What is Calling Line Identity?

15 December 2010 |


Calling Line Identity (CLI) is a method by which inbound calls made to a business or individual can be identified by their number of origin and, in some cases, the name of the person or organisation that is associated with the number.

The phone number of the person calling is displayed on the recipient’s telephone screen, or on a separate device. Caller ID was originally developed for the Public Switched Telephone Network (PSTN) system. CLI can be used for a number of reasons, but most businesses make use of the inbound caller’s data as part of a statistics gathering process, or in order to screen inbound calls and respond to them appropriately.

CLI can be used on analogue telephone services and digital mobile services but is also widely available for network-based VoIP calls.

Why is CLI important for wholesale carriers?

Mobile operators are turning to international wholesale voice carriers for this increasingly important – but technically demanding – mobile-to-mobile traffic. Even though it is not impossible to set up direct connections and agreements with the 700 plus mobile operators, a single connection to an international voice carrier can be less complicated and more cost effective.

For the international voice carrier this situation presents them with not only the opportunity to improve revenues and their bottom line but also the challenge of addressing the need to have more control over quality expectations or the customer experience. Global roaming traffic is growing fast and customers demand seamless signalling between the mobile networks with high expectations of quality of service.

How do carriers test CLI and verify quality of service?


Currently, there are very few complete systems in the market for carrying out automated test calls. Mobile operators mainly use such systems as a need to ensure premium customer experience and quality at much better margins. International wholesale carriers either use some kind of less sophisticated self-developed system or have departments dedicated to manually making test calls into countries and asking if the CLI is being transmitted.

One eastern European operator where the state has a controlling stake utilises the Embassy and consulate staff located throughout the world, in order to obtain confirmation that their routed call is displaying CLI. This is obviously not a very effective way of dealing with customer complaints about quality of service, especially when millions of minutes are being terminated.

How can CLI impact on revenue for wholesale carriers?

In the wholesale arena, CLI presentation is an important feature, along with requesting higher quality of voice. Indeed, the provision of CLI is seen as a quality parameter. The advances of smart phones and PDAs have forced many operators to think hard about CLI presentation.

Carriers who are able to guarantee CLI presentation often attract higher premiums, allowing them to increase revenue via their service level agreements when they can consistently provide this service.

It is in the interest of the clients of wholesale carriers which offer this service to ensure that they have the appropriate tools at their disposal to check the quality of service and CLI presentation. When CLI is not presented, or when the presentation of CLI is inconsistent during a contracting period, the client can penalise the provider on SLA failures.

What is Calling Line Identification Restriction?

Calling Line Identification Restriction (CLIR) is a customer-initiated mechanism to prevent the CLI from being revealed at the termination point.

Normally, CLIR is transmitted in the network and the terminating provider/ switch identifies the CLI restriction flag and prevents display at termination. This is not a network and provider behaviour. Typically, users do not restrict their numbers, although this feature is readily available in many mobile handsets where users can bar the broadcasting of their own number. Someone who is forwarding calls from a fixed line to a mobile may not want callers to be able to identify their mobile phone number in order to preserve their privacy.

The restriction of CLI can limit the features available on the new PDA and smart phones, however; this could include displaying a library picture of the caller, or changing the phone’s ringtone to indicate the identify of the caller. As such features now play an increasingly significant role in our day-to-day lives, the restriction of CLI is regarded by some as an escape mechanism by advocates of the feature, but is seen as a hindrance by the majority of others.

What impact has the Truth in Caller ID Act had on carriers?

The impact of the Truth in Caller ID Act of 2010 is clear at the retail and end customer level. Individuals and companies can no longer masquerade their calls under a different number, or present an ordinary number in one country where the actual call originated somewhere else.

The Truth in Caller ID Act is a US initiative, and is not accepted as an established practice in the rest of the world. However, it makes sense to adopt such a regime in the international wholesale market.

Some providers operate what they refer to as ‘CLI stuffing’ practice, where the originating CLI is replaced with a random number, thus hiding the origin of the call. As this act is implemented and accepted by international suppliers, CLI presentation will become the norm, and will ensure that, under the guise of the CLI guarantee, some carriers do not attempt to absolve their contractual service level agreements and obligations.


CLI Verification Testing Systems

Ascom Systems & Solutions provide a unique internationally installed test system for fixed, 2, 2.5 and 3G mobile services. For further information, contact Keith Shillingford, International Sales Manager, Ascom Deutschland GmbH Systems & Solutions at: shillingford@ascom-ac.de