2.2.5 Referred-By Header Field Extensions

  • Article

This protocol extends the syntax of the ReferredBy header field defined in [RFC3892] section 3. The extensions to the original ABNF, as defined in [RFC5234], are as follows.

 Referred-By  =  ("Referred-By" / "b") HCOLON referrer-uri
                   *( SEMI (referredby-id-param
                          / ms-identity-param
                          / ms-identity-alg-param
                          / ms-identity-info-param
                          / ms-identity-cookie-param
                          / ms-referee-uri-param
                          / generic-param) )
 ms-identity-param = "ms-identity" EQUAL ms-identity-token
 ms-identity-token = quoted-string
 ms-identity-alg-param = "ms-identity-alg" EQUAL token
 ms-identity-info-param = "ms-identity-info" EQUAL ms-identity-info-val
 ms-identity-info-val = quoted-string
 ms-identity-cookie-param = "ms-identity-cookie" EQUAL 
                             ms-identity-cookie-token
 ms-identity-cookie-token = quoted-string
 ms-referee-uri-param = "ms-referee-uri" EQUAL DQUOTE SIP-URI DQUOTE

EQUAL, generic-param, quoted-string, and token are defined in [RFC3261] section 25.1.

Referrer-uri and referredby-id-param are defined in [RFC3892] section 3.

The ms-referee-uri-param parameter used in the protocol between the SIP protocol client and the server is documented in section 3.2.4.4. Other extension parameters are used only for communications between SIP servers and have the following definitions.

  • ms-identity-param: A token that cryptographically verifies the identity of the referrer within the context of the referred call.

  • ms-identity-alg-param: A token that specifies the cryptographic algorithm used for the ms-identity-param computation.

  • ms-identity-info-param: Information about the server that performed the ms-identity-param computation.

  • ms-identity-cookie-param: Cryptographic token that verifies the content of the ReferredBy header field.