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

congestion control deals with the control of a group of ows sharing a group of net-
work resource. It is possible to design congestion control schemes which essentially
control ows individually at every hop. This makes the problem similar to ow con-
trol. An example of such a design is the hop-by-hop ow-controlled virtual circuit
[64] or credit-based framework proposal for ATM discussed later in the dissertation.
1.4 Tra c Management for the ABR Service
In this dissertation, we shall address the problem of designing tra c management
mechanisms for the ABR service class of ATM networks.
1.4.1 Problem Statement
Tra c management for ABR involves using end-to-end feedback control to match
the variable ABR bandwidth at the network ABR queuing points with the variable
demand of ABR sources. The statement of the abstract control problem(s) is(are) as
follows:
Consider a bottleneck queuing point fed by a set of ABR sources. De ne the
following per-source variables:
di(t) : is the desired demand (rate) of the i th source at time t
ri(t) : is the network-assigned rate of the i th source at time t
T i d : is the propagation delay from the i th source to the bottleneck (T ;
d T i d T +
d ).
De ne the following bottleneck variables:
B : The bu er size at the bottleneck (constant)
C : The total capacity of the bottleneck (constant)
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