Performance models for noahnet

Noahnet is an experimental flood local area network with features such as high reliability and high performance. Noahnet uses a randomly connected graph topology with four to five interconnections per node and a flooding protocol to route messages. The purpose of this paper is to present two analytical performance models which we have designed to understand the load-throughput behavior of Noahnet. Both models assume slotted Noahnet operation and also assume that if k messages attempt transmission in a slot, the network gets divided into k partitions of arbitrary sizes - one partition for each message. First, we show that the average number of successful messages in a slot given k attempted transmissions is (M - k)/(N - 1), where N is the number of nodes in the network and M is the number of nodes out of N that participate in the flooding of A; messages. This is an interesting result and is used in both models to derive the load-throughput equations. Each model is then presented using a set of assumptions, derivations of load-throughput equations, a set of plots, and the discussion of results. Models one and two differ in the way they account for retransmissions. Model two helps study the effect of retransmission probability on the performance of the network. The results from these models suggest that the maximum throughput of Noahnet is always less than one message per slot. Also the network is unstable in the sense that the throughput increases with the load only up to a certain threshold value of load; beyond that the throughput starts decreasing with the load. Model two suggests that Noahnet is essentially a contention system, and to get the maximum throughput, the load should be such as to give the optimal contention.