a P-CSCF generated authorization token. This particular example shows a Policy-Element
generated by "pdf1.home1.net" with credentials "9BV3072". "00" at the end
of the authorization token is required to pad to a multiple of 4 bytes.
P-CSCF1 rewrites the Record-Route header to add the port number negotiated
during the security agreement and the comp=sigcomp parameter to its own SIP URI.