7.1 Number Conditioning

All DNs and IMSIs in the DN and IMSI databases are stored in international format. To be in international format, the address digits must contain a CC (Country Code), a NDC (Network Destination Code ), and a subscriber number. However, the address digits of the CdPA from the incoming message, which are used in the DN and IMSI lookup, will not always be in international format. Converting the CdPA address digits into international format, so that they can be used in the DN and IMSI lookup, is the goal of number conditioning. The NAI (Nature of Address Indicator) describes the format of the address digits. The NAI types supported by HLRR are:

  • International: the CC, NDC, and subscriber number are all present in the address digits. The address digits do not need any modification.
  • National: the NDC and subscriber number are present in the address digits; the CC is missing and must be added to the address digits.
  • Subscriber: the subscriber number is present in the address digits; the CC and NDC are missing and must be added to the address digits.
  • MLR: IMSI extracted from the MAP layer is used as E.212 without number conditioning. MSISDN extracted from the MAP layer is conditioned to international format (default CC/NDC applied based on NAI) before lookup.

Numbering Plans, DNs and IMSIs

To determine which database to query, HLRR must know if the address digits of the CdPA from the incoming message contain a DN or an IMSI. The numbering plan describes the contents of the address digits. The numbering plans supported by EXHR are:

  • E.164: the address digits contain a DN, perform number conditioning on the address digits and query the DN database with the conditioned number.
  • E.212: the address digits contain an IMSI, perform number conditioning on the address digits and query the IMSI database with the conditioned number.
  • E.214: the address digits contain a MGT, perform number conditioning on the address digits, then convert the conditioned number to an E.212 number, then query the IMSI database with the converted number.