Per-flow signalling extension across DiffServ domains

摘要

This paper describes a framework devised to extend per-flow admission control operation across Differentiated Services domains. Although the specific case of interoperability with RSVP is under discussion, our proposal can be easily adapted to other hop-by-hop signalling protocols. In our framework, DiffServ border routers accomplish three tasks. First, during the set-up phase, flows are mapped onto PHB groups on the basis of their QoS and traffic specifications. Second, signalling packets are tunnelled into IP packets marked as "probes", where the "probe" marking is a DCSP value associated to the considered PHB Group. Third, when the flow set-up is complete, flow data packets are marked as "data". The probe/data marking is built upon the Assured Forwarding PHB specification of DiffServ. QoS provisioning is achieved by tuning, within the DiffServ core routers, the dropping rates of AF-marked packets. Our approach provides a scalable solution to determine the decision of accepting/rejecting a transmission request with specified QoS requirements into the network, provisioning a per-flow call blocking service that spans heterogeneous IP domains.