ITU-T H.248.39 PDF

This Recommendation describes the principles to be used to identify a single session description protocol (SDP) sub-field and how to apply wildcarding to that sub-field. The sub-field may be fully specified, wildcarded (CHOOSE "$" or ALL "*") or not significant "-" (see clause 5.2.2.2). Being able to identify a single sub-field is of use when requesting the MG to choose a parameter, specifying a range or for the purposes of auditing.

This Recommendation contains a package that allows a media gateway controller (MGC) to request multiple SDP parameter values and/or multiple SDP lines to be returned in response to a CHOOSE request. It also allows the linking of multiple CHOOSE wildcards so that they return the same value. A new "maintain value" wildcard, "~", is introduced, which is a short notation syntax (versus the fully specified SDP information) that allows performance optimization as well as the reduction of syntax errors (by avoiding the repetition of redundant information)