A.10 Signalling flows for assignment and transfer of control of a collaborative session

24.3373GPPIP Multimedia (IM) Core Network (CN) subsystem IP Multimedia Subsystem (IMS) inter-UE transferRelease 17Stage 3TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

A.10.1 Introduction

The signalling flows in this subclause demonstrate how a UE-1 can transfer control of the collaborative session to UE-2.

A.10.2 Transfer of control of a collaborative session without media transfer

It is assumed that UE-1 is the controller UE having collaborative session control. A user has a multimedia session on his device UE‑1 with voice (Media A) and video (Media B) media flows. The controller UE, UE-1 initiates the transfer of collaborative session control to UE-2 without transferring media from UE-1.

Figure A.10.2-1: Controller UE transfers collaborative session control without transferring media

NOTE: For clarity, the SIP 100 (Trying) responses are not shown in the signalling flow.

1-2. SIP REFER request (controller UE to intermediate IM CN subsystem entities) – see example in table A.10.2-1

It is assumed that UE-1 and UE-2 have the controller UE functionality. The controller UE wants to transfer control of the collaborative session to UE-2.

UE-1sends a SIP REFER request to the SCC AS containing:

a) the Refer-To header field SIP URI containing:

i) The GRUU of UE 2;

ii) A "body" URI header field containing the <controlTransfer> XML element including the <targetController> element set to the GRUU of UE-2.

b) the Contact header field containing the media feature tag g.3gpp.current-iut-controller set to "passive"

UE-1 does not include the g.3gpp.iut-controller media feature tag in the Contact header field of the SIP REFER request as it is indicating to the SCC-AS that it is transferring control of the collaborative session to UE-2.

Table A.10.2-1: SIP REFER request (UE-1 to SCC AS)

REFER sip:interUEtransfer@example.net SIP/2.0

Via:

To: sip:interUEtransfer@example.net

From: sip:user1_public1@home1.net;tag=13579

Call-ID: cb03a0s09a2sdfglkj490333

CSeq: 93809824 REFER

Max-Forwards: 70

P-Preferred-Identity: "John Doe" <sip:user1_public1@home1.net>

Refer-To: <sip:user2_public2@home2.net;gr=urn:uuid:f81d4fae-7dec-11d0-a762-00a0c91e6bf6?body=<controlTransfer> <targetController=<sip: user2_public2@home2.net;gr=urn:uuid:f81d4fae-7dec-11d0-a762-00a0c91e6bf6>/> </controlTransfer>>

Require: target-dialog

Target-dialog: cb03a0s09a2sdfglkj13579;to-tag=abcdef;from-tag=123456

Referred-By: sip:user1_public1@home1.net

Contact: sip:user1_public1@home1.net;gr=urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91ewxyz;+g.3gpp. current-iut-controller=passive

Accept: message/sipfrag,application/vnd.3gpp.iut+xml

Content-Length: 0

3-4. SIP 200 (OK) response

The SCC AS sends a SIP 200 (OK) response to the controller UE-1 as response to the SIP REFER request.

5-6. SIP NOTIFY request (SCC AS to UE-1 through intermediate IM CN subsystem entities)-

The SCC AS sends a SIP NOTIFY request to UE-1 to notify implicit subscription to the SIP REFER request results.

7-8. SIP 200 (OK) response (UE-1 to SCC AS through intermediate IM CN subsystem entities)

The controller UE, UE-1, acknowledges the SIP NOTIFY request by sending a SIP 200 (OK) response to the SCC AS.

9. SIP re-INVITE request (SCC AS to intermediate IM CN subsystem entities) – see example in table A.10.2-9

The SCC AS sends a SIP re-INVITE request towards the Controllee UE (UE-2). The re-INVITE request contains the XML body from the URI in the Refer-To header field from the SIP REFER request.

Table A.10.2-9: SIP re-INVITE request (SCC AS to IM CN subsystem entities)

INVITE sip:user2_public1@home1.net;gr=urn:uuid:f 81d4fae-7dec-11d0-a765-00a0c91e6bf6 SIP/2.0

Via:

Route:

To: sip:user2_public1@home1.net;abcdef

From: sip:user3_public3@home3.net;tag=123456

Call-ID:

CSeq:

Max-Forwards:

Require:

Referred-By: sip:user1_public1@home1.net

Contact: sip:user3_public3@home3.net;gr=urn:uuid:f81d4fae-17oct-11a1-a678-0054c91eabcd

Allow:

Accept: application/vnd.3gpp.iut+xml

Content-Type: multipart/mixed;boundary="boundary1"

Content-Length: {…}

–boundary1

Content-Type: application/sdp

v=0

o=- 1027933615 1027933615 IN 132.54.76.98

s=-

c=IN IP4 132.54.76.98

t=0 0

m=audio 0 RTP/AVP 97

m=video 3002 RTP/AVP 98 99

b=AS:75

a=rtpmap:98 H263

a=fmtp:98 profile-level-id=0

a=rtpmap:99 MP4V-ES

–boundary1

Content-Type: application/vnd.3gpp.iut+xml;handling=optional

<targetController=<sip:user2_public2@home2.net;gr=urn:uuid:f81d4fae-7dec-11d0-a762-00a0c91e6bf6>/>

</controlTansfer>

–boundary1

10. SIP re-INVITE request (intermediate IM CN subsystem entities to UE-2)

11-12. SIP 200 (OK) response (UE-2 to SCC AS through intermediate IM CN subsystem entities) – see example in table A.10.2-11

UE-2 accepts the transfer of control and indicates this by including a g.3gpp.current-iut-controller media feature tag set to Active in the SIP 200 (OK) response it sends to the SCC AS.

Table A.10.2-11: SIP 200 (OK) response (UE-2 to SCC-AS)

SIP/2.0 200 OK

Via:

To: sip:user1_public2@home1.net;tag=xyzwv

From: sip:interUEtransfer@example.net; tag = 12486

Call-ID:

CSeq:

P-Preferred-Identity:

Contact: sip:user1_public2@home1.net;gr=urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6;+g.3gpp. current-iut-controller=Active

Allow:

Content-Type: application/sdp

Content-Length: (…)

v=0

o=- 1027933615 1027933615 IN IP4 145.23.77.88

s=-

c=145.23.77.88

t=0 0

m=audio 0 RTP/AVP 97

m=video 1302 RTP/AVP 98 99

b=AS:75

a=rtpmap:98 H263

a=fmtp:98 profile-level-id=0

a=rtpmap:99 MP4V-ES

13-14. SIP ACK request (from SCC AS to UE-2)

15-16. SIP NOTIFY request (SCC AS to UE-1) – see example table A.10.2-15

The SCC AS sends a SIP NOTIFY request to the controller UE, UE-1, to inform about the success status of the control transfer. The body of the SIP NOTIFY request contains a sipfrag including the Contact header field containing the g.3gpp.current-iut-controller media feature tag set to Active from the received SIP 200 (OK) response from UE-2

Table A.10.2-15: SIP NOTIFY request (SCC AS to UE-1)

NOTIFY sip:user1_public1@home1.net;gr=urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91ewxyz SIP/2.0

Via:

To: sip:user1_public1@home1.net;tag = 13579

From: sip:interUEtransfer@example.net;tag=2255

Call-ID:

CSeq:

Max-Forwards:

P-Asserted-Identity:

Require:

Contact: sip:sccas1.home1.example.net

Allow:

Event: refer

Subscription-State:terminated; reason=noresource

Content-Type: message/sipfrag ;version=2.0

Content-Length: (…)

SIP/2.0 200 OK

Content-Type=application/sdp

Contact: sip:user1_public2@home1.net;gr=urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6;+g.3gpp. current-iut-controller=Active

v=0

s=-

m=audio 0 RTP/AVP 97

m=video 1302 RTP/AVP 98 99

b=AS:75

a=rtpmap:98 H263

a=fmtp:98 profile-level-id=0

a=rtpmap:99 MP4V-ES

17-18. SIP 200 (OK) response (UE-1 to SCC AS)

The controller UE, UE-1, acknowledges the SIP NOTIFY request by sending a SIP 200 (OK) response to the SCC AS.