Section: 8.100 TWAN Identifier
Content: The TWAN Identifier is used for reporting UE location in a Trusted WLAN Access Network (TWAN). See 3GPP TS 23.402[ Architecture enhancements for non-3GPP accesses ]  [45]. TWAN Identifier shall be coded as depicted in Figure 8.100-1. Figure 8.100-1: TWAN Identifier The BSSID and SSID shall be encoded as described in IEEE Std 802.11-2012 [52]. The TWAN identifier shall contain the SSID and, unless otherwise determined by the TWAN operator's policies, it shall contain at least the BSSID, the civic address of the access point to which the UE is attached or the Circuit-ID with the identity of the Relay (e.g. TWAG) which has allocated it (see clause 16.1.7 of 3GPP TS 23.402[ Architecture enhancements for non-3GPP accesses ]  [45]). It may also contain the identifier of the TWAN operator, i.e. either the TWAN PLMN-ID if the TWAN is operated by a mobile operator or the TWAN Operator Name otherwise. The SSID Length in octet '6' indicates the length of the SSID field. The SSID is an Octet String which shall have a maximum length of 32 octets (see IEEE Std 802.11-2012 [52]). The BSSIDI flag in octet 5 indicates whether the BSSID in octets 'k+1' to 'k+6' shall be present. If BSSIDI is set to '1', then the BSSID shall be present. If BSSIDI is set to '0', then the BSSID shall not be present. The BSSID is an Octet String which shall be 6 octets long (see IEEE Std 802.11-2012 [52]). The CIVAI flag in octet 5 indicates whether the Civic Address Length and Civic Address Information in octets 'q' and 'q+1' to 'q+r' shall be present. The Civic Address Length and Information shall be present if and only if the CIVAI flag is set to 1. When present, the Civic Address Information shall contain the civic address of the Access Point to which the UE is attached and it shall be encoded as defined in clause 3.1 of IETF RFC 4776 [59] excluding the first 3 octets. The PLMNI flag in octet 5 indicates whether the TWAN PLMN-ID in octets 's' to 's+2' shall be present. The TWAN PLMN-ID shall be present if and only if the PLMNI flag is set to 1. The TWAN PLMN-ID shall be encoded as octets 5 to 7 of the Serving Network IE in clause 8.18. When present, the TWAN PLMN-ID shall indicate the PLMN-ID of the TWAN operator. NOTE: the PLMN ID contained in the TWAN PLMN-ID can differ from the PLMN ID in the Serving Network IE. The OPNAI flag in octet 5 indicates whether the TWAN Operator Name Length and TWAN Operator Name in octets 't' and 't+1' to 't+u' shall be present. The TWAN Operator Name Length and TWAN Operator Name shall be present if and only if the OPNAI flag is set to 1. The TWAN Operator Name shall be encoded as specified in clause 19. 8 of 3GPP TS 23.003[ Numbering, addressing and identification ]  [2]. When present, the TWAN Operator Name shall indicate the identifier of the TWAN operator. The LAII flag in octet 5 indicates whether the Logical Access ID information is present in the TWAN Identifier IE. The Logical Access ID is encoded by the Relay Identity information in octets 'v' to 'v+w' and the Circuit-ID information in octets 'x' to 'x+y'. The Relay Identity information and the Circuit-ID information shall be present if the LAII flag is set to '1'. The Relay indicates a DHCP relay agent as defined in IETF RFC 3046 [60]. The Relay Identity Type indicates the type of the Relay Identity as described in Table 8.100-1. The Relay Identity Length indicates the length of the Relay Identity. In case the Relay Identity Type indicates an IP address, the length indicates if it is IPv4 or IPv6 address of the Relay. The length is 4 octets for IPv4 and 16 octets for IPv6. If the Relay Identity type is set to 1 (i.e. an FQDN), it is encoded as described in clause 3.1 of IETF RFC 1035 [31] but excluding the trailing zero byte. The Circuit-ID length indicates the length of the Circuit-ID. The Circuit-ID is as defined in IETF RFC 3046 [60], it is encoded as an Octetstring and provided by the Relay. Table 8.100-1: Relay Identity Type