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

However, certain problems need to be solved before this idea can be used e ec-
tively. First, the maximum VC rate oscillates excessively leading to transient instabil-
ities in the behavior. This problem can be tackled by smoothing the maximum rate,
ltering out the short-term variations. Second, in some situations, the maximum rate
does not converge rapidly to the fairshare, again compromising fair behavior. The
authors address this by using a reduction factor which is a function of the degree of
congestion in the switch.
DMRCA uses two thresholds QT and DQT on the queue length for congestion
detection. The switch also monitors the maximum rate MAX of all connections
arriving at the switch, as well as the VC number of the corresponding connection,
MAX VC.
The algorithm smoothes excessive oscillations in MAX using exponential averag-
ing to calculate an adjusted maximum rate, as:
A MAX =(1; Alpha) A MAX + Alpha MAX
The averaging factor, Alpha is typically 1/16. The implementation is as follows:
if( RMCell; >CCR Beta MAX) f
A MAX =(1; Alpha) A MAX + Alpha RMCell; >CCR
g
This implementation avoids the need for measurement of MAX over a measure-
ment interval. MAX increases when some VC other than MAX VC observes that
its rate is larger than MAX. MAX decreases when MAX VC updates MAX based
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