IBM® WebSphere® Presence Server Component supports SIP protocol to provide awareness of presence. The application provides a set of SIP servlets and a representational state transfer (REST) interface for handling PUBLISH and SUBSCRIBE requests using either SIP or HTTP.
For SIP Presence Server handles application client requests with a SIP proxy, which passes them to the SIP container. The SIP container analyzes them and sends them to WebSphere Presence Server through SIP servlets. For HTTP requests are handled by an HTTP proxy which passes them to an HTTP container. The HTTP container analyzes them and send them to WebSphere Presence Server through the HTTP servlets.
Presence Server collects, manages, and distributes standard presence information Presence Information Data Format (PIDF). The information contains one or more sets of data. Each data set consists of a status indicator, an optional communication address, and other optional presence information. Users can subscribe to presence information for other users, receive information about other users, or receive notification when that information changes.
Presence Server obtains presence information from the client applications and external presence providers, including external registrars.