IP MULTICASTING OVER ATM NETWORKS

The Internet protocol (IF) multicast model involves a combination of i ntrasubnet and intersubnet multicast mechanisms. Technologies supporti ng a given subnet are expected to have native mechanisms for supportin g intrasubnet forwarding of pacets sent to multicast destinations, Mul ticast routers attach to subnets and provide intersubnet forwarding of multicast packets, using interdomain multicast Pouting protocols deve loped by the Internet Engineering Task Force (IETF), Unfortunately, AT M networks based on UNI 3.0 or UNI 3.1 signaling service do not provid e the native multicast support expected by IF. This has led the IETF t o develop the ''MARS model''-a fairly complex mechanism for emulating intrasubnet multicast support required when running IP's over ATM's. T his paper takes a high level look at the IP multicast service, examine s the limitations of the ATM point-to-multipoint virtual channel servi ce, and describes the major architectural points of the MARS model.