scope:

The Session Initiation Protocol (SIP) is a text-based protocol for initiating and managing communication sessions. The protocol is extended by the SIP-events notification framework to provide subscriptions and notifications of SIP events. One example of such event notification mechanism is presence, which is expressed in XML documents called presence documents. SIP can be compressed by using Signaling Compression (SigComp), which is enhanced by using the SIP/ Session Description Protocol (SDP) dictionary to achieve better compression rates. However, the SIP/SDP dictionary is not able to increase the compression factor of (typically lengthy) presence documents. This memo defines the presence-specific static dictionary that SigComp can use in order to compress presence documents to achieve higher efficiency. The dictionary is compression-algorithm independent.