back to TS 24.228
- Request-URI: In the case where the Request-URI of the incoming INVITE request to S-CSCF contains a TEL-URL, it has to be translated to a globally routable SIP-URL before applying it as Request-URI of the outgoing INVITE request. For this address translation the S-CSCF uses the services of an ENUM-DNS protocol according to RFC 2916, or any other suitable translation database.
- As S-CSCF1 does not know whether the I-CSCF at home2.net is a loose router or not, it does not introduce a Route header.
- P-Asserted-Identity: S-CSCF1 inserts the corresponding TEL URL to the P-Asserted-Identity header in order that the TEL URL is known to the destination network in case the INVITE is forwarded to a MGCF.
- P-Charging-Vector: S-CSCF1 adds the identifier of its own network to the originating Inter Operator Identifier (IOI) parameter of this header.
- I-CSCF2 sends a query to the HSS (the public user identity is provided in the Request-URI) to find out the S-CSCF of the called user. The HSS responds with the address of the current S-CSCF for the terminating subscriber.