This article describes the usage of the Do Not Call (DNC) feature, one of the commonly used in North America region. DNC List contains a set of numbers that should not be allowed to pass through the Softswitch.

There are two DNC Lists configuration:

  • DNC List - blacklist for CLDs (called numbers)
  • DNC CLI List - blacklist for CLI for CLI (calling numbers)

In order to enable either of these features, a request should be sent to the Sippy support team, in turn the request will be resent to the Sippy billing department. Below are instructions on how to manage the DNC List feature once the module is added.


DNC List file requirements

  • file extension could be anything as soon as it's readable text file
  • The DNC file should NOT have BOM (Byte Order Mark) at the beginning.

  • Every line is dedicated to just one number.

  • Only solid numbers are supported, wild-card is not supported.

  • CLI numbers should not consist of any alphanumeric numbers;

  • No separators should be present in number, even comma, dot, or dash.

  • Any non-numeric characters are not counted towards number of digits, therefore both 123,45678901 and 12345678901 would be interpreted as 10-digit number 12345678901.


Make sure that the numbers you place in a given DNC file are exactly the numbers your customers you would like to exclude from calling. Those numbers will be inaccessible from now on.

Example: If your customer's number is 987654321 that you want to be banned, and exactly this number comes to the softswitch, you should add this number in full, with leading 9: ‘987654321’.


The steps of DNC List configuration for CLD numbers:

1. Go to the DNC List* sub-menu under the Routing menu of the Vendors tab. The path is presented in Illustration 1. 

Illustration 1

*lacking the ‘DNC List’ sub-menu means this feature has not been activated yet.

The DNC List file, containing prohibited CLD Numbers, can be uploaded on this page, see illustration 2 below.

Illustration 2


2. Once the file is taken for upload, wait until it's processed. Then, the ‘Uploaded On’ date should be updated accordingly.

3. For accounts that you want to restrict calls with CLDs using this DNC list on Accounts details set the checkbox DNCL Lookup. It is shown on the following Illustration 3.

Illustration 3

4. DNC List is applicable only for Accounts, to make DNCL Lookup checkbox appear for Accounts of subcustomer, DNCL enabled checkbox should be set in Customer's details. It is shown on the following Illustration 4.

Illustration 4

5. Calls with CLDs that are presented in uploaded DNC List file would be dropped with SIP/2.0 470 Consent Needed error code.

Note: enabled DNCL Lookup and DNCL enabled checkboxes would activate both DNC List and DNC CLI List if they are added.


The steps of DNC List configuration for CLI numbers:

1. Go to the DNC CLI List* sub-menu under the Routing menu of the Vendors tab; as it is presented in Illustration 5.

Illustration 5

*lacking the ‘DNC CLI List’ sub-menu means this feature has not been activated yet, or softswitch version is below Sippy 2020

The DNC CLI List file, containing prohibited CLI Numbers, can be uploaded on this page, see illustration 6 below.

Illustration 6

2. Once the file is taken for upload, wait until it's processed. Then, the ‘Uploaded On’ date should be updated accordingly.

3. For accounts that you want to restrict calls with CLIs using this DNC CLI list, set  DNCL Lookup checkbox on Accounts details page. It is shown on the Illustration 3 above.

4. DNC CLI List is applicable only for Accounts, to make DNCL Lookup checkbox appear for Accounts of subcustomer, DNCL enabled checkbox should be set in Customer's details. It is shown on the Illustration 4 above.

5. Calls with CLIs that are presented in uploaded DNC CLI List file would be dropped with SIP/2.0 470 Consent Needed error code.

Note: enabled DNCL Lookup and DNCL enabled checkboxes would activate both DNC List and DNC CLI List if they are added.

Call processing:

1. Authenticate incoming call (either to Incoming DID or to the authentication rule of an account, or using the digest credentials of the account)
2. Apply the number translation if configured on DID pool for call authenticated to Incoming DID
3. Apply the number translation if configured on authentication rule of an account for call authenticated to authentication rule of an account
4. Apply the translation rule of the account
5. Check the resulting translated number in DNCL if DNCL lookup is configured for account that has been authenticated for that call.
6. If no match is found, perform LRN lookup and process the call further.