Multicast Addressing

Multicast addressing is a focused broadcast capability implemented at the hardware and operating system level. In the same way that the Rendezvous daemon filters out unwanted messages based on service groups, multicast hardware and operating system features filter out unwanted messages based on multicast addresses.

When no broadcast messages are present on the service, multicast filtering (implemented in network interface hardware) can be more efficient than service group filtering (implemented in software). However, transports that specify multicast addressing still receive broadcast messages, so combining broadcast and multicast traffic on the same service can defeat the efficiency gain of multicast addressing.

Rendezvous software supports multicast addressing only when the operating system supports it. If the operating system does not support it, and you specify a multicast address in the network argument, then transport creation calls produce an error status (TIBRV_NETWORK_NOT_FOUND).