34 Support for signed attestation for emergency and priority IMS sessions

29.1653GPPInter-IMS Network to Network Interface (NNI)Release 18TS

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

34.1 General

Where a network has requirements on a signed attestation for emergency IMS sessions the "Calling number verification using signature verification and attestation information" and "Priority verification using assertion of priority information" features described in 3GPP TS 24.229 [5] need to be supported.

Where a network has requirements on a signed attestation for priority IMS sessions (e.g., MPS sessions) the "Priority verification using assertion of priority information" feature described in 3GPP TS 24.229 [5] needs to be supported and the "Calling number verification using signature verification and attestation information" feature described in 3GPP TS 24.229 [5] might need to be supported.

Based on inter-operator agreement, the signed attestation for emergency and priority IMS sessions may be supported over the II-NNI as further specified below.

34.2 Calling number verification using signature verification and attestation information

The requirements to support the "Calling number verification using signature verification and attestation information" functionality for emergency and priority IMS sessions over the II-NNI are the same as in clause 29.

34.3 Priority verification using assertion of priority information

"Priority verification using assertion of priority information" functionality, as described in 3GPP TS 24.229 [5], may be supported over the II-NNI.

If the "Priority verification using assertion of priority information" is supported, the related procedures in 3GPP TS 24.229 [5] shall be applied with the requirements in this clause.

An initial INVITE request containing:

– a Resource-Priority header field; and

– optionally, a Priority header field with a "psap-callback" header field value, for emergency call-back cases;

shall be supported at the II-NNI.

An initial INVITE request containing:

– an Identity header field (defined in IETF RFC 8224 [206]); and

– a Priority-Verstat header field (defined in 3GPP TS 24.229 [5] clause 7.2.21)

shall be supported at the non-roaming II-NNI.

A re-INVITE request containing a Resource-Priority header field shall be supported at the II-NNI.

A re-INVITE request containing:

– an Identity header field (defined in IETF RFC 8224 [206]); and

– a Priority-Verstat header field (defined in 3GPP TS 24.229 [5] clause 7.2.21)

shall be supported at the non-roaming II-NNI.

Annex A (informative):
Summary of SIP header fields

A summary of the SIP header fields to be used in case of interconnection by using II-NNI is proposed in table A.1.

The starting point is the sending behaviour described for proxy and UA roles in annex A of 3GPP TS 24.229 [5]:

– In case of misalignment between table A.1 and the behaviour described in 3GPP TS 24.229 [5], the behaviour in 3GPP TS 24.229 [5] has the precedence.

– In case a header field is not described in table A.1 and it is described in 3GPP TS 24.229 [5], the description in 3GPP TS 24.229 [5] is applicable over II-NNI.

– If a header field is not described in 3GPP TS 24.229 [5], the description in table A.1 is applicable over II-NNI.

The definition of the notation codes used in table A.1 is provided in table A.2.

Table A.1: Supported header fields

Item	Header field	Ref.	II-NNI
1	Accept	[5]	m
2	Accept-Contact	[5]	m
3	Accept-Encoding	[5]	m
4	Accept-Language	[5]	m
4a	Accept-Resource-Priority	[5]	o
4b	Additional-Identity	[5], clause 6.1.1.3.1 (table 6.2, item 25) and clause 12.26.2	o in case of a trust relationship between the interconnected networks, else n/a
5	Alert-Info	[5]	o
6	Allow	[5]	m
7	Allow-Events	[5]	m on roaming II-NNI, else o
7a	Attestation-Info	[5], clause 6.1.1.3.1 (table 6.2, item 23) and clause 29	o on non-roaming II-NNI, else n/a
8	Authentication-Info	[5]	m on roaming II-NNI, else n/a
9	Authorization	[5]	m on roaming II-NNI, else n/a
9a	Answer-Mode	[5]	o
10	Call-ID	[5]	m
11	Call-Info	[5]	m
11a	Cellular-Network-Info	clause 6.1.1.3.1 (table 6.2, item 21)	o
12	Contact	[5]	m
13	Content-Disposition	[5]	m
14	Content-Encoding	[5]	m
14a	Content-ID	[5]	o
15	Content-Language	[5]	m
16	Content-Length	[5]	m
17	Content-Type	[5]	m
18	CSeq	[5]	m
19	Date	[5]	m
20	Error-Info	[5]	o
21	Expires	[5]	m
21a	Flow-Timer	[5]	m on roaming II-NNI, else o
21b	Feature-Caps	clause 6.1.1.3.1 (table 6.2, item 13)	o
22	Event	[5]	m
23	From	[5]	m
24	Geolocation	[5]	m
24a	Geolocation-Error	[5]	m
24b	Geolocation-Routing	[5]	m
25	History-Info	clause 6.1.1.3.1 (table 6.2, item 4)	o
25b	Identity	[206], clause 29 and clause 34	o on non-roaming II-NNI, else n/a
25a	Info-Package	[5]	o
26	In-Reply-To	[5]	o
27	Join	[5]	o
27a	Max-Breadth	[5]	m
28	Max-Forwards	[5]	m
29	Min-Expires	[5]	m
30	MIME-Version	[5]	m
31	Min-SE	[5]	m
32	Organization	[5]	m
32a	Origination-Id	[5], clause 6.1.1.3.1 (table 6.2, item 24) and clause 29	o on non-roaming II-NNI, else n/a
33	P-Access-Network-Info	clause 6.1.1.3.1 (table 6.2, item 2)	m in case of a trust relationship between the interconnected networks, else n/a
33a	P-Answer-state	[5]	o
34	P-Asserted-Identity	clause 6.1.1.3.1 (table 6.2, item 1)	m in case of a trust relationship between the interconnected networks, else n/a
35	P-Asserted-Service	clause 6.1.1.3.1 (table 6.2, item 5)	o
35a	P-Associated-URI	[5]	m on roaming II-NNI, else n/a
36	P-Called-Party-ID	[5]	m on roaming II-NNI, else n/a
37	P-Charging-Function-Addresses	clause 6.1.1.3.1 (table 6.2, item 7)	n/a
38	P-Charging-Vector	clause 6.1.1.3.1 (table 6.2, item 6)	m on roaming II-NNI, else o
39	P-Early-Media	clause 6.1.1.3.1 (table 6.2, item 12)	m in case of a trust relationship between the interconnected networks, else n/a
40	P-Media-Authorization	[5]	n/a
41	P-Preferred-Identity	[5]	n/a
42	P-Preferred-Service	[5]	m on roaming II-NNI, else n/a
43	P-Private-Network-Indication	clause 6.1.1.3.1 (table 6.2, item 9)	m on roaming II-NNI, else o
44	P-Profile-Key	clause 6.1.1.3.1 (table 6.2, item 8)	o on roaming II-NNI, else n/a
44a	P-Refused-URI-List	[5]	o on non-roaming II-NNI, else n/a
45	P-Served-User	clause 6.1.1.3.1 (table 6.2, item 10)	m on roaming II-NNI, else n/a
46	P-User-Database	[5]	n/a
47	P-Visited-Network-ID	[5]	m on roaming II-NNI, else n/a
47a	Path	[5]	m on roaming II-NNI, else n/a
47b	Permission-Missing	[5]	o
47c	Policy-Contact	[133] and clause 15.6.2	o
48	Priority	clause 6.1.1.3.1 (table 6.2, item 14)	o
48b	Priority-Share	[5] clause 7.2.16	o on roaming II-NNI, else n/a
48c	Priority-Verstat	[5], clause 6.1.1.3.1 (table 6.2, item 26) and clause 34	o on non-roaming II-NNI, else n/a
48a	Priv-Answer-Mode	[5]	o
49	Privacy	[5]	m
50	Proxy-Authenticate	[5]	m on roaming II-NNI, else n/a
51	Proxy-Authorization	[5]	m on roaming II-NNI, else n/a
52	Proxy-Require	[5]	m
52a	RAck	[5]	m
53	Reason	[5] and clause 6.1.1.3.1 (table 6.2, item 11)	o when in a request. When in a response, m in case of a trust relationship between the interconnected networks, else n/a
54	Record-Route	[5]	m
54a	Recv-Info	[5]	o
55	Referred-By	[5]	m
55a	Refer-Sub	[5]	m in the case the REFER request is supported, else n/a
55b	Refer-To	[5]	m in the case the REFER request is supported, else n/a
56	Reject-Contact	[5]	m
56a	Relayed-Charge	clause 6.1.1.3.1 (table 6.2, item 19)	n/a
57	Replaces	[5]	o
58	Reply-To	[5]	o
59	Request-Disposition	[5]	m
60	Require	[5]	m
61	Resource-Priority	clause 6.1.1.3.1 (table 6.2, item 3)	o
61c	Resource-Share	[5] clause 7.2.13	o on roaming II-NNI, else n/a
61d	Response-Source	[5]	o in case of a trust relationship between the interconnected networks, else n/a
61b	Restoration-Info	clause 6.1.1.3.1 (table 6.2, item 18)	o on roaming II-NNI, else n/a
61a	Retry-After	[5]	o
62	Route	[5]	m
62a	RSeq	[5]	m
63	Security-Client	[5]	n/a
63a	Security-Server	[5]	n/a
64	Security-Verify	[5]	n/a
65	Server	[5]	o
65c	Service-Interact-Info	[5] and clause 6.1.1.3.1 (table 6.2, item 20)	o in case of a trust relationship between the interconnected networks, else n/a
65a	Service-Route	[5]	m on roaming II-NNI, else n/a
65b	Session-ID	[5]	o
66	Session-Expires	[5]	m
66a	SIP-ETag	[5]	m in the case the PUBLISH request is supported, else n/a
66b	SIP-If-Match	[5]	m in the case the PUBLISH request is supported, else n/a
67	Subject	[5]	o
67a	Subscription-State	[5]	m in the case the NOTIFY request is supported, else n/a
67b	Suppress-If-Match	[144] and clause 15.6.4	o
68	Supported	[5]	m
68a	Target-Dialog	[5]	o
69	Timestamp	[5]	m
70	To	[5]	m
71	Trigger-Consent	[5]	m
71a	Unsupported	[5]	m
72	User-Agent	[5]	m
73	User-to-User	[5]	o
74	Via	[5]	m
75	Warning	[5]	o
76	WWW-Authenticate	[5]	m on roaming II-NNI, else n/a

Table A.2: Key to notation codes for SIP header fields

Notation code	Meaning
m	The SIP header field is applicable at II-NNI. Supporting a SIP header field at the II-NNI means that this header field is passed through the IBCF. It does not imply that network elements inside the serving and served networks or user equipment connected to these networks shall support this header field, where 3GPP TS 24.229 [5] is applied. If specified in 3GPP TS 24.229 [5], the IBCF modifies the SIP header field.
o	The applicability of SIP header field at II-NNI depends on bilateral agreement between the operators.
n/a	It is impossible to use the SIP header field at the II-NNI. This header field could be discarded by the IBCF.

Annex B (informative):
Dynamic view of SIP header fields within SIP messages