Whether that content consists of employee training courses, shareholder meeting reports or product announcements, using multicast technology saves bandwidth and server load. Not a separate backbone, the M-Bone is an address space laid on the existing backbones that operate the Internet and intranets. The M-Bone was realized at the outset of IP address classes, and space was set aside for experimental use. Multicast sessions are assigned a multicast group ID, which in essence is an IP address within the Class D range. A host may join as many multicast groups as needed and is able to leave at any time.
Physical location is irrelevant, as is the number of members in a group.
It's up to the multicast routers to distribute the packets to all members of the group that are downstream.