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

inside the ATM network can be controlled with the ABR service, in a heterogeneous
network environment, the cells belonging to TCP streams may queue at the edge
routers, i.e., at the entrance to the ATM network. Some form of end-to-end ow
control involving the TCP end system is still necessary to avoid cell loss under such
conditions.
In section 8.16.2 and 8.18.5, we studied the e ect of the VBR background tra c
patterns on the bu er requirements for TCP over ABR. The e ect of the background
tra cistocreatevariation in ABR capacity. The switch algorithm needs to be robust
to handle the variation in ABR capacity (due to VBR) and in ABR demand (due
to TCP dynamics). We motivate three enhancements to the ERICA+ scheme which
reduce the e ect of the variation and allow the convergence of the ABR queues,
without compromising on e ciency. We then use a model of several multiplexed
MPEG-2 video sources over VBR. In this e ort, we also brie y survey VBR video
modeling techniques, the MPEG-2 over ATM approach, and propose a model for
MPEG-2 video over VBR which incorporates the long-range dependence property in
compressed video. Compressed video sources exhibit long-range dependence in the
tra c patterns they generate. We verify that the ERICA+ algorithm is robust to the
variation introduced by such background tra c and can control the ABR queues.
Finally, in section 8.19, we refer to a related study of the e ect of bursty appli-
cations (such as the World Wide Web application) running on top of TCP. Bursty
applications can potentially cause unbounded ABR queues since they can use open
TCP windows to send bursts of data. However, Vandalore et al [79] show that since
ABR switches respond to load increases, if the aggregate load increases as a function
of the number of applications, then the switch will assign lower rates to sources and
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