Now that the basic SIP specification has been completed, The MMUSIC working group aims to create a set of building blocks that build, incrementally, on this specification, making it useful for more specialized applications or satisfying additional domain-specific requirements. In my view, the ideal case is that these can be decomposed, where each building block is useful for more than one application or solves more than one problem. So far, we've identified these areas:
Beyond these specific extensions, guidelines for mapping other signaling protocols, such as Q.931, ISUP and H.323, into SIP need to be developed. These guidelines would not add any components to SIP and the extensions, but rather provide information to implementors on how to combine the various elements to achieve the desired functionality.