24.2813GPPMission Critical Video (MCVideo) signalling controlProtocol specificationRelease 18TS
This clause contains the information required for the IANA registration of info package g.3gpp.mcvideo-info in accordance with IETF RFC 6086 .
I.2.2 g.3gpp.mcvideo-info info package
I.2.2.1 Overall description
The MCVideo client request for MCVideo emergency call origination can also optionally request the origination of an MCVideo emergency alert. Similarly, the MCVideo client request for MCVideo emergency call cancellation can also optionally request the cancellation of an MCVideo emergency alert. A mechanism to inform the MCVideo client that one of the requested actions has been rejected by the controlling MCVideo function is needed to both inform the MCVideo user that one of their requested actions has been rejected and to keep the emergency and imminent peril related state machines maintained by the MCVideo client updated appropriately. Note that a SIP 200 OK has to be sent in the case where the MCVideo emergency call origination request or cancellation request is accepted by the controller to allow the MCVideo user to initiate the MCVideo emergency call and receive updated priority even if the accompanying MCVideo alert request is rejected.
An MCVideo client request for an MCVideo imminent peril call when the targeted MCVideo group is in an in-progress emergency state also needs special handling, as in this case, the call request will be accepted but the MCVideo client needs to be informed that the MCVideo user will be joined to an in-progress MCVideo emergency group call instead of the requested MCVideo imminent peril group call to keep the emergency and imminent peril related state machines maintained by the MCVideo client updated appropriately.
This package is used to transport emergency call, imminent peril and emergency alert indications from the controlling function to the MCVideo client
I.2.2.3 Appropriateness of INFO Package Usage
A number of solutions were discussed for the transportation of the emergency call, imminent peril and emergency alert indications from the controlling function to the MCVideo client. The solutions were:
1) Use of the session related methods (e.g. SIP 200 (OK) response to the SIP INVITE request).
2) Use of the SIP MESSAGE method.
3) Use of the SIP INFO method as described in IETF RFC 6086, by defining a new info package.
The result of the evaluation of the above solutions were:
1) To include such a large amount of data in a SIP 200 (OK) response to an SIP INVITE request could cause problems with the size of the SIP 200 (OK) response resulting in packet fragmentation.
2) The use of the SIP MESSAGE request would result in that the recommended value of size of the information transferred by the SIP MESSAGE request would be exceeded.
3) The use of SIP INFO request was found as the most appropriate solution since the SIP INFO request could be sent in the existing SIP session.
I.2.2.4 Info package name
I.2.2.5 Info package parameters
I.2.2.7 INFO message body parts
The MIME type of the message body carrying participant identities is application/vnd.3gpp.mcvideo-info+xml. The application/vnd.3gpp.mcvideo-info+xml MIME type is defined in 3GPP TS 24.379.
When associated with the g.3gpp.mcvideo-info info package, the Content-Disposition value of the message body carrying mcvideo information is "info-package".
I.2.2.8 Info package usage restrictions
I.2.2.9 Rate of INFO Requests
Single INFO request generated after session set up.
I.2.2.10 Info package security considerations
The security is based on the generic security mechanism provided for the underlying SIP signalling. No additional security mechanism is defined.
I.2.2.11 Implementation details and examples
UAC generation of INFO requests: See 3GPP TS 24.281: "Mission Critical Video (MCVideo) call control; Protocol specification".
UAS processing of INFO requests: See 3GPP TS 24.281: "Mission Critical Video (MCVideo) call control; Protocol specification"
EXAMPLE: A controlling MCVideo function will receive a SIP INVITE request or SIP (re-)INVITE request containing a request for an emergency call (with or without an alert) or an imminent peril call. When an emergency call has been authorised but an optional request for an emergency alert has been determined to be unauthorised, the controller will respond with a SIP 200 (OK) response to indicate acceptance of the call request and return an indication of the rejection of the emergency alert request in a SIP INFO request carrying the application/vnd.3gpp.mcvideo-info+xml MIME body using the g.3gpp.mcvideo-info info package.
Annex J (normative):
MCVideo session control specific concepts for the support of mission critical services over 5GS