Bandwidth for High Speed Networks

Such a scheme cannot hope to achieve the nearly

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Unformatted text preview: ection 2. Such a scheme cannot hope to achieve the nearly-perfect levels of fairness obtained by Fair Queueing and other sophisticated and stateful queueing algorithms. However, our interest is not in perfection, but only in obtaining reasonable approximations to the fair bandwidth allocations. We derive a worst-case bound for the performance of this algorithm in an idealized setting. This bound is presented in Section 2. This worst-case analysis does not give an adequate guide to the typical functioning of CSFQ. In Section 3 we present results from simulation experiments to illustrate the performance of our approach and to compare it to several other schemes: DRR a variant of Fair Queueing, FRED, RED, and FIFO. We also discuss, therein, the relative mechanistic complexities of these approaches. The rst 3 sections of the paper are narrowly focussed on the details of the mechanism and its performance both absolute and relative, with the need for such a mechanism taken for granted. In Section 4 we return to the basic question of why fair allocations are relevant to congestion control. Allocating bandwidth fairly is one way to address what we call the unfriendly ow problem; we also discuss an alternate approach to addressing this problem, the identi cation approach as described in 8 . We conclude with a summary in Section 5. A longer version of this paper, containing proofs of the theoretical results as well as more complete pseudocode, can be found at http: www.cs.cmu.edu ~isto ica csfq. 2 Core-Stateless Fair Queueing CSFQ In this section, we propose an architecture that approximates the service provided by an island of Fair Queueing routers, but has a much lower complexity in the core routers. The architecture has two key aspects. First, to avoid maintaining per ow state at each router, we use a distributed 2 By island we mean a contiguous portion of the network, with well-de ned interior and edges. 3 Obviously these core routers keep some state, but none of it is per- ow state, so when we say stateless" we are refer...
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This document was uploaded on 03/04/2014 for the course ENG 531 at Rice.

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