CdPN Number Format Identification

The format of the incoming number and the context surrounding the call factor into both the conditioning of the number for the UDR search and the manner in which the message is treated as a result. The following details about the number must be known:

• Is the call terminating to a subscriber in the home country? (Calls terminating to numbers outside the home country are not subject to IDP Relay because number portability does not cross international boundaries).

• Is the calling subscriber roaming or dialing from inside the home country? (Determines if numbers dialed as national numbers are treated as in-country or out-of-country terminated).

• Was the number dialed with Escape Codes? (These must be deleted for UDR lookup, but might be re-inserted for transmission).

The INAP/CAP CDPN parameter includes a CDPN NAI parameter which indicates the Nature of Address for the dialed digits (International, National, Subscriber, or Unknown). This parameter alone cannot always be relied upon to determine the format of the CDPN. For example,

• The CDPN can contain a National number, but the CDPN NAI may be marked “Unknown”.
• A National number dialed while a subscriber is roaming must be treated differently than a National number dialed while a subscriber is in his/her home country/network. The condition of whether the calling subscriber is roaming or not cannot be determined from the CDPN NAI in the CDPN.

The following additional checks must be applied to the received IDP in order to determine how the message will be treated.

• Escape Codes

  Subscribers are normally required to enter an International Escape Code (IEC) before dialing the digits of an International number. For example, in some countries, the digits 00 must be dialed before dialing an International number.

  Subscribers are also normally required to enter a National Escape Code (NEC) to before dialing long distance National numbers. For example, many countries require a single 0 to be dialed before dialing a National number.

  Escape codes must be removed before IDP Relay performs the UDR lookup, because the numbers in the UDR are always provisioned in International format. When an Escape Code is used, the CDPN NAI will be unknown. Therefore, the presence or absence of an IEC or NEC will indicate whether the number is International or National.

  If a message is received with CDPN NAI = unknown, IDP Relay first checks the leading digits of the number for a match with a provisioned IEC or NEC, and treats the number accordingly. If CDPN NAI = unknown and no match is found on the IEC or NEC, the number is treated as National with no preceding NEC.

• Calling Subscriber Roaming

  Roaming is another factor in the structure of the incoming IDP message. Whether or not the calling subscriber is roaming when the call is placed determines how the message is treated.

  When a subscriber is roaming, all incoming IDP messages generated from calls made by that subscriber are CAMEL Application Part (CAP) rather than INAP message. When a roaming subscriber dials a National Number (number without a Country Code), the call is treated differently that when a non-roaming subscriber dials a National Number. This is because when a subscriber dials a National number while roaming Internationally, it is assumed that the subscriber is attempting to dial a number in the country where he or she is currently roaming, and not in the home country (if the subscriber wishes to dial a number in the home country, it must be dialed as an International number since the subscriber is roaming).

  Because UDR checks are not conducted across International boundaries, calls from a roaming subscriber to a National number are not subject to IDP Relay service. Calls from the same subscriber to a National number when the subscriber is not roaming are subject to IDP Relay service because these numbers are assumed to be terminating in the subscriber's home country, where portability applies. The National number digits could be identical in these two cases, although the actual destination is different.

  For these reasons, the IDP Relay function might need to be able to distinguish between an IDP received for a call generated by a roaming subscriber and one generated by a non-roaming subscriber. The IDP Relay service provides the CgPA Check configuration option to select whether IDP messages generated by roaming subscribers should be subjected to IDP Relay processing, or be routed through standard GTT processing.

  If the CgPA Check configuration option is ON, the roaming status of the calling subscriber is determined by comparing the Country Code in the SCCP CGPA parameter of the IDP message with the provisioned STPOPTS Default Country Code (DEFCC value). (The provisioned DEFCC value corresponds to the home network. If a subscriber is roaming, the CC of the visited MSC will not match the provisioned DEFCC value). If National roaming is allowed, the respective scenarios are treated as if the subscriber is not roaming. A roaming scenario is not detected by the CgPA Check and IDP Relay processing is performed. The the CgPA Check option is ON by default. If the operator wants the IDP Relay feature to process IDP messages generated from roaming subscribers, the CgPA Check option must be turned OFF.

• Call Placed to Country Other than Home Country

  The IDP Relay CgPA Check does not apply if a subscriber dials a number in a country other than subscriber’s home country. The INAP/CAP CdPN Country Code is checked against the provisioned DEFCC value. If a match is not found, it means the subscriber has dialed a number outside his home country and IDP Relay is not required. The message falls through to GTT processing or to another SCCP service.