8 Numbering, Naming and Addressing

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

8.1 Numbering, Naming and Addressing for SIP message

The following URI formats in SIP messages may be applied at the Ici as standardized in 3GPP TS 24.229 [5]:

– SIP URI defined in IETF RFC 3261 [13];

– tel URI defined in IETF RFC 3966 [14];

– IM URI defined in IETF RFC 3860 [15]; and

– PRES URI defined in IETF RFC 3859 [16].

According to 3GPP TS 24.229 [5], the IBCF acting as an exit or entry point in the IMS network supports these URI formats. These URI formats shall be supported at the roaming II-NNI. The SIP URI format shall be supported at the non-roaming II-NNI. For the loopback traversal scenario both the SIP URI and the tel URI shall be supported. The tel URI, IM URI and PRES URI formats may be supported at the non-roaming II-NNI based on agreement between operators. For the loopback traversal scenario the IM URI and PRES URI may be supported based on agreement between operators. Other URI formats may be supported over the II-NNI depending on the operator agreements.

A global number as defined in IETF RFC 3966 [14] shall be used in a tel URI or in the user portion of a SIP URI with the user=phone parameter when conveyed via a non-roaming II-NNI or for the loopback traversal scenario in the Request-URI and in the P-Asserted-Identity header field, except when agreement exists between the operators to also allow other kinds of numbers.

NOTE 1: In a SIP URI the user portion of the Request-URI represents a telephone number only if the SIP URI includes the user=phone parameter.

NOTE 2: Agreements can exist between operators to allow local number (e.g. national service numbers, business trunking numbers, or private numbers) at a non-roaming II-NNI or for the loopback traversal scenario. A SIP URI with such a number, a user=phone parameter, and a phone-context parameter agreed between the operators can then be used.

NOTE 3: 3GPP TS 24.229 [5] allows to restrict the number within a SIP Request-URI with user=phone parameter at a non-roaming II-NNI or for the loopback traversal scenario to be a global number (i.e. E.164 in international format) via an appropriate Application Server. Suitable configuration by the operator is needed to achieve the desired modification of the format.

NOTE 4: The allowed phone number formats in the P-Asserted-Identity header field of a served user are configured by the operator. According to 3GPP TS 23.003 [35], international E.164 format is used within a P-Asserted-Identity header field.

NOTE 5: The global number format usage within a SIP Request-URI with the user=phone parameter at a non-roaming II-NNI or for the loopback traversal scenario allows the terminating network to find the called subscriber, via HSS interrogation, without any further number translation and thus improves the success of the interconnection between IMS operators.

NOTE 6: According to 3GPP TS 23.003 [35] and 3GPP TS 24.229 [5], public user identity takes the form of either SIP URI or tel URI.

NOTE 7: Agreements can exist between operators to allow the "Unavailable User Identity" as defined in 3GPP TS 23.003 [35] in the P-Asserted-Identity header field at a non-roaming II-NNI or for the loopback traversal scenario.

The optional "oli" and "cpc" tel URI parameters associated with a tel URI or a SIP URI with user=phone are described in 3GPP TS 24.229 [5] clause 7.2A.12 and can be part of the P-Asserted-Identity header field. Depending on operator agreements, those URI parameters may be supported at the non-roaming II-NNI or for the loopback traversal scenario.

The "sos" SIP URI parameter associated with a URI in the Contact header field of a REGISTER request or a 200 (OK) response to REGISTER request is described in 3GPP TS 24.229 [5]. The "sos" SIP URI parameter shall be supported at the roaming II-NNI.

The "sos" SIP URI parameter associated with the Request-URI for all dialogs and standalone SIP requests described in clause 5.2.10.3 of 3GPP TS 24.229 [5] and shall be supported at the roaming II-NNI.

The "rn" and "npdi" number portability parameters for the tel URI and the SIP URI with user=phone as described within IETF RFC 4694 [75] can be part of the Request-URI. Depending on operator agreements these parameters may be exchanged over the non-roaming II-NNI or for the loopback traversal scenario.

NOTE 7: The "rn" and "npdi" parameters can be used to address the entry point of the terminating operator depending on national rules for number portability.

The "isub" tel URI parameter for the tel URI and the SIP URI with user=phone as described within IETF RFC 3966 [14] can be part of the Request-URI, To header field and P-Asserted-Identity header field. Depending on operator agreements, this URI parameter may be exchanged over the II-NNI.

The "premium-rate" tel URI parameter for the tel URI and the SIP URI with user=phone as described within 3GPP TS 24.229 [5] clause 7.2A.17 can be part of the Request-URI. Depending on operator agreements, this URI parameter may be exchanged at the roaming II-NNI.

The public service identity (PSI) that takes a form of a SIP URI without including a port number as described in clause 13.5 of 3GPP TS 23.003 [35] may be exchanged over the II-NNI depending on operator agreements.

8.2 Numbering, Naming and Addressing for SDP

The following URI format in the SDP exchange may be applied at the Ici as standardized in 3GPP TS 24.229 [5]:

– MSRP URI for a session of instant messages defined in IETF RFC 4975 [17].

This URI format shall be supported at the roaming II-NNI and may be supported at the non-roaming II-NNI and for the loopback traversal scenario based on agreement between operators. Other URI formats may be supported over the II-NNI depending on the operator’s agreements.