What it does

The dial plan enforcement (DPE) service ensures that a subscriber has dialed a valid number before allowing a call to proceed.

Number analysis

The service works by confirming that the length of the dialed number is within an expected range. The allowed range can vary based on prefixes that the service detects on the number.

For example, the configuration for the service might specify that:

  • a number starting with 087 can be between 4 and 9 digits long (not including the prefix itself), and

  • all other numbers must be between 4 and 7 digits long.

In this case:

  • 12345678 would be rejected by the DPE service for having more than 7 digits, but

  • 08712345678 would be allowed since the 087 prefix means the number can have up to 9 digits after the prefix.

The service may be configured to detect any number of different prefixes with different ranges for each one. If a single number has multiple potential prefix matches, the service will choose the longest matching prefix.

There is a special case for numbers that are in international format. If one begins with either the configured national-prefix or the configured international-prefix, then the DPE service is bypassed. All other international format numbers will be subject to the same enforcement checks as non-international numbers. See the Number normalization section for information about configuring the national and international prefixes.

Call handling

If a number is allowable according to the DPE service configuration, then the call proceeds as normal.

If a number is rejected, then the call will be refused with a SIP error response. It is possible to configure an announcement to play to the calling party when this happens.

Interactions with other services

Vertical service codes (VSC)

If the VSC service modifies the dialed number by stripping certain prefixes from it, the DPE service will do its analysis on the modified version of the dialed number.


Currently, the declarative configuration for the DPE service is only available through low-level overrides, which require the guidance of Metaswitch support.

To configure the service, contact your Metaswitch customer care representative.

Note Full declarative configuration support for this service may become available in a later version.
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