[bitcoin-dev] Segwit2Mb - combined soft/hard fork - Request For Comments

Natanael natanael.l at gmail.com
Sat Apr 1 15:34:24 UTC 2017

Den 1 apr. 2017 16:07 skrev "Jorge Timón" <jtimon at jtimon.cc>:

On Sat, Apr 1, 2017 at 3:15 PM, Natanael <natanael.l at gmail.com> wrote:
> Den 1 apr. 2017 14:33 skrev "Jorge Timón via bitcoin-dev"
> <bitcoin-dev at lists.linuxfoundation.org>:
> Segwit replaces the 1 mb size limit with a weight limit of 4 mb.
> That would make it a hardfork, not a softfork, if done exactly as you say.
> Segwit only separates out signature data. The 1 MB limit remains, but
> now only cover the contents of the transaction scripts. With segwit that
> means we have two (2) size limits, not one. This is important to remember.
> Even with segwit + MAST for large complex scripts, there's still going to
> a very low limit to the total number of possible transactions per block.
> not all transactions will get the same space savings.

No, because of the way the weight is calculated, it is impossible to
create a block that old nodes would perceive as bigger than 1 mb
without also violating the weight limit.
After segwit activation, nodes supporting segwit don't need to
validate the 1 mb size limit anymore as long as they validate the
weight limit.


Huh, that's odd. It really does still count raw blockchain data blocksize.

It just uses a ratio between how many units each byte is worth for block
data vs signature data, plus a cap to define the maximum. So the current
max is 4 MB, with 1 MB of non-witness blockchain data being weighted to 4x
= 4 MB. That just means you replaced the two limits with one limit and a

A hardfork increasing the size would likely have the ratio modified too.
With exactly the same effect as if it was two limits...

Either way, there's still going to be non-segwit nodes for ages.
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