AdminGuide:Service:CLIR

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Calling Line Identification Restriction (CLIR)

Description

This service lets a user hide their caller ID when making a call. This way the called party will not be able to obtain the number of the caller, even if their device is CLIP (Calling Line Identification Presentation) enabled.

Obscuring caller ID is not always possible and may be subject to regulatory restrictions. Calls to emergency services will ignore CLIR through the Calling Line Identification Restriction Override (CLIRO) service, and some types of calls (e.g. commercial/marketing calls) are not allowed to hide the identity of the calling party.

This service is applied to calls between extensions as well as outbound calls. In order for the service to function correctly for outbound calls, outbound gateways must be configured correctly and/or the VoIP provider must support CLIR.

The service can be enabled/disabled on a call-by-call basis, and the default behavior can be configured for each extension.

The user can obscure their caller ID by dialing the CLIR "Setup" code (by default *671) followed by the number to call.
If the user wishes to show their caller ID, they must dial the CLIR "Remove" code (by default *670) followed by the number to call.

Configuration

In order to use the service, it must be enabled in the numbering plan (where you can also edit the service codes).

Whether the service is enabled or disabled, as well as the default behavior, must be specified for each extension (this can be done through extension templates). Other than the default behavior for calls between extensions and calls to external numbers, the settings for each extension include the option to hide the caller ID if the calling device sends a Privacy: id SIP Header.

Interoperability

When CLIR is enabled, SIP signaling is modified as follows:

• the user part of the From URI is replaced with anonymous (e.g. sip:anonymous@<telephone_ip_address>:<telephone_port>);
• the user part of the Contact Header is replaced with anonymous (e.g. sip:anonymous@<ip_address_registrar>:<registrar_port>);
• the Privacy: id SIP header is added.

Calls between extensions do not require additional configuration, while outbound calls might, depending on the type of outbound line.

• VoIP Provider

Even if CLIR is enabled, it is still necessary to send the identity of the calling party to the provider. If this doesn't happen, the provider will normally reject the outbound call. This information can be sent through P-Asserted-Identity Header or Remote-Party Header.

These headers must be enabled in the configuration of the outbound trunks (Gateways and VoIP Domains -> Trunk). The accepted format for the headers is usually the one suggested in the configuration page. If there are issues, you should check the required configuration with your service provider.

To prevent these headers from being overwritten, it is necessary to disable COLP in the outbound trunk configuration.