A presence server provides presence information to content subscribers via
unicast transmission of the presence information. In the case where the
presence server receives, from a subscriber, a subscription request for
presence information having a relatively large number of subscribers, the
presence server directs the content subscriber to a multicast
transmission channel. The content subscriber, in turn, accesses the
presence information via the multicast transmission channel. By directing
content subscribers toward the multicast transmission channel, the
presence server conserves connection resources associated with the
presence system, thereby allowing the presence system to distribute
presence information with a relatively high level of speed and
efficiency. Furthermore, by directing content subscribers toward the
multicast transmission channel, the presence server minimizes the costs
associated with adding new subscribers to the presence system.