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

of the scheme is unclear, and is expected to be lower because of the conservative
parameter settings.
Researchers at University of California at Irvine (UCI) suggested a solution to the
problems of EPRCA through a scheme they developed called \Adaptive Proportional
Rate Control" [57]. Essentially, they suggested that the queue growth rate be used
as the load indicator instead of the queue length. The change in the queue length
is noted down after processing, say, K cells. The overload is indicated if the queue
length increases.
However, this approach still su ers from the defect that the metric gives no in-
formation when the queue lengths are close to zero (underutilization). Basically, the
problem is that the queue length information needs to be combined with the ABR
capacity and ABR utilization to get a full picture of the congestion situation at the
switch.
4.7 CAPC2
In October 1994, Barnhart from Hughes Systems proposed a scheme called \Con-
gestion Avoidance using Proportional Control (CAPC)[10]."
4.7.1 Key Techniques
This scheme used some of the concepts developed in the OSU scheme and used
a phase-locked loop style lter in the algorithm. In this scheme, as in OSU scheme
(described later in this dissertation), the switches set a target utilization parameter
slightly below 1. This is the ABR capacity utilization the scheme aims to achieve.
As in this OSU scheme, the switches measure the input rate and load factor z (which
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