A.3 USSI AS sending USSD request, no further information required

24.3903GPPRelease 17Stage 3TSUnstructured Supplementary Service Data (USSD) using IP Multimedia (IM) Core Network (CN) subsystem IMS

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

In the example flow at the figure A.3-1, the USSI AS sends a USSD request. The UE does not require further information, the USSD operation is successful and the UE hosting the USSD application indicates sends a USSD response towards USSI AS.

Figure A.3-1: USSI AS sends USSD request

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

1. USSI AS sends INVITE request containing the USSD request — see example in table A.3-1

As a result of some associated procedure between the user and the network, a need is seen to request confirmation using USSD.

USSI AS sends the INVITE request.

By including the Recv-Info header field, the USSI AS indicates its support for the g.3gpp.ussd info package.

Table A.3-1: INVITE request (USSI AS to S-CSCF)

INVITE sip:user1_public1@home1.net SIP/2.0

Via: SIP/2.0/UDP [5555::aaa:bbb:ccc:ddd]:1357;branch=z9hG4bKnashds7

Max-Forwards: 70

Route: <sip:pcscf1.visited1.net:7531;lr>, <sip:scscf1.home1.net;lr>

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

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

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

Privacy: none

From: <sip:ussias_public1@home1.net>;tag=171828

To: <sip:user1_public1@home1.net>

Call-ID: cb03a0s09a2sdfglkj490333

Cseq: 127 INVITE

Supported: precondition, 100rel

Contact: <ussias_public1@home1.net;

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

Accept: application/sdp; application/3gpp-ims+xml; application/vnd.3gpp.ussd+xml

Recv-Info: g.3gpp.ussd

Content-Type: multipart/mixed; boundary=outer

Content-Length: (…)

–outer

Content-Type: application/sdp

v=0

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

s=-

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

t=0 0

m=audio 0 RTP/AVP 97 96

a=rtpmap:97 AMR

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

a=rtpmap:96 telephone-event

–outer

Content-Type: application/vnd.3gpp.ussd+xml

<?xml version="1.0" encoding="UTF-8"?>

<ussd-data>

<ussd-string>Please verify you want require this service. If yes please enter PIN</ussd-string>

<UnstructuredSS-Request/>

</anyExt>

</ussd-data>

–outer—

Application/vnd.3gpp.ussd+xml MIME body: USSD message. The content of the <ussd-string> element included in the INVITE message must be equal to the dialstring inserted in the Request-URI.

2. INVITE request (S-CSCF to P-CSCF)

The S-CSCF forwards the INVITE request based on the Request-URI field.

3. INVITE request (P-CSCF to UE-1)

The P-CSCF forwards the INVITE request containing the USSD message to the UE.

4. 200 (OK) response (UE-1 to P-CSCF)

The UE sends a 200 (OK) response confirming the receipt of the INVITE request and to establish the dialog. The SIP 200 (OK) response will contain a Recv-Info header field set to g.3gpp.ussd.

5. 200 (OK) response (P-CSCF to S-CSCF)

The P-CSCF forwards the 200 (OK) response along the Via header field.

6. 200 (OK) response (S-CSCF to USSI AS)

The S-CSCF forwards the 200 (OK) response along the Via header field to the USSI AS.

7. ACK request (USSI AS to S-CSCF)

The USSI AS responds to the 200 (OK) response with an ACK request sent to the S-CSCF.

8. ACK request (S-CSCF to P-CSCF)

The S-CSCF forwards the ACK request to the P-CSCF.

9. ACK request (P-CSCF to UE-1)

The P-CSCF forwards the ACK request to the UE.

10. USSD operation

The UE performs the requested USSD operation. Details of USSD processing and associated MMI are outside the scope of this specification.

In this example the USSD operation is successful and a response indicating success will be sent to the USSI AS.

11. INFO request (UE1 to P-CSCF) — see example in table A.3-2

Table A.1-2: INFO request (UE-1 to P-CSCF)

INFO sip:ussias_public1@home1.net SIP/2.0

Via SIP/2.0/UDP sip:user_1.home1.net;branch=z9hG4bK332b23.1

Max-Forwards: 70

Route: <sip:pcscf1.home1.net;lr>, <sip:scscf1.visited1.net:7531;lr>

From: <user_1@home1.net;tag=314159

To: <ussias_public1@home1.net;tag=171828

Call-ID: cb03a0s09a2sdfglkj490334

Cseq: 129 INFO

Content-Type: application/vnd.3gpp.ussd+xml

Content-Length:

<?xml version="1.0" encoding="UTF-8"?>

<ussd-data>

<ussd-string>

Yes

</ussd-string>

</ussd-data>

Application/vnd.3gpp.ussd+xml MIME body: USSD message.

12. INFO request (P-CSCF to S-CSCF)

The P-CSCF forwards the INFO request to the S-CSCF.

13. INFO request (S-CSCF to USSI AS)

The S-CSCF forwards the INFO request to the USSI AS. The USSI AS recognizes the application/vnd.3gpp.ussd+xml.

14. 200 (OK) response (USSI AS to S-CSCF)

The USSI AS sends a 200 (OK) response confirming the INFO request.

15. 200 (OK) response (S-CSCF to P-CSCF)

The S-CSCF forwards the 200 (OK) response to the P-CSCF.

16. 200 (OK) response (P-CSCF to UE-1)

The P-CSCF forwards the 200 (OK) response to the UE.

17. BYE request (USSI AS to S-CSCF)

The USSI AS considers the transaction complete and sends a BYE request.

18. BYE request (S-CSCF to P-CSCF)

The S-CSCF forwards the BYE request to the P-CSCF.

19. BYE request (P-CSCF to UE)

The P-CSCF forwards the BYE request to the UE.

20. 200 (OK) response (UE to P-CSCF)

The UE responds to the BYE request with a 200 (OK) response.

21. 200 (OK) response (P-CSCF to S-CSCF)

The P-CSCF forwards to the 200 (OK) response to the S-CSCF.

22. 200 (OK) response (S-CSCF to USSI AS)

The S-CSCF forwards the 200 (OK) response to the USSI AS.