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
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...
View Full Document
- Fall '10
- Eugene Ng
- Scheduling algorithm, Round-robin scheduling, Scheduling algorithms, Ow, Fair queuing, ows