BIP Idea: incrementalrelayfee in feefilter?

The recent discussion in the Bitcoin Development Mailing List, initiated by Matt, addresses two significant challenges faced by users due to the current settings of minrelaytxfee and incrementalrelayfee in Core 30.0. Firstly, when a Replace-By-Fee (RBF) transaction is sent, it may be accepted by the user's node but rejected by peers if their incrementalrelayfee settings differ, leading to a situation where the transaction cannot proceed. Secondly, there is no way for users to ascertain the minimum RBF fee preferences of their peers since this information is not shared over the Peer-to-Peer (P2P) network. The only fee-related information currently exchanged is the minrelaytxfee through BIP133’s feefilter.

To address these issues, Matt proposes an extension to the feefilter message by including an incrementalrelayfee field. This modification would allow nodes to communicate their RBF policies openly, enabling users to connect with peers that have matching fee policies. The benefits of this proposal are multifaceted. It would notably reduce spam by preventing nodes from sending un-bumpable RBF transactions to peers, enhance transparency by allowing users to identify the RBF policies of other nodes, and facilitate the selection of compatible miner nodes for manual peer connections. Importantly, this change is framed as a policy adjustment without posing any risks to the consensus mechanism.

Matt expresses a willingness to spearhead the development of a prototype or draft a Bitcoin Improvement Proposal (BIP) if the community shows interest in this solution. This proactive approach emphasizes the importance of collaborative effort in refining and advancing Bitcoin's operational efficiency and user experience.