A class of self-healing ring architectures for SONET network applications

A class of SONET-based self-healing ring (SHR) architectures and associated control schemes are reviewed. It is shown that the cost and capacity tradeoffs between bidirectional SHRs (B-SHRs) and unidirectional SHRs (U-SHRs) depend strongly upon the application, the network size and the demand pattern. An analysis of the impact on the SONET standard suggests that using automatic protection switching (APS) schemes with SONET SHR architectures requires a change of currently standardized SONET K1 and K2 overhead byte definitions and functionality. Alternatively, a simple distributed control scheme using path AIS avoids a change of the SONET standard in terms of K1 and K2 operations, and thus can be deployed on a timely basis and may ease intervendor compatibility problems. The selection of appropriate SONET SHR architectures depends upon the operating telephone companies' economic analysis, emphases on multivendor environment, SHR implementation time frame, and standards progress on making the change to support a bidirectional ring architecture. >