Computer Laboratory

Technical reports

An estimator of forward and backward delay for multipath transport

Fei Song, Hongke Zhang, Sidong Zhang, Fernando Ramos, Jon Crowcroft

March 2009, 16 pages

Abstract

Multipath transport protocols require awareness of the capability of different paths being used for transmission. It is well known that round trip time (RTT) can be used to estimate retransmission timeout with reasonable accuracy. However, using RTT to evaluate the delay of forward or backward paths is not always suitable. In fact, these paths are usually dissimilar, and therefore the packet delay can be significantly different in each direction.

We propose a forward and backward delay estimator that aims to solve this problem. Based on the results of the estimator, a new retransmission heuristic mechanism for multipath transport is proposed. With this same technique we also build two other heuristics: A bottleneck bandwidth estimator and a shared congestion detector. These help the sender to choose the high bandwidth path in retransmission and ensure TCP-friendliness in multipath transport, respectively.

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BibTeX record

@TechReport{UCAM-CL-TR-747,
  author =	 {Song, Fei and Zhang, Hongke and Zhang, Sidong and Ramos,
          	  Fernando and Crowcroft, Jon},
  title = 	 {{An estimator of forward and backward delay for multipath
         	   transport}},
  year = 	 2009,
  month = 	 mar,
  url = 	 {http://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-747.pdf},
  institution =  {University of Cambridge, Computer Laboratory},
  number = 	 {UCAM-CL-TR-747}
}