[VoiceOps] Caller-ID: SIP From vs. P-Asserted-Identity

Jay Hennigan jay at west.net
Mon Jul 23 17:08:04 EDT 2012

Question for the experts:

We have a scenario where a SIP user originates a call to the PSTN (not
9-1-1) with a SIP From: header containing one DID and
P-Asserted-Identity showing a different DID.

We expect the carrier to use the P-Asserted-Identity for billing and
recordkeeping but send the SIP From: out as the CLID to be displayed to
the called party.

Typically this is done in a call center type scenario where an agent
wants the CLID to display the main number of the agent  pool and not the
specific DID of the agent.  Another scenario is a customer PRI-based PBX
that hairpins inbound calls back out to a traveling user and wants to
preserve the original caller's information.

One of our terminating carriers uses the P-Asserted-Identity as the
displayed CLID and not the SIP From:.  I feel that this is not correct.

Numbers have been changed to protect the guilty...

TO: <sip:8055550123 at www.xxx.yyy.zzz;user=phone>

FROM: "Fred
Flintstone"<sip:+18055550199 at www.xxx.yyy.zzz;user=phone>;tag=1689985881-1343063740200-
P-Asserted-Identity: "Fred
Flintstone"<sip:+18055550177 at www.xxx.yyy.zzz;user=phone>

TIME/DATE: Mon Jul 23 17:15:39 2012  (GMT)

RESULT: Called party (8055550123) is seeing 8055550177 as calling
party's caller ID instead of 8055550199

Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
Impulse Internet Service  -  http://www.impulse.net/
Your local telephone and internet company - 805 884-6323 - WB6RDV

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