Are alterations needed to the IP multicast service model?

Deering's model of Internet group communication, in spite of its simplicity and elegance, imposes limits on the complete development of IP multicast, due either to the profusion of contradictory requirements of applications, or to the reduced support provided by the network core for technical or economic reasons. Even if some of these difficulties may be resolved at the transport or application layers, thus remaining outside the scope of the present model, there also appear defects within this model, mainly due to inter-domain routing, involving address management, to QoS insensitivity and to loss of functionality. The recognition of these defects has already led to the solution presented by the MASC/BGMP project, which involves a transition from the present model. However there are many who argue that the success of unicast applications in TCP/IP will only be repeated in multicast applications through the use of much simpler solutions than the existing ones, or by including greater intelligence in the network interior. With this in mind, we analyse here the proposals RAMA and XCAST, which may be seen to demonstrate greater simplicity. We also look at AIM, designed for organising receivers into subgroups with similar interests. Leveraging Internet group applications will certainly involve one or other, or even both, of these approaches.