Caller ID Name, alphanumeric not caller ID numeric, is derived from a database dipping service for all NADP (North American Dialing Plan) numbers. The name is registered by the TN (DID) owner. Example: AT&T wireless cell phone service. To change the Caller Name, you have to call AT&T and have them update your name in the CNAM database.
Telephone companies that receive calls inward subscribe to caller name if that is a service they support for their customers. Services are provided by such companies below:
CNAM is NOT a function of SIP signaling being passed to the PSTN. CNAM is presented to the called party by looking up the CNAM in a CNAM database.
Additional Information:
http://www.voip-info.org/wiki/view/CallerID
Caller ID allows the person being called to see the number (and sometimes the name) of the person calling them, when they have the correct equipment to receive the caller id information. Caller id is often an added value (i.e extra cost) service from your telco. You can usually withhold sending of the caller id on outgoing calls by dialing a special code before the number.
There are many different caller id systems in use around the world.
Note that on the PSTN, CNAM (Caller NAME) data is looked up via caller ID digit information out of a database by the serving CO. It cannot be set by the user.
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