A study of the path availability improvements in a large network for various route diversity protection strategies, using failure event simulation

This study was motivated by the need to understand the way in which protection equipment capable of rerouting traffic lost after a section or route failure around that failure improves the path availability across a trunk network. Since no assumptions are made about bit rates in the results, then they may equally be applied not only to trunk networks but to regional and even local networks. Particular reference is made to SONET or SDH networks. It is arguable that PSTN switches such as System X are capable of rerouting traffic at the 2 mB/s level around failed links. At the local and regional level, this may be a suitable mechanism for PSTN traffic, but trunk traffic capacities are so high (64 to 256 by 2 Mb/s) and since the need is for service restoration in the order of a few seconds at most, trunk level protection needs to be done at 34 Mb/s or higher using dedicated equipment. The background, basic theory and computer model results for various route failure protection networks and protection strategies have been given. Results show that the performance of a protection system are most affected by the failure rates (particularly that of routes), the repair rates, the amount of transmission plant dedicated to protection, and the mean valence of network nodes