Reducing the traffic involved in presence change notification between two networks by using watcher lists in network presence servers

摘要

A presence management system includes: a first presence server that controls a first network; a plurality of presentities that belong to the first network; a second presence server that controls a second network, the second network connected to the first network via a communication channel; and a plurality of watchers belonging to the second network; wherein the first presence server includes: a first watcher list that registers a given presentity under the first network associated with one of the watchers that requests presence information of the given presentity; and an external notification section that sends the presence information of the given presentity to the second presence server, and wherein the second presence server includes: a second watcher list that registers the one of watchers associated with the given presentity; and an internal notification section that sends the presence information to the one of watchers registered correspondingly to the given presentity. Thus, if a watcher and a presentity belong to different LANs (Local Area Network), the need for sending as many messages as the number of watchers to the IP network is eliminated, as the notification is sent only once.