VIRTUAL PATH GROUP PROTECTION SWITCHING - A METHOD FOR FAST ATM NETWORK SURVIVABILITY

A telecommunications network often has survivability capabilities to r estore service following the occurrence of various service-affecting d efects. To ensure high reliability over a wide range of services the n etwork must be able to restore service very quickly, on the order of 6 0 to 200 ms. This requirement can place extreme and costly processing demands on network elements (NEs). Many different survivability techni ques are possible depending on an application's cost, service, and per formance requirements. Furthermore, networks are now being developed b ased on asynchronous transfer mode (ATM) technology and carried within a synchronous digital hierarchylsynchronous optical network (SDH/SONE T) physical layer. In these networks, the existing physical-layer prot ection switching capabilities (for example, SDH/SONET line or path pro tection switching) cannot detect ATM-specific defects (such as loss of ATM connection continuity) and thus cannot protect against them. Whil e protection switching of individual ATM virtual connections (virtual path [VP] or virtual channel [VC]) could be added to accommodate ATM-s pecific defects, such a large-scale defect as a facility failure will cause a fault on each of hundreds or even thousands of separate ATM co nnections and thus will require as many simultaneous and independent r estoration operations. The virtual path group (VPG) protection switchi ng technique described in this paper offers both fast restoration (on the order of 60 ms) and minimum processing. This technique, useful in a broad range of ATM networking applications, provides high-performanc e network protection largely consistent with established ATM standards . It forms a basis for emerging ATM network protection standards, and it will provide leading-edge network survivability features to future Lucent Technologies ATM solutions.