Analysis of congestion onset thresholds for CCITT SS7 networks

Congestion controls are a key factor in achieving the required robust performance of common channel signalling networks in the face of partial network failures and extreme traffic loads, especially as networks become large and carry high traffic volume. The CCITT recommendations define a number of types of congestion control, and the parameters of the controls must be well set in order to ensure their efficacy under transient and sustained signalling network overload. The objective of this paper is to present a modelling and analysis approach to the determination of the level 2 queue congestion onset threshold, which is central to the operation of the MTP level 3 congestion controls. A queueing model is presented for the transient analysis of the level 2 transmit queue during a changeover procedure, leading to a method of setting the first onset threshold consistent with criteria defined in the CCITT recommendations.