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 P-CSCF1 URI and is included to inform S-CSCF1 where to route terminating requests.
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