Δ - an upper bound on maximum message delays
f - an upper bound on faulty processes a protocol can tolerate
stage - a Δ length period of time when a node tries to find a convincing message and potentially convince others
Synchrony is enforced by each process starting with the current system's time. The timestamp of beginning of stage 0 is hardcoded in the protocol (5 seconds after launching a process).
Each subsequent stages' timestamps can be derived from this common knowledge by simple math (since protocol's expected message delay is also known):
where Δ is an expected message delay
Because we are in a synchronous model, all nodes have a notion of shared global clock and an upper bound on message delays.
For every f number of Byzantine processes we want to tolerate, we run a "stage" of a dolev-strong strong consensus protocol,
when a node tries to get convinced of some value (that will potentially be outputted) and subsequently convince others.
A node i is considered convinced of value v at some stage S if it received such a message that:
- it references value
v - it is signed first by a sender
- it is signed by ``>= S
other distinct nodes, none of which are nodei`
A Dolev-Strong protocol can tolerate as many Byzantine nodes F as anyone would want. But for any Byzantine node that the protocol wants to tolerate, it has to go through one more stage during consensus.