Multicasting is the most cost-effective means of delivering streaming media over the Internet, but its deployment has been limited by a number of technical and business problems. Within the last year, there have been several efforts to address these problems in the context of multicast one-to-many broadcasting. This is part of the general abandonment of the "Swiss Army knife" approach, where one multicast model was supposed to fit all possible uses, for multicast models tuned for specific applications.

Single Source Multicast (SSM) uses the Internet Group Management Protocol (IGMP) version 3 and a subset of the capabilities of Protocol Independent Multicast - Sparse Mode (or PIM-SM) to implement a broadcast model where receivers know the IP address of the source (from, say, a web page), and join a specific (Source,Group) pair. This, besides greatly simplifying the operation of the protocol, means that multicast transmissions can be limited to specific IP addresses, and makes it harder to spoof or interrupt multicast transmissions. Other recent innovations include a tailoring of the Real Time Control Protocol to scale to large audience sizes, and the spread of multicast friendly Internet exchanges. In my talk I will describe the SSM protocol, its advantages, and the other work leading to a workable business model for multicast broadcasting.