## chan_sip

    ${SIPCALLID}         * SIP Call-ID: header verbatim (for logging or CDR matching)
    ${SIPDOMAIN}         * SIP destination domain of an inbound call (if appropriate)
    ${SIPFROMDOMAIN}       Set SIP domain on outbound calls
    ${SIPUSERAGENT}      * SIP user agent (deprecated)
    ${SIPURI}            * SIP uri
    ${SIP_CODEC}           Set the SIP codec for a call
    ${SIP_URI_OPTIONS}   * additional options to add to the URI for an outgoing call
    ${RTPAUDIOQOS}         RTCP QoS report for the audio of this call
    ${RTPVIDEOQOS}         RTCP QoS report for the video of this call