Protection interworking for SDH networks

The design of survivable and highly available SDH (synchronous digital hierarchy) telecommunications networks is becoming increasingly important. This is due to the continuing increase in the capacity of line systems, so that a single failure potentially results in the loss of a greater volume of traffic, and the increase in the demand from users such as banks and businesses for highly reliable services. The installation of protection devices improves the reliability of a network at the cost of the need to provide extra capacity for the protection paths and the introduction of extra equipment and management complexity. Protection interworking, where more than one protection scheme operates on a single connection across a telecommunications network, is of current interest owing to the drive for more and more reliable networks, the continuing increase in complexity of single networks and the growth in interconnection of networks belonging to different operators. Used wisely, protection interworking will ensure network survivability, improve connection availability and also simplify protection management. This paper examines how protection mechanisms can be made to interwork in the most effective way, with particular reference to matched node interconnection of MS-SPRings