| A 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 the outgoing network links of the source node. 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.;Simulations were performed using variations of the input parameters to test the scalability, reliability, notification delay, and load on the network under different conditions. The results show traffic costs halved by using the extension without significantly adding delay, even as additional users are added to the simulation with the same set of server nodes. The simulation showed the packet loss and node failure could be handled, but high rates of these network faults would increase notification delay and the load on the network. |
