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

Without looking at the implementation, I would imagine that packet C also includes the id of the packet it is the delta from (in this case, packet B).

When the client receives packet C following packet A, it will know that it hasn't seen packet B yet, and can consequently request a full update from the server.