Additional ISUP IAM Generation Functions
Additional IAM generation functions include interworking Clearmode calls, user-to-user headers, and PANI headers. These functions are specified by TS 29.163.
Clearmode Calls
While interworking a SIP INVITE message containing request for Clearmode call setup, the SBC adds the User-Service-Information parameter to the IAM message it generates. The applicable User-Service-Information subfield parameter values include:
- Coding Standard— ITU-T standardized coding (00)
- Information transfer capability—Unrestricted digital information (01000)
- Transfer mode—Circuit mode (00)
- Information transfer rate— 64 kbits/s (10000)
User to User Header Interworking
The SBC interworks user-to-user headers if the received SIP INVITE contains a user-to-user header field with the following:
- A purpose header field parameter set to isdn-uui, (or without a purpose parameter)
- An encoding header field parameter set to hex (or without an encoding parameter)
- A "content" header field parameter set to "isdn-uui" (or without a "content" parameter)
If all of the above are true, the SBC maps the content of the uui-data field to the protocol discriminator and user information parameters of the user-to-user information element as it generates the IAM message.
The applicable user-to-user Information subfield parameter values include:
- user-to-user information element identifier—0100000
- protocol discriminator—Convert the received User-to-User header to ASCII and add the first two nibbles.
- user information—Remove the first two nibbles (protocol discriminator) from the received user-to-user header and convert all the digits from hex to ASCII.
PANI Header Interworking
The SBC adds the location-number parameter to the IAM message if the SIP INVITE contains a P-Access-Network-Information (PANI) header that uses the format shown in the example below.
P-Access-Network-Info:GSTN;operator-specific-GI="5522300";network-provided
The SBC follows these rules while interworking the PANI to location number:
- Only interwork PANI headers that have an operator-specific-GI parameter.
- Only interwork PANI headers with an operator-specific-GI parameter that contain a sequence of digits.
- If multiple instances of PANI are present, only interwork the instance that has the access network specific component that contains a network-provided parameter.
- If there are multiple instances that contain a network-provided parameter, use the first.
- If none of the PANIs are network-provided, interwork the first PANI that is a GSTN type.
The SBC interworks location number subfields as follows:
- Nature of address indicator—National (significant) number (national use) (0000011)
- Internal Network Number indicator—Routing to internal number not allowed (1)
- Numbering Plan indicator—ISDN (001)
- APRI:
- If the Privacy header is present with a value of header, use Presentation Restricted (01)
- Otherwise, use Presentation Allowed (00)
- Screening Indicator:
- If the network-provided parameter is present, use Network Provided (11)
- Otherwise, use user provided, verified and passed (01)
- Address Signal—Value of operator-specific-GI