22 Roles for detection of remote leg information

24.2373GPPIP Multimedia (IM) Core Network (CN) subsystem IP Multimedia Subsystem (IMS) service continuityRelease 17Stage 3TS

22.1 Introduction

This clause specifies the procedures for discovery of remote leg information of a dialog anchored in SCC AS.

Procedures are specified for the MSC server enhanced for ICS and SCC AS.

The procedures can be used by MSC server enhanced for ICS only in a dialog where Feature-Cap header field with g.3gpp.remote-leg-info feature-capability indicator was received.

22.2 MSC server enhanced for ICS

22.2.1 Distinction of requests

The MSC server enhanced for ICS needs to distinguish the following SIP requests:

1) SIP INFO request:

A) with Info-Package header field with value g.3gpp.state-and-event; and

B) with application/vnd.3gpp.state-and-event-info+xml MIME body associated with the info package according to IETF RFC 6086 [54] as described in subclause D.2.3, containing a <state-and-event-info> root element, the <state-and-event-info> element containing an <anyExt> element and the <anyExt> element containing a <remoteLegInfoResponse> element with remote leg information.

In the procedures below, such requests are known as "SIP INFO requests carrying the remote leg information".

22.2.2 Discover remote leg information

In order to discover remote leg information of a dialog where Feature-Cap header field with g.3gpp.remote-leg-info feature-capability indicator was received, the MSC server enhanced for ICS shall send a SIP INFO request according to 3GPP TS 24.229 [2] within the dialog. The MSC server enhanced for ICS shall populate the SIP INFO request with:

a) Info-Package header field with value g.3gpp.state-and-event; and

b) application/vnd.3gpp.state-and-event-info+xml MIME body associated with the info package according to IETF RFC 6086 [54] according to subclause D.2.3, containing a <state-and-event-info> root element, the <state-and-event-info> element containing an <anyExt> element, the <anyExt> element containing a <remoteLegInfoRequest> element and the <remoteLegInfoRequest> element indicating the requested remote leg information.

Upon receiving a SIP INFO request carrying the remote leg information in the dialog dialog where Feature-Cap header field with g.3gpp.remote-leg-info feature-capability indicator was received, the MSC server enhanced for ICS shall associate the information received in the SIP INFO request carrying the remote leg information with the dialog of the SIP INFO request carrying the remote leg information.

NOTE: The MSC server enhanced for ICS uses the remote leg information when performing supplementary services on the session transferred by PS to CS access transfer.

The MSC server enhanced for ICS shall ignore any unknown element and any unknown attribute included in the <remoteLegInfoResponse> element of the SIP INFO request carrying the request for the remote leg information.

22.3 SCC AS

22.3.1 Distinction of requests

The SCC AS needs to distinguish the following SIP requests:

1) SIP INFO request:

A) with Info-Package header field with value g.3gpp.state-and-event; and

B) with application/vnd.3gpp.state-and-event-info+xml MIME body associated with the info package according to IETF RFC 6086 [54] as described in subclause D.2.3, containing a <state-and-event-info> root element, the <state-and-event-info> element containing an <anyExt> element and the <anyExt> element containing a <remoteLegInfoRequest> element.

In the procedures below, such requests are known as "SIP INFO requests carrying the request for the remote leg information".

22.3.2 Providing remote leg information

Upon receiving a SIP INFO request carrying the request for the remote leg information in the dialog where SCC AS included the Feature-Cap header field with g.3gpp.remote-leg-info feature-capability indicator, the SCC AS shall send shall send a SIP INFO request according to 3GPP TS 24.229 [2] within the dialog. The SCC AS shall populate the SIP INFO request with:

a) Info-Package header field with value g.3gpp.state-and-event; and

b) application/vnd.3gpp.state-and-event-info+xml MIME body associated with the info package according to IETF RFC 6086 [54] according to subclause D.2.3, containing a <state-and-event-info> root element, the <state-and-event-info> element containing an <anyExt> element and the <anyExt> element containing a <remoteLegInfoResponse> element with remote leg information requested in the SIP INFO request carrying the request for the remote leg information.

The SCC AS shall ignore any unknown element and any unknown attribute included in the <remoteLegInfoRequest> element of the SIP INFO request carrying the request for the remote leg information.

Annex A (informative):
Example signalling flows