Control-on-demand: an efficient approach to router programmability

摘要

Control-on-demand is a paradigm for network programmability at thennetwork transport level. Prior work on active and programmablennetworking at this level either achieves flexibility by insertingnsignificant software in the critical path of forwarding or achievesnefficiency by sacrificing functionality and relegating programmabilitynto connection management. In contrast, control-on-demand acts both innthe control plane and in the data plane, still without adding softwarenin the critical forwarding path. Rather than applying essential programsnto every datagram, our approach is to apply the installed service logicnasynchronously from data forwarding. This way we avoid essentialnprocessing in the critical forwarding path, applying the (user)ninstalled service logic for service enhancement only. In this paper, wendescribe control-on-demand and how its service model provides sufficientnrichness to act in the data path. Set is restrictive enough to avoid thensignificant performance overhead of other in-data path approaches. Thenexpressiveness of the programmable model is limited to observing andnsuggesting to the forwarding engine, but is never essential for correctnprocessing, thus significantly reducing security and robustnessnconcerns. Consequently, control-on-demand is efficient enough to make itnviable for elementary services. Rather than replacing theninteroperability layer, control-on-demand represents an evolution ofnrouter (switch) control functionality. As the required modification ofnrouter forwarding engines is insignificant, control-on-demand is viablenin practice in the near future. These concepts have been prototyped asnpart of the Pronto Control Platform. In this paper, we describe our IPv6nrouter prototype implementation and discuss the application ofncontrol-on-demand on a number of interesting problems