Class-based Multicast Routing in Inter-domain Scenarios

Maria J Nicolau*, António Costa**, Joaquim Macedo**, Alexandre Santos**

Universidade do Minho
Escola de Engenharia
Departamento de Sistemas de Informação*
Departamento de Informática**
4710-057 Braga, Portugal

Tel.: +351 253 604430
Fax.: +351 253 604471
E-mail: joao (at), costa (at), macedo (at), alex (at)


DiffServ like domains bring new challenges to QoS multicast routing simply by changing the focus from individual flows to classes of flows. Packets are marked at edge routers and receive differentiated treatment according to the class and not the flow that they belong to. DiffServ became therefore adverse to multicast, as packet replication inside domain may require classification and remarking functions not present in core nodes.

At inter-domain level, DiffServ and non-DiffServ domains are connected between each other, making it more difficult to address QoS multicast in an end-to-end perspective. Classes of service have no meaning in certain links of a full inter-domain path. While the problem is not new and was already previously pointed out there are no real efforts to bring multicast back to a class-of-service domain without compromising its model of operation.

In this article we present an innovative multicast QoS routing strategy, clearly designed for the new class-of-service paradigm. Solution is based upon the construction of multiple trees, one per class of service available, while still allowing receivers to shift for source specific trees in its own class of service.

The strategy is presented in a full end-to-end perspective. Intra-domain trees use different paths and also help traffic differentiation. Intra-domain receivers are allowed to shift from shared tree to an adequate class of service source tree.

At inter-domain level, each class of service inter-domain tree branche is accomplished by means of an improved path probing strategy.

This paper presents a new strategy , and associated protocols, for constructing several multicast and directed distribution trees, one per class of service within each source based multicast group. The new strategy and associated protocols, enabling also the construction of directed shared trees, are then simulated using NS-2 platform. Simulation results are analysed and compared with other multicast routing solutions, both at intra and inter-domain levels.

(Annals of Telecommunications Vol. 63(11-12) - Special Issue on Inter-Domain Routing and QoS over Heterogeneous Networks , Springer Paris, 2008)