5 Basic Communication

24.1733GPPIMS Multimedia telephony communication service and supplementary servicesRelease 18Stage 3TS

5.1 IMS communication service identifier

URN used to define the ICSI for the IMS Multimedia Telephony Communication Service: urn:urn-7:3gpp-service.ims.icsi.mmtel. The URN is registered at http://www.3gpp.com/Uniform-Resource-Name-URN-list.html.

Summary of the URN: This URN indicates that the device supports the IMS Multimedia Telephony Communication Service.

The URN is intended primarily for use in the following applications, protocols, services, or negotiation mechanisms:

This URN is most useful in a communications application, for describing the capabilities of a device, such as a phone or PDA.

Examples of typical use: Indicating that a mobile phone can support the IMS Multimedia Telephony Communication Service.

Related standards or documents:

3GPP TS 24.173: "IMS Multimedia Telephony Communication Service and Supplementary Services, stage 3"

5.2 Session control procedures

The IMS multimedia telephony communication service can support different types of media, including media types listed in 3GPP TS 22.173 [2]. The session control procedures for the different media types shall be in accordance with 3GPP TS 24.229 [13] and 3GPP TS 24.247 [14], with the following additions:

a) Multimedia telephony is an IMS communication service and the P-Preferred-Service and P-Asserted-Service headers shall be treated as described in 3GPP TS 24.229 [13]. The coding of the ICSI value in the P-Preferred-Service and P-Asserted-Service headers shall be according to clause 5.1.

b) The multimedia telephony participant shall include the "+g.3gpp. icsi-ref" header field parameter equal to the ICSI value defined in clause 5.1 in the Contact header field in initial requests and responses as described in 3GPP TS 24.229 [13].

c) The multimedia telephony participant shall include an Accept-Contact header field containing the "+g.3gpp.icsi-ref" header field parameter containing the ICSI value defined in clause 5.1 in initial requests. If the multimedia telephony participant supports the IMS data channel usage as specified in 3GPP TS 26.114 [12], then the multimedia telephony participant may include an Accept-Contact header field containing the "sip.app-subtype" media feature tag defined in IETF RFC 5688 [44] with a value of "webrtc-datachannel" in a request for a new dialog or standalone transaction. If the user requests capabilities other than multimedia telephony and IMS data channel, the Accept-Contact header field may contain other feature parameters and feature parameter values, and other Accept-Contact header fields may be added to express user preferences as per IETF RFC 3841 [16].

NOTE 1: How the user indicates other feature parameters and the feature parameter values is outside of the scope of this document.

d) The multimedia telephony application server shall include the "+g.3gpp.icsi-ref" header field parameter equal to the ICSI value defined in clause 5.1 in a Feature-Caps header field in requests sent to the terminating user and in 1xx or 2xx responses to requests from the originating user as described in 3GPP TS 24.229 [13] and IETF RFC 6809 [31].

e) The multimedia telephony participant may use the presence of a "+g.3gpp.icsi-ref" header field parameter equal to the ICSI value defined in clause 5.1 in a Feature-Caps header field in requests and responses as described in IETF RFC 6809 [31] to determine that a multimedia telephony application server is participating in the session and multimedia telephony is the IMS communication service supported for use in the dialog.

NOTE 2: ICSI values with subclass identifiers are considered equal to the value defined in clause 5.1 when determining that the multimedia telephony application server is participating in the session.

f) The multimedia telephony application server may insert a Response-Source header field in accordance with the procedures in clause 5.7.1.0 of 3GPP TS 24.229 [13], where the "role" header field parameter is set to "tas" when initiating a failure response to any received request.

5.3 Interworking

The multimedia telephony participant could receive initial requests that do not contain the ICSI value defined in clause 5.1 in the Accept-Contact header but still invoke the IMS multimedia telephony communication service application.

5.4 Call progress indications

The UE shall support the UE procedures specified in 3GPP TS 24.628 [35].