| Summary: | 碩士 === 國立交通大學 === 資訊工程研究所 === 81 === In this thesis, a QOS driven congestion control method is
proposed. As we already know, Asynchronous Transfer Mode (ATM)
is expected to be adopted by the CCITT as the switching and
multiplexing method for BISDN. Congestion control in ATM
networks is difficult because of the high link speed, diverse
service requirements, and various characteristics of the
traffic ATM is expected to support. In our method, the QOS is
mainly regarding the maximum delay variance and maximum cell
loss rate. The proposed congestion control method includes
admission control and policing techniques. In the proposed
admission control method, each call with different QOS
requirements will obtain different logical buffer size in the
switch nodes, and therefore, will experience different cell
loss rate. A new coming call request will be admitted by a
switch node if each existed connection plus the new coming one
can tolerate the cell loss rate in the output buffer of the
switch node. Once a call request is admitted, we must monitor
the traffic source to avoid its output overwhelming the network
(policing). In the proposed policing method, we use a
"sleeping leaky bucket" to control the traffic flow, where
cells will enter the network at peak rate if the traffic load
along the designated route is light, and at mean rate if the
traffic load becomes heavy. The simulation results show that
our proposed congestion control method has an expected
performance.
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