The communication network of the near future is going to be based on Asynchronous
Transfer Mode (ATM) which has widely been accepted by equipment vendors and
service providers. Statistical multiplexing technique, high transmission speed and
multimedia services render traditional approaches to network protocol and control
ineffective. The ATM technology is tailored to support data, voice and video traffic
using a common 53 byte fixed length cell based format with connection oriented
routing.
Traffic sources in A TM network such as coded video and bulk data
transfer are bursty. These sources generate cells at a near-peak rate during their active
period and generate few cells during relatively long inactive period. Severe network
congestion might occur as a consequence of this dynamic nature of bursty traffic.
Even though Call Admission Control (CAC) is appropriately carried out for deciding
acceptance of a new call, Quality of Service (QOS) may be beyond the requirement
limits as bursty traffic are piled up. So, priority control, in which traffic stream are
classified into several classes according to their QOS requirements and transferred
according to their priorities, becomes an important research issue in ATM network. There are basically two kinds of priority management schemes: time
priority scheme that gives higher priority to services requiring short delay time and
the space priority scheme that gives high priority cells requiring small cell loss ratio.
The possible drawbacks of these time and space priority schemes are the processing
overhead required for monitoring cells for priority change, especially in the case of
time priority schemes. Also, each arriving cell needs to be time stamped. The
drawback of the space priority scheme lies in the fact that buffer management
complexity increases when the buffer size becomes large because cell sequence
preservation requires a more complicated buffer management logic.
In this thesis, a Mixed Priority Queueing or MPQ scheme is proposed
which includes three distinct strategies for priority control method -- buffer
partitioning, allocation of cells into the buffer and service discipline. The MPQ
scheme is, by nature, a non-fixed priority method in which delay times and loss
probabilities of each service class are taken into account and both delay times and
loss probabilities can be controlled with less dependency compared with the fixed
priority method, where priority grant rule is fixed according to the service class, and
the priority is always given to the highest class cell among cells existing in the
buffer. The proposed priority control is executed independently at each switching
node as a local buffer management. Buffer partitioning is applied to overcome the
weakness of the single buffer
