14.1  Introduction

14.2  Home network realm

14.3  Root NAI  Word‑p. 61

The Root NAI shall take the form of a NAI, and shall have the form username@realm as specified in clause 2.1 of IETF RFC 4282.

The username part format of the Root NAI shall comply with RFC 4187 when EAP AKA authentication is used and with RFC 4186, when EAP SIM authentication is used.

When the username part includes the IMSI, the Root NAI shall be built according to the following steps:

1. Generate an identity conforming to NAI format from IMSI as defined in EAP SIM [51] and EAP AKA [50] as appropriate;
2. Convert the leading digits of the IMSI, i.e. MNC and MCC, into a domain name, as described in clause 14.2.

The result will be a root NAI of the form:

"0<IMSI>@wlan.mnc<MNC>.mcc<MCC>.3gppnetwork.org", for EAP AKA authentication and "1<IMSI>@wlan.mnc<MNC>.mcc<MCC>.3gppnetwork.org", for EAP SIM authentication

For example, for EAP AKA authentication: If the IMSI is 234150999999999 (MCC = 234, MNC = 15), the root NAI then takes the form 0234150999999999@wlan.mnc015.mcc234.3gppnetwork.org.

14.4  Decorated NAI

14.4A  Fast Re-authentication NAI  Word‑p. 62

The Fast Re-authentication NAI in both EAP-SIM and EAP-AKA shall take the form of a NAI as specified in clause 2.1 of IETF RFC 4282. If the 3GPP AAA server does not return a complete NAI, the Fast Re-authentication NAI shall consist of the username part of the fast re-authentication identity as returned from the 3GPP AAA server and the same realm as used in the permanent user identity. If the 3GPP AAA server returns a complete NAI as the re-authentication identity, then this NAI shall be used. The username part of the fast re-authentication identity shall be decorated as described in 14.4 if the Selected PLMN is different from the HPLMN.

EXAMPLE 1:

If the fast re-authentication identity returned by the 3GPP AAA Server is 458405627015 and the IMSI is 234150999999999 (MCC = 234, MNC = 15), the Fast Re-authentication NAI for the case when NAI decoration is not used takes the form: 458405627015@wlan.mnc015.mcc234.3gppnetwork.org

EXAMPLE 2:

If the fast re-authentication identity returned by the 3GPP AAA Server is "458405627015@aaa1.wlan.mnc015.mcc234.3gppnetwork.org" and the IMSI is 234150999999999 (MCC = 234, MNC = 15), the Fast Re-authentication NAI for the case when NAI decoration is not used takes the form: 458405627015@aaa1.wlan.mnc015.mcc234.3gppnetwork.org

EXAMPLE 3:

If the fast re-authentication identity returned by the 3GPP AAA Server is 458405627015 and the IMSI is 234150999999999 (MCC = 234, MNC = 15), and the PLMN ID of the Selected PLMN is MCC = 610, MNC = 71, the Fast Re-authentication NAI takes the form: wlan.mnc015.mcc234.3gppnetwork.org !458405627015@wlan.mnc071.mcc610.3gppnetwork.org

14.5  Temporary identities

14.6  Alternative NAI  Word‑p. 63

The Alternative NAI shall take the form of a NAI, i.e. 'any_username@REALM' as specified of RFC 4282. The Alternative NAI shall not be routable from any AAA server.

The Alternative NAI shall contain a username part which is not derived from the IMSI. The username part shall not be a null string.

The REALM part of the NAI shall be "unreachable.3gppnetwork.org".

The result shall be an NAI in the form of:

"<any_non_null_string>@unreachable.3gppnetwork.org"

14.7  W-APN

14.7.1  Format of W-APN Network Identifier

The W-APN Network Identifier follows the format defined for APNs in clause 9.1.1. In addition to what has been defined in clause 9.1.1 the W-APN Network Identifier shall not contain "w-apn." and not end in ".3gppnetwork.org".

A W-APN Network Identifier may be used to access a service associated with a PDG. This may be achieved by defining:

• a W-APN which corresponds to a FQDN of a PDG, and which is locally interpreted by the PDG as a request for a specific service, or
• a W-APN Network Identifier consisting of 3 or more labels and starting with a Reserved Service Label, or a W-APN Network Identifier consisting of a Reserved Service Label alone, which indicates a PDG by the nature of the requested service. Reserved Service Labels and the corresponding services they stand for shall be agreed between operators who have WLAN roaming agreements.

The W-APN Network Identifier for the support of IMS Emergency calls shall take the form of a common, reserved Network Identifier of the form "sos".

As an example, the W-APN for MCC 345 and MNC 12 is coded in the DNS as:

"sos.w-apn.mnc012.mcc345.pub.3gppnetwork.org".

where "sos" is the W-APN Network Identifier and " mnc012.mcc345.pub.3gppnetwork.org " is the W-APN Operator Identifier.

14.7.2  Format of W-APN Operator Identifier  Word‑p. 64

The W-APN Operator Identifier is composed of six labels. The last three labels shall be "pub.3gppnetwork.org". The second and third labels together shall uniquely identify the PLMN. The first label distinguishes the domain name as a W-APN.

For each operator, there is a default W-APN Operator Identifier (i.e. domain name). This default W-APN Operator Identifier is derived from the IMSI as follows:

"w-apn.mnc<MNC>.mcc<MCC>.pub.3gppnetwork.org"

where:

• "mnc" and "mcc" serve as invariable identifiers for the following digits.
• <MNC> and <MCC> are derived from the components of the IMSI defined in clause 2.2.

Alternatively, the default W-APN Operator Identifier is derived using the MNC and MCC of the VPLMN. See TS 24.234 for more information.

The default W-APN Operator Identifier is used in both non-roaming and roaming situations when attempting to translate a W-APN consisting only of a Network Identifier into the IP address of the PDG in the HPLMN.

In order to guarantee inter-PLMN DNS translation, the <MNC> and <MCC> coding used in the "w-apn.mnc<MNC>.mcc<MCC>.pub.3gppnetwork.org" format of the W-APN OI shall be:

• <MNC> = 3 digits
• <MCC> = 3 digits

If there are only 2 significant digits in the MNC, one "0" digit shall be inserted at the left side to fill the 3 digits coding of MNC in the W-APN OI.

As an example, the W-APN OI for MCC 345 and MNC 12 is coded in the DNS as:

"w-apn.mnc012.mcc345.pub.3gppnetwork.org".

14.7.3  Alternative Format of W-APN Operator Identifier

For situations when the PDG serving the W-APN is located in such network that is not part of the GRX (i.e. the Interoperator IP backbone), the default Operator Identifier described in clause 14.7.2 is not available for use. This restriction originates from the ".3gppnetwork.org" domain, which is only available in GRX DNS for actual use. Thus an alternative format of W-APN Operator Identifier is required for this case.

The Alternative W-APN Operator Identifiers shall be constructed as follows:

"w-apn.<valid operator's REALM>"

where:

• <valid operator's REALM> corresponds to REALM names owned by the operator hosting the PDG serving the desired W-APN.

REALM names are required to be unique, and are piggybacked on the administration of the Public Internet DNS namespace. REALM names may also belong to the operator of the VPLMN.

As an example, the W-APN OI for the Operator REALM "notareal.com" is coded in the Public Internet DNS as:

"w-apn.notareal.com".

14.8  Emergency Realm and Emergency NAI for Emergency Cases |R7|  Word‑p. 65

The emergency realm shall be of the form of a home network realm as described in clause 14.2 prefixed with the label "sos." at the beginning of the domain name.

An example of a WLAN emergency NAI realm is:

IMSI in use: 234150999999999;

Where:

• MCC = 234;
• MNC = 15;
• MSIN = 0999999999

Which gives the home network domain name: sos.wlan.mnc015.mcc234.3gppnetwork.org.

The NAI for emergency cases shall be of the form as specified in clauses 14.3 and 14.4, with the addition of the emergency realm as described above for PLMNs where the emergency realm is supported.

When UE is using I-WLAN as the access network for IMS emergency calls and IMSI is not available, the Emergency NAI shall be an NAI compliant with RFC 4282 consisting of username and realm, either constructed with IMEI or MAC address, as specified in TS 33.234. The exact format shall be:

imei<IMEI>@sos.wlan.mnc<visitedMNC>.mcc<visitedMCC>.3gppnetwork.org

or if IMEI is not available,

mac<MAC>@sos.wlan.mnc<visitedMNC>.mcc<visitedMCC>.3gppnetwork.org

The realm part of the above NAI consists of the realm built using the PLMN ID (visitedMCC + visitedMNC) of the PLMN selected as a result of the network selection procedure, as specified in clause 5.2.5.4 of the TS 24.234.

The MNC and MCC shall be with 3 digits coded. If there are only 2 significant digits in the MNC, one "0" digit shall be inserted at the left side to fill the 3 digits coding of MNC in the realm of the NAI.

For example, if the IMEI is 219551288888888, and the selected PLMN is with MCC 345 and MNC 12, the Emergency NAI then takes the form of imei219551288888888@sos.wlan.mnc012.mcc345.3gppnetwork.org.

For example, if the MAC address is 44-45-53-54-00-AB, and the selected PLMN is with MCC 345 and MNC 12, the Emergency NAI then takes the form of mac4445535400AB@sos.wlan.mnc012.mcc345.3gppnetwork.org, where the MAC address is represented in hexadecimal format without separators.