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In this paper, we develop a concise performance model of partial packet discard (PPD) and early packet discard (EPD) schemes in ATM switches. We study the performance of PPD and EPD with heterogeneous traffic sources. The sources included Poisson, and ON-OFF with long-tailed sojourn time distribution, which is approximated by a hyperexponential distribution. The fairness of EPD is investigated. We automatically generate and numerically solve the underlying Markov chain using a high-level graphical paradigm known as the stochastic reward net. Our numerical results reveal that: (1) the benefit of PPD and EPD is not significant when the queuing system is underloaded with Poisson sources; (2) PPD and EPD can increase the goodput when the system is overloaded or loaded with ON-OFF sources; (3) in All Poisson case, PPD and EPD provide nearly fair service to the sources; (4) the ON-OFF source gets higher goodput than the Poisson source. Because the burstiness of a source will be alleviated by the statistical multiplexing of ATM switches, the ON-OFF source may be viewed as the source that just enters the network, and the Poisson source may be viewed as the source being far away from the network node we are considering and has been regulated and smoothed by the switches it traversed. Therefore, the queuing system with EPD algorithm gives a higher goodput to the sources near it. And the sources far away from the system will have lower goodput. One of our principal conclusions is that per-VC-based scheme is not needed at the core of large ATM networks because the traffic is less bursty at the core of the networks and PPD and EPD are fair under this kind of environment. A per-VC-based scheme may be used at the edge of the ATM cloud. Such a configuration can make the core of the ATM network work at high speed.

In this paper, we develop performance models of the Broadcast and Unkn own Server (BUS) in the LANE. The traffic on the BUS is divided into two classes: the broadcast and multicast traffic, and the unicast relay flow. The broadcast and multicast traffic is assumed to form a Markov Modulated Poisson Process (MMPP). The traffic for a particular unicast relay flow is an MMPP as well. However, the number of active unicast relay flows sojourning on the BUS is determined by a tandem queueing system, where the flow arrival process is Poisson, the address resolution delay is exponentially distributed, and the connection setup delay is three-stage Erlang distributed. The size of data frames in traffic flows is a random variable with three possible values: short, medium, and large. In order to deal with the intractability (i.e., largeness and stiffness) of the underlying Markov chain, a hierarchical model is used to decompose the system. With the help of Stochastic Petri Net Package (SPNP), a software package for the automated generation and solution of Markovian stochastic systems, and the decomposition method, we study the performance of the BUS module under different loads. We also investigate the effect of address resolution delay and connection setup delay on the performance of the BUS.

The performance of prioritized distributed queue dual bus (DQDB) metropolitan area network (MAN) under bursty traffic environment is studied in this article. The tagged node model is adopted to simplify the analysis. The processes of the packet arrivals to the tagged node, the empty-slot pattern from the upstream, and the request pattern from the downstream are assumed to be Markov Modulated Poisson Processes, a more general and appropriate model to capture the bursty characteristics existing in the traffic flows in high-speed networks. A stochastic reward nets model for the prioritized DQDB MAN is presented. With the help of the stochastic petri net package developed in Duke University, the steady state and as well as the transient behavior of packet loss ratio of tagged node are investigated. The influence of the burstiness of the empty-slot pattern, packet arrival and request pattern on the tagged node's performance are examined.