How Caller ID Works

Most phone subscribers are familiar with the concept of Caller ID, also known as CNAM (Caller ID Name). At the very least, most phone subscribers expect to see the phone number associated with an inbound call. Almost every phone, be it a mobile phone, an analog phone, a SIP desk phone, or a softphone, will display as much information as possible when the phone rings. Typically, this is the number of whoever is calling, and often the associated name.

Where does the information come from?

In the North American Numbering Plan Area (NANPA, which includes all of the United States, Canada, Puerto Rico, and the Bermudas) it is the responsibility of the terminating carrier (the carrier of the party you are calling) to provide Caller ID Name services. Caller ID Number is always provided by the originating party -- whoever places the call is responsible for providing a phone number where they can be called back. (At least, this is the intent of the service.)

Many phone carriers subscribe to database services to provide CNAM coverage where they do not have direct subscribers, providing a much higher CNAM delivery success rate. The phone carrier terminating the call will ask the database what name is associated with the calling number.

Where carriers have direct subscribers there is usually no need to ask an external database for line information and the carrier will rely on their own records. Two phone companies can have two different results for the same phone number, depending on where they get their information.

With the number of smaller phone carriers increasing, the ability for subscribers to keep their number via Local Number Portability, and the general disparity between databases, CNAM delivery is not always guaranteed and records are sometimes out of date.

How does Teliax handle Caller ID?

Teliax is able to provide Caller ID name on 100% of calls that remain on our network. We do our best to provide up-to-date information on calls which originate from or terminate to our network.

On every inbound call to our network, we’ll first check and see if we’ve already looked up the name. If we have, we’ll use the cached result. One out of every ten times, we’ll expire the cache and perform a fresh CNAM ‘dip’ -- that is, we check the TNS LIDB (Line Information Database) for any updates or changes to the CNAM associated with the calling number.

On every outbound call from our network, we’ll pass the information sent or set by our subscribers. Often this is a 10-digit number where the subscriber can be reached. For SIP-interconnected carriers we can pass a Caller ID name. For PSTN-based carriers we can only send Caller ID number and it’s once again up to the terminating carrier to perform a lookup.

Teliax is able to provide updated information to the TNS LIDB upon subscriber request. If your caller ID name is showing up incorrectly or if you need to update it, please contact Teliax Support by emailing, or give us a call at 888-4TELIAX (888-483-5429)