Patent ID: 8363644

Claim:
A method for use in a communication system implemented over a network comprising a plurality of user nodes, each being associated with a respective presence status indicating an availability of the user node for communication within the communication system; the method comprising, at each of a first one or more of the user nodes: maintaining a contact list specifying a selection of contacts from said plurality of user nodes; associating a presence update priority level with each of the contacts, the presence update priority level relating to an estimated likelihood of communication between the first user node and the respective contact; and transmitting a presence message to each of a plurality of said contacts in dependence on the respective presence update priority level, each of said presence messages comprising at least one of: a request for the presence status of the contact, and a notification of the presence status of the first user node, wherein the transmission of said presence messages comprises transmitting a respective number of presence messages to each of said plurality of contacts over a portion of time, the numbers being determined having relative ratios dependent on the respective presence update priority level for each contact.