Section: 13.9.1.2 Format of XCAP Root URI
Content: The XCAP Root URI, as defined in IETF RFC 4825 [94], is an HTTP URI that should have the following format: "http://xcap.<domain>" in which "<domain>" identifies the domain hosting the XCAP server. NOTE 1: The XCAP Root URI does not contain a port portion or an abs path portion of a standard HTTP URI. If a preconfigured or provisioned XCAP Root URI is available then the UE shall use it. When a preconfigured or provisioned XCAP Root URI does not exist then the UE shall create the XCAP Root URI as follows: - The first label shall be "xcap". - The next label(s) shall identify the home network as follows: 1. When the UE has an ISIM, the domain name from the IMPI shall be used (see 3GPP TS 31.103[ Characteristics of the IP Multimedia Services Identity Module (ISIM) application ]  [93]) as follows: a. if the last two labels of the domain name from the IMPI are "3gppnetwork.org": i. the next labels shall be all labels of the domain name from the IMPI apart from the last two labels; and ii. the last three labels shall be "pub.3gppnetwork.org"; b. if the last two labels of the domain name from the IMPI are other than the "3gppnetwork.org": i. the next labels shall be all labels of the domain name from the IMPI; 2. When the UE has a USIM and does not have ISIM, the home network shall be "ims.mnc<MNC>.mcc<MCC>.pub.3gppnetwork.org" where <MNC> and <MCC> shall be derived from the components of the IMSI defined in clause 2.2. If there are only two 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 FQDN of XCAP Root URI. As an example for the case when the UE has ISIM, where the IMPI is "user@operator.com", the overall XCAP Root URI used by the UE would be: "http://xcap.operator.com". As an example for the case when the UE has ISIM, where the IMPI is "234150999999999@ims.mnc015.mcc234.3gppnetwork.org", the overall XCAP Root URI used by the UE would be: "xcap.ims.mnc015.mcc234.pub.3gppnetwork.org". As an example for the case when the UE has USIM and does not have ISIM, where the MCC is 345 and the MNC is 12, the overall XCAP Root URI created and used by the UE would be: "xcap.ims.mnc012.mcc345.pub.3gppnetwork.org"