Avoiding speedup from bandwidth overhead in a practical output-queued packet switch

Lin Cai, Roberto Rojas-Cessa, Taweesak Kijkanjanarat

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations


This paper adopts a time-slotted and synchronous output-queued (SS-OQ) switch, which avoids memory speedup through the use of dedicated lines connecting inputs to outputs, to show that the performance of an S-OQ switch approaches that of an ideal OQ switch, or asynchronous OQ (A-OQ) switch. An A-OQ switch forwards packets to their destined outputs at arrival but it is costly to implement as immediate packet forwarding requires very high-speed hardware to identify the destination output and memory synchronization at the outputs. The dedicated lines of the SS-OQ switch induce the use of virtual input queues (VIQs) at the outputs, and time slotting requires the use of segmentation queues at the inputs. The segmentation of variable-length IP packets into fixed length cells causes transmission overhead that can be compensated with additional but undesirable speedup. However, segmentation queues can also be used for packet concatenation to reduce transmission overhead. This paper evaluates the improvement of bandwidth utilization in the concatenating SS-OQ (CS-OQ) switch through packet concatenation and segment length selection to decrease additional speedup needed to overcome the transmission overhead. The presented results show that a suitable segmentation length can be combined with packet concatenation to pair up the performance of the CS-OQ switch to that of an A-OQ switch.

Original languageEnglish (US)
Title of host publication2011 IEEE International Conference on Communications, ICC 2011
StatePublished - 2011
Event2011 IEEE International Conference on Communications, ICC 2011 - Kyoto, Japan
Duration: Jun 5 2011Jun 9 2011

Publication series

NameIEEE International Conference on Communications
ISSN (Print)0536-1486


Other2011 IEEE International Conference on Communications, ICC 2011

All Science Journal Classification (ASJC) codes

  • Computer Networks and Communications
  • Electrical and Electronic Engineering


  • Output queued switch
  • asynchronous switch
  • bandwidth utilization
  • concatenation
  • packet delay
  • packet segmentation
  • synchronous switch


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