Abstract -The Internet is facing two problems simultaneously: there is a need for a faster switchinglrouting infrastructure, and a need to introduce guaranteed qualities of service (QoS). Each problem can be solved independently: switches and routers can be made faster by using input-queued crossbars, instead of shared memory systems; and QoS can be provided using WFQbased packet scheduling. However, until now, the two solutions have been mutually exclusive -all of the work on WFQ-based scheduling algorithms has required that switchedrouters use output-queueing, or centralized shared memory. This paper demonstrates that a Combined Input Output Queueing (CIOQ) switch running twice as fast as an input-queued switch can provide precise emulation of a broad class of packet scheduling algorithms, including WFQ and strict priorities. More precisely, we show that a "speedup" of 2 is sufficient, and a speedup of 2 -1/N is necessary, for this exact emulation. We introduce a variety of algorithms that configure the crossbar so that emulation is achieved with a speedup of two, and consider their running time and implementation complexity. An interesting feature of our work is that the exact emulation holds for all input traffic patterns. We believe that, in the future, these results will make possible the support of QoS in very high bandwidth routers.
In addition, Chuang et al. REF showed that a combined-input-output-buffered router can also emulate an output-buffered router.
Matching output queueing with a combined input output queued switch
IEEE INFOCOM '99. Conference on Computer Communications. Proceedings. Eighteenth Annual Joint Conference of the IEEE Computer and Communications Societies. The Future is Now (Cat. No.99CH36320)
IEEE INFOCOM '99. Conference on Computer Communications. Proceedings. Eighteenth Annual Joint Conference of the IEEE Computer and Communications Societies. The Future is Now (Cat. No.99CH36320)
Computer Science