Outbound fax calls through DMG fail with Q.931 cause #50 - requested facility not subscribed
- Nathaniel Halbrooks
Symptom
On outbound fax calls initiated by a fax server through the Dialogic 2000 Media Gateway (DMG2000), the DMG2000 logs will show a failure with Q.931 cause #50 - requested facility not subscribed.
Reason for the issue
A typical reason for Q931 cause #50 is that the user has requested a supplementary service which is implemented by the equipment which generated this cause but the user is not authorized to use. An example is where a switch connected to the DMG2000 receives information for calling or called name/number being dialed and interprets it is for another service rather than ISDN. Formats for the calling or called named/number vary from service provider to service provider. If the format matches what the service provider expects, then there the call will be placed properly. If the format does not match the format the service provider expects, then the call may fail with a Q.931 caused code.
Procedure
The following is the two step verification to check for the cause of the issue:
1. Calling or Called Number
Supported formats can vary from service to service provider. Some service providers expect to see 7 digits, some 10, and others 11. Also one needs to check if there any special characters (+ . , etc.) included in the number that might not be accepted by the service provider. The CPID manipulation section under the routing table provide a facility to alter these numbers before they are sent out to the connected switch. More details about CPID manipulation can be obtained using the table below:
2. Calling or Called Name
Some service providers do not accept any calling or called name. It is possible that the calls initiated by the fax server have a calling or called party name that can be a cause for this issue. To address this issue, the calling or called party name can be set to blank by editing the CPID manipulation section under the routing table. Setting it to blank will send the calls without a calling or called party name. An example of this is seen in the screenshot below:
