[yangl1996]

Looks like there is no mentioning in the blogpost of the paper (poster) [1] in which the two-level broadcast idea is proposed.

[1] https://dl.acm.org/doi/pdf/10.1145/3548606.3563494

[ethan_smith]

The cited paper is indeed foundational, introducing not just two-level broadcast but also optimizations for validator selection and network topology that RaptorCast appears to build upon.

[compyman]

It seems very similar to an earlier paxos optimization called 'pig paxos' https://dl.acm.org/doi/10.1145/3448016.3452834