The utility of feedback in layered multicast congestion control

  • Authors:
  • Sergey Gorinsky;Harrick Vin

  • Affiliations:
  • Laboratory for Advanced Systems Research, Department of Computer Sciences, The University of Texas at Austin, Taylor Hall 2.124, Austin, TX;Laboratory for Advanced Systems Research, Department of Computer Sciences, The University of Texas at Austin, Taylor Hall 2.124, Austin, TX

  • Venue:
  • NOSSDAV '01 Proceedings of the 11th international workshop on Network and operating systems support for digital audio and video
  • Year:
  • 2001

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Abstract

Layered multicast is a common approach for dissemination of audio and video in heterogeneous network environments. Layered multicast schemes can be classified into two categories - feedback-based and feedback-free - depending on whether or not the scheme delivers feedback to the sender of the multicast session. Advocates of feedback-based schemes claim that feedback is necessary to match the heterogeneous receiver capabilities efficiently. Supporters of feedback-free schemes believe that feedback introduces significant complexity and that a moderate amount of additional layers can balance any benefit the feedback provides. Surprisingly, there has been no systematic evaluation of these claims. This paper provides a quantitative comparison of feedback-based and feedback-free layered multicast schemes with respect to aligning the provided service to the capabilities of heterogeneous receivers. We discover realistic scenarios when feedback-free schemes require a very large number of additional layers to match the performance of feedback-based schemes. Our studies also demonstrate that a light-weight feedback-based scheme can offer substantial improvement in performance over feedback-free schemes and can closely approximate the efficiency achieved by the optimal feedback-based scheme.