Session Initiation Protocol Service Example - Music on Hold

"Music on hold" is one of the features of telephone systems that is most desired by buyers of business telephone systems. Music on hold means that when one party to a call has the call "on hold", that party’s telephone provides an audio stream (often music) to be heard by the other party. Architectural features of SIP make it difficult to implement music on hold in a way that is fully standardscompliant. The implementation of music on hold described in this document is fully effective, is standards-compliant, and has a number of advantages over the methods previously documented. In particular, it is less likely to produce peculiar user interface effects and more likely to work in systems that perform authentication than the musicon-hold method described in Section 2.3 of RFC 5359.