2.2.23 E911 Call Syntax

This section describes the E911 call syntax that MUST be used by SIP endpoints to initiate an E911 call. The SIP INVITE is marked by the presence of a Priority header with value "emergency", as specified in [RFC3261] section 20.26, and a geolocation header that identifies the content identifier of the call context that is delivered as an application/pidf+xml MIME part within the body of the request and a Supported header field containing geolocation. The geolocation header is defined in [RFC6442]. The pidf:presence element is specified in Presence Information Data Format (PIDF), as specified in [RFC3863], with a GEOPRIV location object, as specified in [RFC4119], extension for the status value embedded in it. The location-info element embedded in the GEOPRIV element MUST conform to the civic location format specified in [RFC5139]. If the address cannot be trusted to match the location of the endpoint initiating the request, the method element embedded in the GEOPRIV element MUST have the value "Manual". The GEOPRIV status element embedded in the pidf:presence element is followed by an msftE911PidfExtn extension element, as described in section 9.

For an example E911 INVITE, see section 4.14.