Real-time multiplayer game (concept question)

Question

I\'ve been reading this article from Valve that seems to explain the architecture of their multiplayer system. It seems they delay rendering by a couple ticks on the client so t

Answer 1

The deltas don't have to be relative to the previous message that was sent (by delta or snapshot). Instead, they would be relative to the last acknowledged state. So in the example above, the update at C could be a delta relative to A. Losing message B therefore becomes an inconvenience as the deltas are getting larger (and potentially error is accumulating) but eventually a message will get through and be acknowledged, and the server can start sending deltas relative to that updated state.