Published on: 2021-07-29T11:36:25+00:00
During the recent online Sydney Socratic Seminar, the discussion centered around L2 on-chain support. The session delved into the rules of BIP 125 RBF and explored proposed ideas such as SIGHASH_IOMAP, fee sponsorship, and transaction mutation. These topics were not covered in the previous IRC workshops. A transcript of the session can be found at https://btctranscripts.com/sydney-bitcoin-meetup/2021-07-06-socratic-seminar/.The second workshop, held on June 29, 2021, focused on fee bumping and package relay. Detailed information on package relay can be accessed at https://github.com/ariard/L2-zoology/blob/master/workshops/package-relay-and-friends.md. Attendees discussed the possibility of enabling two transaction packages for Lightning and DLCs. Package RBF (replace-by-fee) was considered if there are two competing packages containing competing Lightning commitment transactions. The concept of using hints instead of relaying entire transactions to communicate information about fetching the rest of the package was also explored.The workshop also examined witness replacement and Taproot. It was suggested that a future soft fork could give meaning to the annex in Taproot, which could be utilized to inflate the fee rate of a witness. However, it was noted that the annex can only increase the weight of a transaction, not decrease it. The goals of the session were to assess whether two transaction packages would adequately support existing L2 protocols, discuss ongoing debates regarding the deprecation of opt-in RBF and implementation of full RBF, establish a policy for responding to cross-layer security issues, and develop a consensus on L2 security philosophy design with minimal assumptions on the base layer.The attendees of the second workshop agreed that enabling two transaction packages would be sufficient for Lightning and DLCs. They proposed a two-step process where the first transaction has an effective zero fee rate and the second transaction sets the fee. Implementing RBF within a package was considered complex and harder to reason about. Therefore, the suggestion of having two packages {A,B} and {B,C} was put forward if three transaction packages were not supported.Regarding the communication of hints instead of relaying transactions, concerns were raised about the successful propagation of these hints across the network. Tapscripts, which can be unlimited in size, were discussed in relation to Taproot rules, allowing for a transition from a 100,000 vbyte witness to an empty witness. The potential usefulness of package relay for L2 protocols was highlighted as a way to address the unpredictability of future fees. Notably, prior work has been done on package relay, primarily by Suhas Daftuar, and Gloria Zhao has been advancing this concept in Bitcoin Core.The participants agreed that enabling two transaction packages would suffice for Lightning and DLCs, at least for the time being. The background and design questions regarding package relay were also explored. CPFP (Child Pays For Parent) was mentioned as a mechanism to ensure the confirmation of a lower-fee justice transaction in Lightning by incentivizing miners to include the child transaction in a block. It was suggested that broadcasting a high fee CPFP transaction for the {A,B} package might be preferable to creating two separate packages. If the first package is evicted from the mempool, the {B,C} package would not propagate as it would become an orphan package. Additionally, the idea of a package-based CBlockPolicyEstimator in Bitcoin Core was proposed by darosior, considering the increasing use of CPFP on the network.Overall, the workshops provided valuable insights into L2 support, fee bumping, package relay, and the ongoing discussions and developments in the Bitcoin ecosystem.
Updated on: 2023-07-31T23:31:23.707287+00:00