Configuring Direct Inbound Dialing (DID)

Direct Inbound Dialing (DID) refers to a configuration in which public PSTN numbers are assigned to individual users. This means that a user is directly reachable without first calling the company operator (or an auto-attendant) that then transfers the call to a local extension; the external number is called and rings directly at the phones of one or more sipXecs users.

DID handling depends on the connection to the carrier and is different between using a T1 or fractional T1 connection vs. analog lines. With T1 and fractional T1 connections the carrier delivers DNIS (Dialed Number Identification Service) information, which the gateway uses to route an incoming call directly to the respective user with that DID number assigned. Analog lines do not offer that feature.

There is (as if often the case) more than one way to configure how your DID is routed to the correct user(s):

Directing the call by configuration in the gateway

This method is not recommended, since it means that there are multiple components in your system transforming the address; this makes debugging and modifying dial plans more difficult.

Directing the call using sipXecs configuration

The facilities of sipXecs can be used to do any address manipulation needed to direct inbound calls with no transformation in the gateway. The simplest possible gateway configuration is to set the gateway to send all inbound calls to the sipXecs system. The specifics of this vary depending on the gateway, but essentially what you're looking for is to just use the inbound number in whatever form you get from the provider as the user part of the SIP URL, and the sipXecs domain name as the domain part (for example, for the inbound number 9528431212 construct the address sip:9528431212@example.com).

Assigning aliases to destinations

Most kinds of call destinations in sipXecs (including users) can be assigned any number of aliases. To direct calls for a specific DID to some destination, assign the DID value (in whatever form it is sent by the gateway) to the destinations you want as an alias.

For example, if you want the number 9528431212 to ring at Alices phone, and Alice is extension (user) 2207, then assign the alias 9528431212 to user 2207.

AutoAttendants

You can create any number of autoattendants that present callers with whatever choices you select, including transfer to internal extensions. Like other destinations, an autoattendant can be assigned any number of aliases - so to direct a DID to an autoattendant, just add the DID (in the form sent by your provider/gateway) to the autoattendant.

Defining a DID prefix Dialing Rule

When you have blocks of DID numbers, you can usually transform them into internal numbers using a Custom Dialing Plan.

First, identify the DID prefix by determining the constant digits that become the prefix to an internal station number to produce a full DID number. For example, if the format of your DID numbers is 781-854-3nnn, the DID prefix is 7818543. The dialing plan can be used to strip the fixed prefix, and possibly change it to a new internal prefix.

Go to the System>Dial Plans screen.

  1. Select the Add New Rule pulldown
  2. Choose Custom
  3. Choose a name for your rule ("DID" might be a good name)
  4. Select Enabled checkbox
  5. In the Dialed Number setting, enter the DID prefix (7818543) that you want to remove in the Prefix box, and the number of digits from your inbound calls that you want to keep in the pulldown
  6. Do not check any permissions
  7. In the Resulting Call setting, you can either leave the prefix box empty or insert an internal prefix
  8. Append "Matched Suffix" from the drop down
  9. Do not add any gateways (leaving off the gateway causes sipXecs to tranform the address and then re-evaluate how to route it).

Press OK and then Activate your dialing plans.