in the future. It
essentially says that full nodes should relax their rule enforcement, after
sufficient time that would virtually guarantee they have ceased to be
enforcing the full set of rules anyway. This allows these relaxed rules to be
modified or removed in a softfork, provided the proposal to do so is accepted
and implemented with enough advance notice. Attempting to implement this has
proven more complicated than I originally expected, and it may make more sense
for full nodes to simply stop functioning (with a user override) after the
cut-off date). In light of this, I do not yet recommend its adoption, but am
posting it for review and comments only.
Text: https://github.com/luke-jr/bips/blob/bip-hfprep/bip-hfprep.mediawiki

3) Third is an anti-replay softfork which can be used to prevent replay
attacks whether induced by a hardfork-related chain split, or even in ordinary
operation. It does this by using a new opcode (OP_CHECKBLOCKATHEIGHT) for the
Bitcoin scripting system that allows construction of transactions which are
valid only on specific blockchains.
Text: https://github.com/luke-jr/bips/blob/bip-noreplay/bip-noreplay.mediawiki

Luke

Daniele Pinna, Ph.D