I my experience it means that the identity of the connected party has changed.

say you have a SIP gateway to some non-SIP network.
If a transfer occurs inside the network then the SIP
endpoint could become connected to a different user.

The SIP UA will update the P-Preferred-Identity

from RFC 3325:
9.2 The P-Preferred-Identity Header

   The P-Preferred-Identity header field is used from a user agent to a
   trusted proxy to carry the identity the user sending the SIP message
   wishes to be used for the P-Asserted-Header field value that the
   trusted element will insert.

LATER IN THE SAME SECTION...
   It is worth noting that proxies can (and
   will) remove this header field.


Then I think the proxy will remove P-Preferred-Identity and
replace it with a P-Asserted-Identity to propagate the new identity.


>From RFC 3325:
9.1 The P-Asserted-Identity Header

   The P-Asserted-Identity header field is used among trusted SIP
   entities (typically intermediaries) to carry the identity of the user
   sending a SIP message as it was verified by authentication.

LATER IN THE SAME SECTION...
   It is worth noting that proxies can (and
   will) add and remove this header field.


regards

Attila




-----Original Message-----
From: [email protected] on behalf of Jyoti Singhal
Sent: Thu 10/03/2011 05:29
To: [email protected]
Subject: [Sip-implementors] Significance of different PAID header inRe-INVITE
 
Hi All,

I need to know is there any significance of a modified PAID header in
Re-INVITE.

With Regards,
Jyoti
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