CNAM(Caller ID Name)

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Overview

CNAM(Caller ID Name) 내용 정리.

Basic

In the US, just the Caller ID number is passed between carriers. When the service provider of the calling destination receives the call, it looks up the Caller ID number in the CNAM database if the end subscriber pays for the Caller ID name service. This lookup provides the registered Caller ID name, that is then supplied to the end user. There is a charge for each CNAM database "dip" of around half a cent that goes from the telco that does the lookup to the telco that registered the number in the CNAM.

The Canadian process was defined by Stentor(https://en.wikipedia.org/wiki/Stentor_Alliance) in 1993 when the Caller ID name feature was first introduced. In Canada, CNAM storage is nonexistent because there are no CNAM storage databases. The CNAM is pulled from the display name found in the SIP signaling. It is pulled from one or all of the following fields.

  • P-Asserted Identity
  • Remote-Party ID
  • From

The point to remember for Canada CNAM, the Caller ID name is sent by the calling party along with the number, and is passed through to end receiving party with no need for a lookup by the receiving carrier.

USA

In the U.S., there are several CANM databases that have a record of every US number and the CNAM associated with the number. When a CNAM listing is enabled on a U.S. number, the CNAM details are inserted into the relevant database.

When a call is placed between two U.S. numbers, the carrier who receives the call will check one of the databases to get the CNAM associated with the number. The carrier will pass the call along with the CNAM to the called party.

Canada

In Canada, there is no national CNAM database. Instead, the CNAM information is passed in the appropriate SIP headers. The SIP headers are:

  • From
  • P-Asserted-Identity

만약 FROM 헤더가 아래와 같이 주어졌다면, 다음과 같이 파싱된다.

FROM: "name" <sip:destination_number@test.com>
  • Caller Name: name
  • Caller Number: destinaioin_number