Via:
The P-CSCF adds the port number negotiated during the security agreement and the
comp=sigcomp parameter to its Via header.
Record-Route:
The P-CSCF adds the port number negotiated during the security agreement and the
comp=sigcomp parameter to its own URI.
P-Media-Authorization:
A P-CSCF generated authorization token. This particular example shows a Policy-Element
generated by "pdf1.home1.net" with credentials "31S14621".