Edge-Based Fault Detection in a DiffServ Network

The phenomenal growth of QoS-aware applications over the Internet has accelerated the development of key technologies such as Differentiated Services (DiffServ). Although QoS is provided through class-based service differentiation, the aspect of fault tolerance is not addressed in the DiffServ architecture. For traditional IP networks, the underlying link state protocol provides fault detection and recovery. However, for QoS sensitive flows, the recovery times of such protocols may not be adequate. Although such a problem may be solved through fine grain HELLO timers, the underlying core routers may not be able to tolerate the additional CPU and bandwidth burden. The edge-based intelligence of the DiffServ domain represents a unique opportunity to improve the fault detection capability of the link state protocol. In this paper, we propose a hybrid scheme whereby heartbeat packets are used to detect possible faults coupled with a temporary fine grain HELLO interval for fault location and possible recovery. We analyze our scheme through extensive simulation studies and we examine the tradeoffs and benefits of our scheme.