Noel; > > From: Caitlin Bestler <caitlinb@rp.asomi.net> > > > Given the source interface, the *meaning* of an IP header is not > > supposed to be dependent on the routing tables. .. > > By contrast, the meaning of an ATM circuit is dependent on the context > > in which it was established. There is no expectation that there is any > > meaning to this circuit identifier beyond those imparted when the > > circuit was created. > > Yes, but that's just a minor engineering decisions, i.e. the use of a That's the essential requirement for networks capable of best effort service to let all the packets have globally routable addresses. > non-global namespace for circuit ID's. It's easy to imagine an ATM-like system > in which circuit ID's are global in scope. RSVP is a case. > The real crucial *architectural* difference is in the fact that there is > per-flow state, along with the need to set up state before the packets can > flow. RSVP establishes the per-flow state before the packets can flow. It is just a minor engineering decision to allow optional circuit switched service over a best-effort-capable network. Masataka Ohta