IMS Registration signalling flow —
User not registered
R1-1c. SIP REGISTER request: from P-CSCF1 to I-CSCF1(4 of 22)
P-CSCF1 needs to be in the path for all mobile terminated requests for this user. To ensure this,
P-CSCF1 adds itself to the Path header value for future requests.
P-CSCF1 adds the P-Visited-Network-ID header with the contents of the identifier of P-CSCF1
network. This may be the visited network domain name or any other identifier that identifies the
visited network at the home network.
P-CSCF1 removes the Security-Client header and associated "sec-agree" option-tags prior to
forwarding the request. As the Proxy-Require header is empty, it removes this header completely.
This is the address of P-CSCF1 and is included to inform S-CSCF1 where to route
This header is included to ensure that the recipient correctly handles the Path header. If the
recipient does not support the path header, a response will be received with a status code of
420 and an Unsupported header indicating "path". Such a response indicates a
misconfiguration of the routing tables and the request has been routed outside the IM CN