P-Associated-URI
This header is included by registrar in the 200 response to the REGISTER request.
Contains list of associated URIs. Mandatory for registrars which support this RFC.
P-Called-Party-ID
This header is included in INVITE request from proxy to user agent.
Contains destination SIP URI to which initial call was planned.
Used to provided transparent URI to the end user agent in
multiple proxies configuration with call forwarding.
Mandatory for proxies which support this RFC.
P-Visited-Network-ID
In order to enable roaming in home and visited networks.
Proxy servers of visited networks send the ID of the visited network
to the home network while routing INVITE or other request.
Home network proxies use this header to apply special billing rules to the roaming user. Optional.
P-Access-Network-Info
This header is aimed for environments which support different access (Layer 2,3) technologies.
In this header the UA sends parameters of transport network which is used
to deliver SIP packets from UA to the server (proxy).
This information might help the called party to understand the current transport capabilities of
the UA.
P-Charging-Function-Addresses
To support account charging functions the entities in the same
administrative domain may pass this header from one proxy to
another to allow using the same addresses for charging functions.
Charging functions are not defined but only the mechanism to transmit the
URI addresses of such services.
P-Charging-Vector
If charging is managed in a way that multiple SIP proxies must share the same data
for charging then this header might contain globally unique identifiers and
other data which is used by multiple entities in administrative domain for charging functions.