Hierarchical Notification Dissemination for IMS Presence Using Network Coordinates

The presence service provides event-based notifications of the status of contacts. Currently duplicate notifications must be sent directly to a set of watchers in unicast messages, putting unneeded strain on outgoing network links of the source node. In this article, we propose an extension to the Session Initiation Protocol (SIP) to distribute notifications through a tree of watchers using network coordinates to build the tree. Our simulation results show traffic costs halved by using the extension without significantly adding delay.