Traffic Management for the Available Bit Rate (ABR) Service in ...

hand side of the equation is the sum of the rate of growth of the ABR queue ( dqa(t)
dt )
and the capacity (Ca(t)) scaled by the utilization factor ( a(t)). In other words, the
ABR demand directly a ects the ABR utilization and the rate of growth of the ABR
queue.
We desire that the system calculate and feedback rate assignments ri(t) which
satisfy a desired set of goals. Since the goals are many, we elaborate the goals later in
chapter 3. More generally, the problem we consider is the design of tra c management
mechanisms for the ABR service. We consider ve aspects of this problem in this
dissertation. Firstly, the service requires a mechanism to carry rate feedback from
the switches to the sources. We also design switch algorithms which calculate the
rate allocations ri(t) to satisfy a given set of goals. Secondly, we design a set of
source mechanisms which respond to feedback, and perform control when feedback is
disrupted or is stale. Thirdly, we validate the performance of the service for various
ABR and VBR demand patterns (di(t) and dv(t)). Speci cally, we study the case of
Internet tra c over ABR. Fourthly, we consider the switch design issues for a speci c
ABR framework option called the \Virtual Source/Virtual Destination" option. The
detailed problem speci cations and goals are considered in the respective portions of
the dissertation.
Our general methodology for tackling this problem is the use of experimentation
and simulation techniques, rather than rigorous mathematical analysis. This tech-
nique helps us build models which are closer to the real-world systems than math-
ematical models. However, we rely on simple analytical tools and techniques (such
as metric design, and correlation of feedback with control) to ensure stability ofthe
designed system.
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