A queueing model for PCEP (Path Computation Element Protocol)

Path computation elements (PCE’s) are used to compute end-to-end paths across multiple areas. Multiple PCE’s may be dedicated to each area to provide sufficient path computation capacity and redundancy. An open problem is which PCE should be chosen to send the path computation request to, that may be a non trivial problem if PCE’s have uneven processing capacities. This paper presents a product form queueing model to estimate the latencies in path computation while accounting for the arrival rate of path computation requests. The model is used to find the PCE selection policy to minimize the average expected latencies in path computation. The model is validated against two simulation benchmarks obtained using OPNET, i.e., a network of queues and the multi protocol label switching with traffic engineering (MPLSTE) network running the PCE communication protocol (PCEP). The study shows that the use of product form yields approximations that are up to 15% at practical offered loads. Moreover, the PCE selection policy derived under the product form assumption is showed to be effective in minimizing the overall expected latencies in path computation.