Section: 14.7 W-APN
Content: The W-APN is composed of two parts as follows: - The W-APN Network Identifier; this defines to which external network the PDG is connected. - The W-APN Operator Identifier; this defines in which PLMN the PDG serving the W-APN is located. The W-APN Operator Identifier is placed after the W-APN Network Identifier. The W-APN consisting of both the Network Identifier and Operator Identifier corresponds to a FQDN of a PDG; the W-APN has, after encoding as defined in the paragraph below, a maximum length of 100 octets. The encoding of the W-APN shall follow the Name Syntax defined in IETF RFC 2181 [18], IETF RFC 1035 [19] and IETF RFC 1123 [20]. The W-APN consists of one or more labels. Each label is coded as a one octet length field followed by that number of octets coded as 8 bit ASCII characters. Following IETF RFC 1035 [19] the labels shall consist only of the alphabetic characters (A-Z and a-z), digits (0-9) and the hyphen (-). Following IETF RFC 1123 [20], the label shall begin and end with either an alphabetic character or a digit. The case of alphabetic characters is not significant. The W-APN is not terminated by a length byte of zero. For the purpose of presentation, a W-APN is usually displayed as a string in which the labels are separated by dots (e.g. "Label1.Label2.Label3"). The W-APN for the support of IMS Emergency calls shall take the form of a common, reserved Network Identifier described in clause 14.7.1 together with the usual W-APN Operator Identifier as described in clause 14.7.2.