TCP-PR: TCP for Persistent Packet Reordering

  • Authors:
  • Stephan Bohacek;João P. Hespanha;Junsoo Lee;Chansook Lim;Katia Obraczka

  • Affiliations:
  • -;-;-;-;-

  • Venue:
  • ICDCS '03 Proceedings of the 23rd International Conference on Distributed Computing Systems
  • Year:
  • 2003

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Abstract

Most standard implementations of TCP perform poorly when packets are reordered.In this paper, wepropose a new version of TCP that maintains highthroughput when reordering occurs and yet, whenpacket reordering does not occur, is friendly to otherversions of TCP.The proposed TCP variant, or TCP-PR,does not rely on duplicate acknowledgements to detecta packet loss.Instead, timers are maintained to keeptrack of how long ago a packet was transmitted.Incase the corresponding acknowledgement has not yetarrived and the elapsed time since the packet was sentis larger than a given threshold, the packet is assumedlost.Because TCP-PR does not rely on duplicateackowledgments, packet reordering (including out-of-orderacknowledgments) has no effect on TCP-PR'sperformance.Through extensive simulations, we show that TCP-PRperforms consistently better than existing mechanismsthat try to make TCP more robust to packet reordering.When the case that packets are not reordered, we verifythat TCP-PR maintains the same throughput as typicalimplementations of TCP (specifically, TCP-SACK) andshares network resources fairly.