[SIPForum-discussion] What are the uses of P-Preferred-Identity??
Paul Kyzivat
pkyzivat at alum.mit.edu
Mon Aug 17 15:49:26 UTC 2015
On 8/16/15 2:28 AM, pendyala syam wrote:
> Hi All,
>
> As far I understand, P-Preferred-Identity will be shown as caller
> display name in callee UI. When SIP already have From header which
> carriers the caller identity, why is this P-Preferred-Identity header
> required? Why can't we use From header to show caller display name at
> callee UI?. Is there any added advantage of this header. Some body
> please explain. Thanks in advance.
The callee should not even *see* P-Preferred-Identity!
The callee may get P-Asserted-Identity. Depending on the envirnment in
which it operates, it may choose to display that rather than the
contents of From.
P-Preferred-Identity and P-Asserted-Identity are used in some some
networks (e.g. 3gpp IMS) based on a trusted core network.
In some cases a device wishes to register and authenticate once to the
core network but then have multiple identities enabled by that
registration. In that case, P-Preferred-Identity is a way for the device
to indicate which of those identities is to be used on a particular
call. The core network can then verify if the caller is authorized to
use that identity. If so, it removes the P-Preferred-Identity and adds a
P-Asserted-Identity.
The recipient depends on the core network having authenticated the
caller and having only added P-Asserted-Identity when authorized.
This is all used because the From header is not supposed to be altered
between caller and callee.
Hope this helps.
Thanks,
Paul
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