Datagram Forwarding via Stateless Internetwork Switching

Gregory Finn, Craig Milo Rogers, Rodney Van Meter
Information Sciences Institute
University of Southern California
Marina del Rey, CA 90292
finn@isi.edu, hotz@isi.edu, rdv@isi.edu
(310) 822-1511

Abstract:

Circuit switching achieves high forwarding performance via the combination of a hardware frame forwarding path and link-layer connection state that is stored in each switch along a virtual circuit. A similar result can be achieved when forwarding datagrams across an internetwork by uncoupling forwarding from hop-by-hop routing. That uncoupling is achieved by using a specialized network-layer protocol to wrap the datagram of another network-layer protocol with a source route that is derived by consulting hop-by-hop routing tables. Properly formatted source-routed datagrams can be forwarded by switching. Locating complete forwarding state in each datagram considerably simplifies switch design and the source route need be cached only at the head of the route. Periodically, re-deriving these source routes achieves the adaptability needed to maintain compatibility with connectionless datagram routing.


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