Question about LibraBFT paper v2.0

Consensus
#1

In the paper advance_round(qc) method of pacemaker do send qc to new round leader, what is messgae type for this qc? I didn’t see any message type for this qc in the paper.

Procedure advance round(qc)
r ← qc.round
if r < current round then return
stop local timer for round r
current round ← r + 1
if u 6= ProposerElection.get leader(current round) then
  send qc to ProposerElection.get leader(current round)
start local timer for round current round for duration get round timer(current round)
Main.process new round event()
#2

If you’re asking about the implementation of how QCs are exchanged between validators, you can look at the code. When a proposal is sent (ProposalMsg), it contains a SyncInfo. When a VoteMsg is sent to the next proposer (or broadcast in a local timeout), it also contains a SyncInfo. SyncInfo contains the highest QC and timeout certificate (TC) so ensure all validators are on the latest round. Hope that helps!

#3

No, I just looked at Pseudocode in the paper. The code I pasted forward a QC to next leader however it is neither in proposal nor in timeout. Is this a special message which not mentioned?

#4

As mentioned previously, a VoteMsg can be sent to the next leader that contains the highest QC it knows about after a validator receives a ProposalMsg.