There are a few key points here. First, Ilya's slides are out of date. The reference set got removed (it was a complexity nightmare), so there's a bit less eff

There are a few key points here. First, Ilya's slides are out of date. The reference set got removed (it was a complexity nightmare), so there's a bit less efficiency in deltas but a substantially simpler algorithm for header sets. As for your badly behaved router, there are two options. The first is that it's a router, not a proxy. In that case, the strict ordering of TCP ensures that there's no problem here. A router cannot cause the server to miss a request without knowing about it. Assuming by 'router' you meant 'proxy', the key here is that HPACK compression state is hop-by-hop, not end-to-end. That is, HPACK compression state is only synchronised at each end of a TCP connection. The strict ordering of TCP ensures that those two ends cannot be confused about the order of requests. Across TCP connections, there's new HPACK state.