Dynamic Configuration of Conferencing Applications using Pattern-Matching Multicast

Multimedia conferencing systems are usually large, complex software systems. We describe a local control architecture and communication protocols called pattern-matching multicast (PMM) that allow media agents, controllers and auxiliary applications such as media recorders and management proxies to be tied together into a single conference application. Unlike other systems, control of a single conference can be shared between several controllers. Each medium can be handled by one or more independent media agents. Parts of the system have been implemented using an IP-multicast-based audio conferencing tool (NeVoT). The communicating applications disseminate state and control information through a distributor. The distributor mainly limits distribution of messages based on expressed interest of other applications, thus implementing an application-level, receiver-driven local multicast. It also automatically starts applications as needed. The same inter-application protocol was also implemented using IP multicast restricted to the local host and can be based on other inter-process messaging services such as ToolTalk.