Bandwidth for High Speed Networks

Rlm is such an algorithm9 third some users will cheat

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Unformatted text preview: ithms, and 2 these algorithms are homogeneous or roughly equivalent in that they produce similar bandwidth allocations if used in similar circumstances. In particular, assumption 2 requires, in the language of 8 , that all ows are TCPfriendly.8 The assumption of universal cooperation can be violated in three general ways. First, some applications are unresponsive in that they don't implement any congestion control algorithms at all. Most of the early multimedia and multicast applications, like vat, nv, vic, wb and RealAudio fall into this category. Second, some applications use congestion control algorithms that, while responsive, are not TCP-friendly. RLM is such an algorithm.9 Third, some users will cheat and use a non-TCP congestion control algorithm to get more bandwidth. An example of this would be using a modi ed form of TCP with, for instance, a larger initial window and window opening constants. Each of these forms of noncooperation can have a signi cant negative impact on the performance obtained by cooperating ows. At present, we do not yet know how widespread noncooperation will be, and thus cannot assess the level of harm it will cause. However, in lieu of more solid evidence that noncooperation will not be a problem, it seems unsound to base the Internet's congestion control paradigm on the assumption of universal cooperation. We therefore started this paper with the fundamental assumption that one needs to deal with the problem of unfriendly ows. 8 Actually, the term TCP-friendly in 8 means that their arrival rate does not exceed that of any TCP connection in the same circumstances." Here we use it to mean that the arrival rates are roughly comparable, a property that should be more precisely called TCP-equivalent. We blur the distinction between TCP-friendly and TCP-equivalent to avoid an overly unwieldy set of terms in this short overview. However, we think the distinction may be rendered moot since it is unlikely that congestion control algorithms that are not TCP-equivalent but are TCP-friendly i.e., they get much less than their fare share will be widely deployed. 9 Although our data in Section 3.3 showed RLM receiving less than its fair share, when we change the simulat...
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This document was uploaded on 03/04/2014 for the course ENG 531 at Rice.

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