24.1413GPPPresence service using the IP Multimedia (IM) Core Network (CN) subsystemRelease 17Stage 3TS
The presence service provides the ability for the home network to manage presence information of a user’s device, service or service media even whilst roaming. A user’s presence information may be obtained through input from the user, information supplied by network entities or information supplied by elements external to the home network. Consumers of presence information, watchers, may be internal or external to the home network. The architecture for the 3GPP presence service is specified in 3GPP TS 23.141 .
SIP and XCAP provide means to manipulate the presence status of a user. For details on the differences between those means refer to RFC 3903  and RFC 4827 . For details on the relationship of XCAP server to other roles see subclause 6.2.2.