IRC meeting summary for 2016-06-16


Main topics

  • Compactblock and feature freeze
  • Segwit update
  • Replacements with RBF in 0.13
  • GetBlockTemplate (GBT)

Compactblock and feature freeze


BIP152: “Compact block relay” is a proposed idea for decreasing the bandwidth used during block relay by using short transaction IDs for transactions that should be in the mempool of the node. As a side-effect this also results in reducing the block transfer latency. Read the compact blocks FAQ for more information.

meeting comments

Sipa proposes to push the feature freeze one week back for compact block and segwit to stabilize. Wumpus doesn’t like that idea since the feature freeze is already pushed back a month. Sdaftuar doesn’t think compact blocks is ready right now as it still has outstanding issues. Wumpus notes bugs can still be fixed after it’s merged as release candidate 1 is on July 7th.

Nobody would like to see segwit without compactblocks, as blocks will become effectively bigger.

meeting conclusion

  • Have another week to fix bugs and re-evaluate next Thursday.

Segwit update


Developers are working on a soft fork to introduce segregated witness onto Bitcoin mainnet. Segregated witness (segwit) allows transaction signature data to be stored outside of the data hashed to produce transaction identifiers, removing all known forms of third-party malleability, allowing full nodes to compile the current UTXO set without downloading all signatures, and laying the groundwork for fraud proofs that can allow lightweight (SPV) clients to help enforce more of the consensus rules. The segwit soft fork also allows miners to substitute 1 byte of block space with 4 bytes of segwit data, increasing transaction capacity for wallets that use segwit. segregated witness BIPs: BIP141, BIP142, BIP143, BIP144 and BIP145

meeting comments

Sipa thinks there won’t be any further changes necessary apart from making it cooperate with compact blocks. Question is whether to merge segwit before compact blocks or not. Compact blocks is smaller to review and it has got fewer review than segwit, but on the other hand segwit isn’t bound by the feature freeze as it just needs to be in master, not 0.13.0. However merging it before 0.13.0 would make things more testable/tested.

Sipa points to PR #8149 which has the commits organized per BIP, which might make sense for some people to review that and just ACK certain sections of it. He has a list of commits in the comments organized per section which he keeps up to date.

meeting conclusion

  • More review on compactblocks and segwit

Replacements with RBF in 0.13


BIP125 Opt-in replace-by-fee (RBF) is a new feature since 0.12 which enables wallets to mark transactions as replaceable while they’re still in the mempool. This allows wallets to bump fees, add recipients, etc. More information can be found on the RBF FAQ page. Currently the bitcoin-core wallet doesn’t offer any functionality to use these features.

meeting comments

Jonasschnelli thinks we should have a replacement option for the wallet in 0.13. He’d like review on PR #8182 which is a GUI bumpfee command. Everyone would like to see a bump fee option, however it’s very late now and getting compact blocks and segwit in might be enough worry for next week.

Petertodd suggests to get at least his global opt-in setting in, so people who need RBF can easily use external scripts to do so.

meeting conclusion

GetBlockTemplate (GBT)


Getblocktemplate is the new decentralized Bitcoin mining protocol, openly developed by the Bitcoin community over mid 2012. It supersedes the old getwork mining protocol. (Wiki-link)

meeting comments

Luke-jr asks how GBT should react to pre-segwit miners, once segwit activates. Currently it gets errors which causes the miner to failover or stop. Alternatively you could mine blocks without any witness transactions or return an empty block. Empty blocks is less desirable overall, however it’s much more likely to get noticed and upgraded and doesn’t bring that much code complexity.

Sdaftuar remarks those blocks will get orphaned if there’s a failover to an old daemon, which will get noticed too. This because segwit nodes will try to download blocks from witness peers and thus non-witness blocks won’t get relayed. Petertodd however remarks only one node in the network that bridges the gap between non-witness and witness peers makes it so it does relay.

meeting conclusion

  • Keep the current behavior and reconsider if miners complain about it.


IRC nick Name/Nym
Luke-jr Luke Dashjr
jonasschnelli Jonas Schnelli
petertodd Peter Todd
sipa Pieter Wuille
gmaxwell Gregory Maxwell
wumpus Wladimir van der Laan
instagibbs Gregory Sanders
btcdrak BtcDrak
jeremyrubin Jeremy Rubin
sdaftuar Suhas Daftuar
BakSAj BakSAj
phantomcircuit Patrick Strateman
achow101 Andrew Chow


This summary was compiled without input from any of the participants in the discussion, so any errors are the fault of the summary author and not the discussion participants.

Show your support