A.5.5 Signalling flows for termination to an ICS UE with CS media using Gm reference point when using an MSC Server enhanced for ICS and UE assisted T-ADS

24.2923GPPIP Multimedia (IM) Core Network (CN) subsystem Centralized Services (ICS)Release 17Stage 3TS

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

Figure A.5.5-1 shows the termination of a call to an ICS UE using CS bearers controlled through the IM CN subsystem. In this example the MSC Server is enhanced for ICS and is capable of translating NAS signalling received from the ICS UE to SIP and vice versa. In this example, the UE supports UE assisted terminating access domain selection.

Figure A.5.5-1: ICS UE termination with CS media using Gm reference point when using an MSC Server enhanced for ICS – UE assisted T-ADS

The details of the signalling flows are as follows:

1-5: These steps are identical to steps 1-5 described in subclause A.5.3.

The SDP shows that local preconditions on the originating side are met.

6. Terminating Access Domain Selection

The SCC AS performs initial T-ADS selecting IMS for the service control signalling when UE-B is registered in the IMS.

7. SIP INVITE request (SCC AS to intermediate IM CN subsystem entities) – see example in Table A.5.5-7.

The SCC AS, acting as a routing B2BUA, generates a SIP INVITE request based upon the received SIP INVITE request and sends it to the intermediate subsystem entities.

Table A.5.5-7: SIP INVITE request (SCC AS to intermediate IM CN subsystem entities)

INVITE sip:user2_public1@home1.net SIP/2.0

Via: SIP/2.0/UDP sccas.home1.net;branch=z9hG4bKnas34r5

Max-Forwards: 65

Route: <sip:cb03a0s09a2sdfglkj490333@scscf1.home1.net;lr>;orig-dialog-id="O:73935718_92645110-712786jd246395302d-zKE"

Record-Route:<sccas.home1.net;lr>

P-Access-Network-Info:

P-Asserted-Identity:

P-Charging-Function-Addresses: ccf=[5555::b99:c88:d77:e66]; ccf=[5555::a55:b44:c33:d22]; ecf=[5555::1ff:2ee:3dd:4ee]; ecf=[5555::6aa:7bb:8cc:9dd]

P-Charging-Vector:

P-Asserted-Service:

Accept-Contact: *;+g.3gpp.icsi-ref="urn%3Aurn-7%3gpp-service.ims.icsi.mmtel"

Accept-Contact: *;+g.3gpp.ics="principal";explicit;require

Privacy:

From: <sip:user2_public1@home2.net>;tag=171828

To:

Call-ID:

Cseq:

Supported:

Accept:

Contact:

Allow:

Content-Type:

Content-Length:

v=0

o=2987933615 2987933615 IN IP6 5555::eee:ccc:aaa:bbb

s=-

c=IN IP6 5555::eee:fff:aaa:bbb

t=0 0

a=creq:med-v0

m=audio 49170 RTP/AVP 97 3 98

a= rtpmap:97 AMR/8000/1

a=fmtp:97 mode-set=0,2,5,7; maxframes=2

a=rtpmap:98 telephone-event/8000

a=fmtp:98 0-15

a=ccap:2 PSTN E164 +12125556666

a=tcap:2 PSTN

a=omcap:4 –

a=acap:1 setup:actpass

a=acap:2 connection:new

a=pcfg:1

a=pcfg:2 t=2 m=4 c=2 a=1,2

a=curr:qos local none

a=curr:qos remote none

a=des:qos mandatory local sendrecv

a=des:qos optional remote sendrecv

8. SIP 100 (Trying) response (intermediate IM CN subsystem entities to SCC AS)

The intermediate IM CN subsystem entities respond to the SCC AS with a SIP 100 (Trying) response. There is no ICS specific content in this response.

9. SIP INVITE request (intermediate IM CN subsystem entities to ICS UE B)

The SIP INVITE request is routed towards the called party ICS UE B since further iFC evaluation is not necessary.

10. SIP 100 (Trying) response (ICS UE B to intermediate IM CN subsystem entities)

The ICS UE B responds to the intermediate IM CN subsystem entities with a SIP 100 (Trying) response. There is no ICS specific content in this response.

11. Terminating Access Domain Selection

The ICS UE performs T-ADS. In this example the UE chooses a CS bearer for media

12 SIP 183 (Session Progress) response (ICS UE to intermediate IM CN subsystem entities) – see example in table A.5.5-12

The ICS UE generates a SIP 183 (Session Progress) response based upon the received SIP INVITE request and indicates in the SDP that the CS media bearer is used.

Table A.5.5-12: SIP 183 (Session Progress) response (IMS UE to intermediate IM CN subsystem entities)

SIP/2.0 183 Session Progress

Via: SIP/2.0/UDP pcscf1.home1.net;branch=z9hG4bK240f34.1,

SIP/2.0/UDP scscf1.home1.net;branch=z9hG4bK332b23.1,

SIP/2.0/UDP sccas .home1.net;branch=z9hG4bKnas34r5,

Record-Route: <sip:pcscf1.home1.net;lr;<sip:scscf1.home1.net;lr>;<sip:sccas .home1.net;lr>

P-Access-Network-Info: 3GPP-UTRAN-FDD; utran-cell-id-3gpp=234151D0FCE11

P-Charging-Vector: icid-value="AyretyU0dm+6O2IrT5tAFrbHLso=023551024"

Privacy: none

From: <sip:user2_public1@home2.net>;tag=171828

To: <tel:+1-212-555-2222>;tag=171820

Call-ID:

CSeq:

Require: 100rel

Contact: <sip:user1_public1@home1.net;gr=urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>;+g.3gpp.icsi-ref="urn%3Aurn-7%3gpp-service.ims.icsi.mmtel";+g.3gpp.ics="principal"

Allow: INVITE, ACK, CANCEL, BYE, PRACK, UPDATE, REFER, MESSAGE

Content-Type: application/sdp

Content-Length: (…)

v=0

o=2987933615 2987933615 IN IP6 5555::aaa:bbb:ccc:ddd

t=0 0

m=audio 9 PSTN –

c=PSTN – –

a=acfg:2 t=2 m=4 c=2 a=1,2

a=setup:active

a=connection:new

a=cs-correlation:callerid:+12125552222

a=curr:qos local none

a=curr:qos remote none

a=des:qos mandatory local sendrecv

a=des:qos mandatory remote sendrecv

14. SETUP message (ICS UE B to MSC Server enhanced for ICS)

The ICS UE B inititates bearer setup in the CS domain by sending a SETUP message to the MSC Server enhanced for ICS.

Specifically for this signalling flow, the SETUP message includes:

– Called Party Number information element = = [(Numbering plan identifier = ISDN/telephony numbering plan), (type of number = international number ), (Number digits = 1212556666)]. The Called Party Number information element is set to the SCC AS PSI DN.

– Bearer Capability information element = [(information transfer capability = speech), (speech versions = FR AMR, GSM EFR, GSM FR)]

– Supported Codec List information element = {[(SysID 1 = UMTS), (Codec Bitmap for SysID 1 = UMTS AMR 2)], [(SysID 2 = GSM), (Codec Bitmap for SysID 2 = FR AMR, GSM EFR, GSM FR)]}

The MSC Server enhanced for ICS knows the calling party number corresponding to the ICS UE B.

15. CALL PROCEEDING message (MSC Server enhanced for ICS to ICS UE B)

Upon receipt of the SETUP message from the ICS UE B, the MSC Server enhanced for ICS responds with a CALL PROCEEDING message. There is no ICS specific content in this message.

16. SIP PRACK request (SCC AS to IM CN subsystem entities)

SCC AS acknowledges the receipt of SIP 183 (Session Progress) response.

16. SIP PRACK request and SIP 200 (OK) response

The SCC AS sends a SIP PRACK request towards the ICS UE via the intermediate IM CN subsystem entities as a result of receiving the reliably sent SIP 183 (Session Progress) response containing the SDP answer.

Upon receipt of the SIP PRACK request, the ICS UE responds with a SIP 200 (OK) response towards the SCC AS via the intermediate IM CN subsystem entities.

The is no ICS specific content in these SIP messages.

17. SIP INVITE request (MSC Server enhanced for ICS to intermediate IM CN subsystem entities) – see example in A.5.5-17.

The MSC Server enhanced for ICS maps the received SETUP message to a SIP INVITE request which is routed towards the intermediate IM CN subsystem entities. The INVITE request is addressed to the SCC AS PSI DN in the Request-URI.

Table A.5.5-17: SIP INVITE request (MSC Server enhanced for ICS to intermediate IM CN subsystem entities)

INVITE tel:+1-212-555-6666 SIP/2.0

Via: SIP/2.0/UDP msc2.home1.net;branch=z9hG4bKnashds7

Max-Forwards: 70

Route: <sip:icscf2.home1.net:lr>

P-Asserted-Identity: <tel: +1-212-555-2222>

P-Charging-Vector: icid-value="AyretyU0dm+6O2IrT5tAFrbHLso=023551024"; orig-ioi=home2.net

P-Access-Network-Info:

Privacy: none

Accept-Contact: *;+g.3gpp.icsi-ref="urn%3Aurn-7%3gpp-service.ims.icsi.mmtel"

From: <sip:user2_public1@home1.net>;tag=276859

To: <tel:+1-212-555-6666>

Call-ID: f81d4fae-7dec-11d0-a765-00a0c91e6bf6

Cseq: 127 INVITE

Supported: 100rel, precondition, gruu, 199

Contact: <sip:user2_public1@home1.net;gr=urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>;+g.3gpp.icsi-ref="urn%3Aurn-7%3gpp-service.ims.icsi.mmtel";+g.3gpp.ics="server"

Allow: INVITE, ACK, CANCEL, BYE, PRACK, UPDATE, REFER

Content-Type: application/sdp

Content-Length: (…)

v=0

o=- 2987933615 2987933615 IN IP6 5555::aaa:bbb:ccc:fff

c=IN IP6 5555::aaa:bbb:ccc:fff

t=0 0

m=audio 3456 RTP/AVP 97 96

b=AS:25.4

a=curr:qos local sendrecv

a=curr:qos remote none

a=des:qos mandatory local sendrecv

a=des:qos none remote sendrecv

a=rtpmap:97 AMR

a=fmtp:97 mode-set=0,2,5,7; mode-change-period=2

a=rtpmap:96 telephone-event

a=maxptime:20

Request-URI: SCC AS PSI DN as received in the SETUP message.

P-Asserted-Identity: The MSC Server enhanced for ICS inserts the tel-URI containing the subscriber number, as received from the ICS UE B.

Accept-Contact: The MSC Server enhanced for ICS includes the mmtel feature tag in the INVITE request .

Contact: The MSC Server enhanced for ICS includes the GRUU received at registration, the media feature tag g.3gpp.icsi-ref set to "urn%3Aurn-7%3gpp-service.ims.icsi.mmtel" and the media feature tag g.3gpp.ics set to "server".

SDP: The SDP contains preconfigured set of codecs supported by the MGW.

18. SIP 100 (Trying) response (intermediate IM CN subsystem entities to MSC Server enhanced for ICS)

The intermediate IM CN subsystem entities respond to the MSC Server enhanced for ICS with a SIP 100 (Trying) response. There is no ICS specific content in this response.

19. SIP INVITE request (intermediate IM CN subsystem entities to SCC AS) – see example in Table A.5.5-19

The SIP INVITE request is sent to the SCC AS.

Table A.5.5-19: SIP INVITE request (intermediate IM CN subsystem entities to SCC AS)

INVITE tel:+1-212-555-6666 SIP/2.0

Via: SIP/2.0/UDP scscf2.home2.net;branch=z9hG4bK332b33.1,SIP/2.0/UDP icscf1.home1.net;branch=z9hG4bK871y12.1, SIP/2.0/UDP msc2.home1.net;branch=z9hG4bKnashds7

Max-Forwards: 68

Route: <sip:sccas.home1.net:lr>, <sip:scscf1.home1.net;lr>;orig-dialog-id="yuflsae80r3rb3fh31ondyr829cnyr381cn932YDWref0w0-wwtg374"

Record-Route: <sip:scscf1.home1.net;lr>

P-Asserted-Identity:

P-Charging-Vector:

P-Access-Network-Info:

Privacy:

From:

To:

Call-ID:

Accept-Contact:

Cseq:

Supported:

Contact:

Allow:

Content-Type:

Content-Length: (…)

o=-

20. SIP 100 (Trying) response (SCC AS to intermediate IM CN subsystem entities)

The SCC AS responds to the intermediate IM CN subsystem entities with a SIP 100 (Trying) response. There is no ICS specific content in this response.

21. SIP 200 (OK) response (SCC AS to intermediate IM CN subsystem entities) – see example in table A.5.5-21.

The SCC AS responds to the SIP INVITE request with a SIP 200 (OK) response that includes an SDP answer. The SDP shows local preconditions as received in the SIP INVITE request in step 4.

Table A.5.5-21: SIP 200 (OK) response (SCC AS to intermediate IM CN subsystem entities)

SIP/2.0 200 OK

Via: SIP/2.0/UDP scscf1.home1.net;branch=z9hG4bK332b33.1,SIP/2.0/UDP icscf1.home1.net;branch=z9hG4bK871y12.1, SIP/2.0/UDP msc2.home1.net;branch=z9hG4bKnashds7

Record-Route: <sip:sccas.home1.net;lr>,<sip:scscf1.home1.net;lr>

P-Access-Network-Info:

Privacy: none

From: <tel: +1-212-555-2222>;tag=276859

To: <tel:+1-212-555-6666>;tag=347529

Call-ID: f81d4fae-7dec-11d0-a765-00a0c91e6bf6

CSeq:

Require: 100rel, precondition

Contact:<sip:user1_public1@home2.net;gr=urn:uuid:2ad8950e-48a5-4a74-8d99-ad76cc7fc74>;+g.3gpp.icsi-ref="urn%3Aurn-7%3gpp-service.ims.icsi.mmtel">

Allow: INVITE, ACK, CANCEL, BYE, PRACK, UPDATE, REFER, MESSAGE

Content-Type: application/sdp

Content-Length: (…)

v=0

o=- 2987933623 2987933623 IN IP6 5555::aaa:bbb:ccc:ddd

s=-

c=IN IP6 5555::aaa:bbb:ccc:ddd

t=0 0

m=audio 3456 RTP/AVP 97 96

b=AS:25.4

a=curr:qos local sendrcv

a=curr:qos remote sendrcv

a=des:qos mandatory local sendrecv

a=des:qos mandatory remote sendrecv

a=rtpmap:97 AMR

a=fmtp:97 mode-set=0,2,5,7; mode-change-period=2

a=maxptime:20

22. SIP 200 (OK) response (intermediate IM CN subsystem to MSC Server enhanced for ICS)

The intermediate IM CN subsystem entities route the SIP 200 (OK) response to the MSC Server enhanced for ICS.

23. CONNECT message (MSC Server enhanced for ICS to ICS UE B)

The enhance MSC Server maps the received SIP 200 (OK) response to a CONNECT message. There is no ICS specific content in this message.

24. CONNECT ACKNOWLEDGEMENT message (ICS UE B to MSC Server enhanced for ICS)

The ICS UE A sends a CONNECT ACKNOWLEDGMENT message upon receiving the CONNECT message. There is no ICS specific content in this message.

25-26. SIP ACK request (MSC Server enhanced for ICS to SCC AS via intermediate IM CN subsystem entities)

The MSC Server enhanced for ICS interworks the received CONNECT ACKNOWLEDGEMENT message to a SIP ACK request which is routed to the SCC AS via the intermediate IM CN subsystem entities. There is no ICS specific content in this response.

27-28. SIP 180 (Ringing) response (ICS UE B to SCC AS via intermediate IM CN subsystem entities)

The ICS UE B responds to the received SIP INVITE request with a SIP 180 (Ringing) response. The response contains no SDP body and contains no ICS specific content. The SIP 180 (Ringing) response is routed to the SCC AS.

29-30. SIP 180 (Ringing) response (SCC AS to originating IM CN subsystem via intermediate IM CN subsystem entities)

The SCC AS routes the received SIP 180 (Ringing) response towards the originating network and the calling party.

31. SIP 200 (OK) response (ICS UE B to intermediate IM CN subsystem entities) – see example in Table A.5.5-27

The ICS UE B responds to the received initial SIP INVITE request with a SIP 200 (OK) response. This SIP 200 (OK) does not include an SDP body.

32. SIP 200 (OK) response (intermediate IM CN subsystem entities to SCC AS)

The SIP 200 (OK) response from the ICS UE is routed towards the SCC AS.

33-34. SIP 200 (OK) response (SCC AS to originating IM CN subsystem via intermediate IM CN subsystem entities)

The SIP 200 (OK) response is routed towards the originator of the session in the originating IM CN subsystem. This SIP 200 (OK) response includes an SDP answer the correponds to the SDP received from the MSC server enhanced for ICS and indicates that local preconditions are met.

Table A.5.5-33: SIP 200 (OK) response (SCC AS to intermediate IM CN subsystem entities)

SIP/2.0 200 OK

Via: SIP/2.0/UDP scscf1.home1.net;branch=z9hG4bK332b33.1,SIP/2.0/UDP icscf1.home1.net;branch=z9hG4bK871y12.1, SIP/2.0/UDP scscf1.home2.net;branch=z9hG4bK332b23.1, SIP/2.0/UDP pcscf1.visited2.net;branch=z9hG4bK431h23.1, SIP/2.0/UDP [5555::aaa:bbb:ccc:ddd]:1357;comp=sigcomp;branch=z9hG4bKnashds7

Record-Route: <sip:pcscf1.visited1.net;lr>, <sip:scscf1.home1.net;lr>, <sccas.home1net;lr>

P-Access-Network-Info: 3GPP-UTRAN-FDD; utran-cell-id-3gpp=234151D0FCE11

Privacy: none

From: <tel: +1-212-555-1111>;tag=171828

To: <tel:+1-212-555-2222>;tag=684213

Call-ID: cb03a0s09a2sdfglkj490333

CSeq:

Require: 100rel, precondition

Contact:<sip:user2_public1@home1.net;gr=urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>;+g.3gpp.icsi-ref="urn%3Aurn-7%3gpp-service.ims.icsi.mmtel"

Allow: INVITE, ACK, CANCEL, BYE, PRACK, UPDATE, REFER, MESSAGE

Content-Type: application/sdp

Content-Length: (…)

v=0

o=- 2987933623 2987933623 IN IP6 5555::aaa:bbb:ccc:eee

s=-

c=IN IP6 5555::aaa:bbb:ccc:eee

t=0 0

m=audio 3456 RTP/AVP 97 96

a=curr:qos local sendrcv

a=curr:qos remote sendrcv

a=des:qos mandatory local sendrecv

a=des:qos mandatory remote sendrecv

a=rtpmap:97 AMR

a=fmtp:97 mode-set=0,2,5,7; mode-change-period=2

a=maxptime:20

35-36. SIP ACK request (originating IM CN subsystem to SCC AS via intermediate IM CN subsystem entities and SCC AS)

The originating IM CN subsystem sends a SIP ACK request to the SCC AS via the intermediate IM CN subsystem entities. There is no ICS specific content in this response.

37-38. SIP ACK request (SCC AS to ICS UE B via intermediate IM CN subsystem entities and SCC AS)

The SCC AS sends a SIP ACK request to the ICS UE B via the intermediate IM CN subsystem entities. There is no ICS specific content in this response.