Caller ID name is one of the few significant technical differences between international/Canadian and US phone networks.
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, which 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 (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:
1. P-Asserted Identity:
2. Remote-Party ID:
3. 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 receiving end party with no need for a lookup by the receiving carrier.
For the reasons mentioned above, Canadian DIDs should not have CNAM services enabled.