The registrar retrieves these associated URIs from the HSS during the registration
process and sends them to the device that is registering so that it may save in its cache the
other URIs it can answer. A complete description of this process is found in Chapter 5.
P-ASSOCIATED-URI: travisruss@aol.com; russell@tekelec.com
P-Called-Party-ID When an INVITE is forwarded to another address for a registered
subscriber, it is impossible for the user device to determine for what registration (or
what identity??”personal, business, etc.) the original session was intended. This is because
the original INVITE contains the called party within the request-URI, and when
the session is forwarded by a proxy, the request-URI is changed to reflect the new
destination.
For this reason the P-CALLED-PARTY-ID header was added as an extension to the
SIP protocol. This allows the proxies to insert the original identity that was ???dialed??? or
called, allowing the receiving device to treat the call accordingly.
For example, if the P-CALLED-PARTY-ID reflects that the original session request
was sent to the user??™s business URI or identity but is being received on his or her personal
identity, then the device could apply special ringing or send the call directly to
voicemail, based on call treatment defined by the user.
P-CALLED-PARTY-ID: sip:russell@tekelec.com
P-Charging-Function-Address This is another header that was added by the 3GPP specifically
for use within the IMS.
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