Data distribution system

摘要

A data distribution system used for videoconferencing and the like comprises a plurality of Points of Presence (POPs) (4a-4d) on a global network (2). Each POP includes a control device (6) and at least one processing device (8). Clients (16) are sent a cryptic string such as a URI by a session manager (12), which they access to join a conference session at a POP nearest to the client. Clients are registered in a database (14). The control device authenticates the client and then assigns it to one of the processing devices in the POP. Clients are associated with multicast groups, and the processing devices multicast data received from clients to all other group members. Processing devices are registered to a control device in their own POP and to another control device in a different POP for redundancy in case a control device becomes unavailable (e.g. 6c).