P-Access-Network-Info SIP Header

The P-Access-Network-Info SIP header is defined in section 4.4 of RFC 3455, Private Header (P-Header) Extensions to the Session Initiation Protocol (SIP) for the 3rd-Generation Partnership Project (3GPP). This header contains information on the access network that the user handset is using to get IP connectivity, and is typically ignored by intermediate proxies between the SBC that adds the header and the SIP proxy that is providing services. The proxy providing services can inspect the header and make use of the information contained there to provide appropriate services, depending on the value of the header. Before proxying the request onwards, this proxy strips the header from the message.

The P-Access-Network-Info header contains an access-type field identifying the radio access technology as received in the RAT-Type attribute.

3GPP-UTRAN — when the RAT- Type AVP value is 1000
3GPP-GERAN — when the RAT- Type AVP value is 1001
3GPP-E-UTRAN — when the RAT- Type AVP value is 1004

The access-type field is followed by the access-info field which identifies the mobile phone cell that provides network access. The location of this cell provides the means to geographically locate connected mobile handsets.

utran-cell-id-3gpp — when the RAT- Type AVP value is 1000
cgi-3gpp — when the RAT- Type AVP value is 1001
utran-cell-id-3gpp — when the RAT- Type AVP value is 1004

The access-info field is followed by an EQUAL sign and a CellID/CGI (Cell Global Identifier) field that contains an octet string which provides the location value contained in the 3GPP-User-Location-Info AVP. The location value can be either an CGI or an Extended CGI (ECGI).

CGI field — when the RAT- Type AVP value is 1000
CGI field — when the RAT- Type AVP value is 1001
ECGI field— when the RAT- Type AVP value is 1004

Examples of P-Access-Network-Info headers are as follows:

If the RAT-Type is UTRAN:

P-Access-Network-Info: 3GPP-UTRAN;utran-cell-id-3gpp=C359A3913B20E

If the RAT-Type is GERAN:

P-Access-Network-Info: 3GPP-GERAN;cgi-3gpp=62F8100005C599

If the RAT-Type is EUTRAN:

P-Access-Network-Info: 3GPP-E-UTRAN;utran-cell-id-3gpp=C359A3913B20E