Section: 8.66 Fully Qualified Domain Name (FQDN)
Content: Fully Qualified Domain Name (FQDN) is coded as depicted in Figure 8.66-1. Figure 8.66-1: Fully Qualified Domain Name (FQDN) The FQDN field encoding shall be identical to the encoding of a FQDN within a DNS message of clause 3.1 of IETF RFC 1035 [31] but excluding the trailing zero byte. NOTE 1: The FQDN field in the IE is not encoded as a dotted string as commonly used in DNS master zone files. A "PGW node name" IE in S3/S10/S16/S5/S8 GTP messages shall be a PGW host name as per clause 4.3.2 of 3GPP TS 29.303[ Domain Name System Procedures; Stage 3 ]  [32] when the PGW FQDN IE is populated from 3GPP TS 29.303[ Domain Name System Procedures; Stage 3 ]  [32] procedures. Specifically, the first DNS label is either "topon" or "topoff", and the canonical node name of the PGW starts at the third label. The same rules apply to "SGW node name" IE on S3/S10/S16 and "SGW-U node name" IE on S5. NOTE 2: The constraint of clause 4.3.2 of 3GPP TS 29.303[ Domain Name System Procedures; Stage 3 ]  format is on populating the IE by 3GPP nodes for 3GPP nodes, the receiver shall not reject an IE that is otherwise correctly formatted since the IE might be populated for a non-3GPP node. An "MME node name" IE and an "SGSN node name" IE in S3 GTP messages indicate the associated ISR node when the ISR becomes active.