Evaluation of message delays at packet switching nodes serving multiple classes with random number of packets and different packet lengths

Packet switching nodes multiplex messages from a variety of sources. For example, there may be message inputs from other packet-switching nodes, individual user terminals and host computers. Achieving message delay tradeoffs among the various users´ classes is an important aspect of engineering a packet switch. This paper presents a methodology to find average message system times for messages having random number of packets. This methodology allows us to analyze the system in which each class messages have any number of packets. It also examines the effect of using different packet lengths on throughput. An expression for the waiting time experienced by the i^th packet awaiting transmission is presented. The waiting time expression derived by Daigle (1995), is generalized for messages having random number of packets with different packet lengths then the overall average message delays can be computed easily through a computer program