Number Portability Interworking Support for IAM

When the optional Number Portability Routing Number (NPRN) is present and supported, the SBC uses these procedures to code the ISUP Called Party Number.

For backward compatibility, and to handle deployments where this behavior is not expected (ITU- T1912.5 does not include this requirement), you set the SBC to use this behavior by configuring the portability-method parameter to concatenate within the sip-isup-profile. This attribute allows the SBC to map the different behaviors related to number portability in TS29.163.

In addition, the sip-isup-profile element includes the country-code parameter. When you have configured the portability-method parameter to concatenate and the SBC receives messages that include NPRN in the request URI of an incoming INVITE, the SBC formats the ISUP called number based on the text you configure in the called-party number parameter. The called-party number parameter accepts any string, but is typically configured with a country code. The format (coding) rules are presented below.

Called Party Number

If an NPRN is present as rn param in the request-uri of the incoming INVITE, and an NP Database Dip Indicator (NPDI) parameter is present, the SBC codes the Called Party Number as follows:

• Address Signal—The SBC inserts the following values and format into the IAM, based on the conditions described:
  • If the SIP called number starts with the same country-code as is in the egress sip-isup-profile::country-code:

    The format presented is +CC + NPRN + Called party number (NOA = International)

  • If the SIP called number starts with a different country-code as is in the egress sip-isup-profile::country-code, behave the same as when the portability method is configured as none (transparent), and:

    The format presented is +CC2 + Called party number (NOA = International)

  • If the SIP called number does not start with +:

    The format presented is NPRN + Called party number (NOA = National)

• Nature of address—The SBC inserts the following values into the IAM, based on the conditions described:

  • National, if there is no + in the number (encoded to 0000011).
  • International, if there is a + in the number (encoded to 0000100).
  • Special Number, if there is a phone-context parameter in the request-uri user part, and that number does not start with a + or a 0 (encoded to 1110011).
• Internal Network Number Indicator, with a sole value of 1, indicates routing to an internal network number is not allowed.
• Numbering Plan, which is always ISDN.

Examples of ISUP called party number results, assuming you set the sip-isup-profile, country-code to +33, include:

• If the Request-Uri is sip:[phone] and the rn is 10432;[e-mail]

  Result: 3310432454556677 (NOA=International)

• If the Request-Uri is sip:[phone] and the rn is 10432;[e-mail]

  Result: 44454556677 (NOA=International)

• If the Request-Uri is sip:0454556677 and the rn is 10432;[e-mail]

  Result: 10432454556677 (NOA=National)

• If the Request-Uri is sip:0454556677 and the rn is [e-mail]

  Result: 454556677 (NOA=National)

• If the Request-Uri is sip:[phone] and the rn is [e-mail]

  Result: 33454556677 (NOA=International)

Number Portability Forward Information

The SBC codes this parameter as follows:

• If the NPDI is present, the SBC behaves as follows, in conjunction with the following conditions:
  • NPRN present—The SBC performs a number portability query for the called number, and inserts the ported called subscriber.
  • NPRN absent—The SBC performs a number portability query for the called number, and inserts the non-ported called subscriber.
• If the NPDI is absent—The SBC does not perform a number portability query.