How to calculate number of messages in BFT?

Question

Do you know guys any mathematical equation for calculating the whole number of messages for agreement on one value in BFT (Byzantine Fault Tolerance) algorithm?

Let's say that N = 7 and f = 2

So, how can we calculate how many messages will be sent between nodes until the agreement on one value (consensus)?

Answer 1

It depends on the algorithm. Take a look on the PBFT paper (google it) - they have linear number of messages to agree on the operation. Today there are a lot of BFT algorithms with different optimisations. Some of them reduces number of messages as well. Tendermint and SBFT are good examples.

Disclaimer: I work on the SBFT algorithm implementation in VMWare.