Virtual path group protection switching-A method for fast ATM network survivability

Abstract

A telecommunications network often has survivability capabilities to restore service following the occurrence of various service-affecting defects. To ensure high reliability over a wide range of services, the network must be able to restore service very quickly, on the order of 60 to 200 ms. This requirement can place extreme and costly processing demands on network elements (NEs). Many different survivability techniques are possible depending on an application's cost, service, and performance requirements. Furthermore, networks are now being developed based on asynchronous transfer mode (ATM) technology and carried within a synchronous digital hierarchy/synchronous optical network (SDH/SONET) physical layer. In these networks, the existing physical-layer protection switching capabilities (for example, SDH/SONET line or path protection switching) cannot detect ATM-specific defects (such as loss of ATM connection continuity) and thus cannot protect against them. While protection switching of individual ATM virtual connections (virtual path [VP] or virtual channel [VC]) could be added to accommodate ATM-specific defects, such a large-scale defect as a facility failure will cause a fault on each of hundreds or even thousands of separate ATM connections and thus will require as many simultaneous and independent restoration operations. The virtual path group (VPG) protection switching 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-performance 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.