QoS Performance Comparison Between Combined Input and Crosspoint Queueing Switches and Output Queueing Switches

Q. Duan (USA)


QoS, packet switch, OQ emulation, network calculus.


Packet switches play one of the most critical roles in sup porting Quality of Service (QoS) in computer communica tion networks. Although the output queueing (OQ) switch architecture can achieve the optimal QoS performance, it is not practical for high speed switching due to its complexity. Combined input and crosspoint queueing (CICQ) switches are promising to achieve high performance without com plex implementation. However, the current available ap proach for providing QoS in CICQ switches is based on emulating OQ switches, which will significantly compli cate the traffic control in CICQ switches. In this paper, we will investigate the possibility of achieving identical QoS performance in CICQ switches as in OQ switches without employing the complex output queueing emulation. To ward this end, we apply the network calculus technique to model and analyze traffic control systems in CICQ and OQ switches, then compare QoS provision capabilities of CICQ switches with that of OQ switches. We find that CICQ switches can provide identical bandwidth guarantee as OQ switches by allocating sufficient crosspoint buffer space, and can achieve equivalent delay performance as OQ switches by slightly increasing bandwidth allocation.

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