E.3 INFO package for transfer of access transfer events
24.2373GPPIP Multimedia (IM) Core Network (CN) subsystem IP Multimedia Subsystem (IMS) service continuityRelease 17Stage 3TS
E.3.1 Scope
This annex contains the information required for the IANA registration of info package g.3gpp.access-transfer-events in accordance with IETF RFC 6086 [54].
E.3.2 g.3gpp.access-transfer-events info package
E.3.2.1 Overall description
This info packages enables SIP entities to inform each other about events occuring during access transfer of session between access networks. E.g. during CS to PS single radio voice call continuity access transfer the MSC server needs to inform ATCF about the session transfer notification request, ATCF needs to inform MSC server about the session transfer notification response and MSC server needs to inform ATCF about the session transfer preparation.
E.3.2.2 Applicability
The info package mechanism has been selected since the transported information cannot be sent in media plane as entities receiving the information are not mandated to always anchor the media and since usage of subscription in order to transport the information has not been seen as feasible as the information can be exchanged bidirectionally.
E.3.2.3 Info package name
g.3gpp.access-transfer-events
E.3.2.4 Info package parameters
"et" when included in the Recv-Info header field and when Accept header field is not present in the SIP message, the "et" parameter value is a comma delimited list of the values of the "event-type" attribute of the <event> element of the <events> root element which the sender of the Recv-Info header field is able to receive. The <events> root element is defined in XML schema of the MIME type application/vnd.3gpp.access-transfer-events+xml. This parameter applies for the Recv-Info header field and does not apply for the Info-Package header field.
E.3.2.5 SIP option tags
None defined
E.3.2.6 INFO message body parts
The MIME type of the message body carrying events information is application/vnd.3gpp.access-transfer-events+xml. The application/vnd.3gpp.access-transfer-events+xml MIME type is defined in 3GPP TS 24.237.
When associated with the g.3gpp.access-transfer-events info package, the Content-Disposition value of the message body carrying participant identities is "info-package".
E.3.2.7 Info package usage restrictions
None defined.
E.3.2.8 Rate of INFO requests
The rate of the INFO requests depends on the supported event types.
E.3.2.9 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.
E.3.2.10 Implementation details and examples
UAC generation of INFO requests: See 3GPP TS 24.237: "IP Multimedia Subsystem (IMS) Service Continuity; Stage 3"
UAS processing of INFO requests: See 3GPP TS 24.237: "IP Multimedia Subsystem (IMS) Service Continuity; Stage 3"
Examples: See 3GPP TS 24.237: "IP Multimedia Subsystem (IMS) Service Continuity; Stage 3"
Annex F (informative):
Access transfer scenarios