On Mon, Dec 11, 2017 at 8:40 PM, Jim Posen via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote: > Firstly, I don't like the idea of making the net header encoding dependent > on the specific header validation rules that Bitcoin uses (eg. the fact that > difficulty is only recalculated every 2016 blocks). This would be coupling
In the last proposal I recall writing up, there was a one byte flag on each header to indicate what was included. Nbits _never_ needs to be sent even with other consensus rules because its more or less necessarily a strict function of the prior headers. This still holds in every clone of Bitcoin I'm aware of; sending it with the first header in a group probably makes sense so it can be checked independently. > with insufficient benefit. another >18% reduction in size beyond the removal of prev. is not insubstantial by any means. I don't think it should lightly be ignored. Prev omission itself is not, sadly, magically compatible: I am quite confident that if there is a bitcoin hardfork it would recover the nbits/4-guarenteed always-zero bits of prev to use as extra nonce for miners. This has been proposed many times, implemented at least once, and the current requirement for mining infrastructure to reach inside the coinbase txn to increment a nonce has been a reliable source of failures. So I think we'd want to have the encoding able to encode leading prev bits. Many altcoins also change the header structures. If the better thing is altcoin incompatible, we should still do it. Doing otherwise would competitively hobble Bitcoin especially considering the frequent recklessly incompetent moves made by various altcoins and the near total lack of useful novel development we've seen come out of the clones. Probably the most important change in a new header message wouldn't be the encoding, but it would be changing the fetching mechanism so that header sets could be pulled in parallel, etc. I would rather not change the serialization of existing messages, nodes are going to have to support speaking both messages for a long time, and I think we already want a different protocol flow for headers fetching in any case. _______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
