Type-of-Service Routing in Datagram Delivery Systems

The Internet is expected to support various services, including best-eeort services and guaranteed services. For best-eeort services, we propose a new approach to achieving type-of-service (TOS) with adaptive next-hop routing. We consider two traac classes, namely delay-sensitive and throughput-sensitive. In routing protocols such as OSPF and integrated IS-IS, each node has a diierent next-hop for each destination and TOS. Traditionally, each node has a single FCFS queue for each outgoing link, and the next-hops are computed using link measurements. In our approach, we attempt to isolate the two traac classes by using two FCFS queues for each outgoing link, one for each TOS; the link is shared cyclicly between the two TOS queues. The next-hops for the delay-sensitive traac adapts to link delays of that traac. The next-hops for the throughput-sensitive traac adapts to overall link utilizations. We compare our approach with the traditional approach using discrete-event simulation and Liapunov analysis (for stability of routes). The proposed approach ooers lower end-to-end delay to the delay-sensitive traac. A related property is that the routes for the delay-sensitive traac are more stable, i.e. less oscillations. An unexpected property is that the overall end-to-end delay is lower; this is because the link utilization metric makes the throughput-sensitive traac move away to under-utilized routes, thus isolating the two traac classes and yielding a better overall network performance.