Congestion control in frame relay networks

Congestion Control in Frame Relay Networks has been identified as an area of current research. The literature identifies two forms of congestion control, implicit and explicit. Explicit congestion control is built into the Frame Relay Protocol in the form of the BECN and FECN bits. As Frame Relay is a high throughput packet switching protocol currently being implemented to interconnect LANs across a dispersed geographical area, propagation delay is a factor to consider. This study identifies and investigates the effect of propagation delay on a star connected Frame Relay Network during congestion events. It investigates this using a closed queueing network model with adaptive window control. This model is first validated using Buzen's algorithm and queueing theory. A fixed threshold for the average queue length at the congested node is then used as the statistic of interest. The propagation delay between the source ingress node and the congested node is converted into the same units as the average queue length. This is then ignored, added or subtracted from this threshold on a per virtual circuit basis. The effect on the simulated network is measured and it is found that the maximum normalised power is observed when propagation delay is subtracted from the threshold. The main conclusion of this work is that the propagation delay should be subtracted from the fixed threshold average queue statistic to effect maximum power in the network.