1. Open Communications Server Control Panel.

2. In the left navigation bar, click Voice Routing.

3. Click the Trunk Configuration tab.

4. Use one of the following methods to configure a trunk:

   • Double-click an existing trunk (for example, the Global trunk) to display the Edit Trunk Configuration dialog box.
     
     
   • Click New, and then select a scope for the new trunk:
     
     
     • Site trunk: Choose the site for this trunk configuration from the Select a Site dialog box, and then click OK. Note that if a trunk has already been created for a site, the site does not appear in the Select a Site dialog box.
       
       
     • Pool trunk: Choose the service for this trunk configuration (for example, a PSTN gateway at a specified site) from the Select a Service dialog box, and then click OK. Note that if a trunk has already been created for a service, the service does not appear in the Select a Service dialog box.
       
       

   Note:
   After you select the trunk’s scope, it cannot be changed.

   Note:
   The Name field is prepopulated with the name of the trunk’s associated site or service and cannot be changed.

5. Specify a value in the Maximum early dialogs supported box. This is the maximum number of forked responses a PSTN Gateway, IP-PBX, or ITSP Session Border Controller can receive to an INVITE that it sent to the Mediation Server. The default value is 20.

   Note:
   Before you change this value, consult your service provider or equipment manufacturer for details about the capabilities of your system.

6. Select one of the following Encryption support level options:

   • Required: Secure Real-Time Transport Protocol (SRTP) encryption must be used to help protect traffic between the Mediation Server and the gateway or PBX.
     
     
   • Optional: SRTP encryption will be used if the service provider or equipment manufacturer supports it.
     
     
   • Not Supported: SRTP encryption is not supported by the service provider or equipment manufacturer and therefore will not be used.
     
     

7. Select Enable media bypass if you want media to bypass the Mediation Server for processing by the trunk peer.

   Important:
   For media bypass to work successfully, the PSTN Gateway, IP-PBX, or ITSP Session Border Controller must support certain capabilities. For details, see “Media Bypass” in the Planning documentation.

8. Select Centralized media processing if there is a well-known media termination point (for example, a PSTN Gateway where the media termination has the same IP as the signaling termination). Clear this check box if the trunk does not have a well-known media termination point.

   Note:
   Media bypass is only supported if this option is selected.

9. If the trunk peer supports receiving SIP REFER requests from the Mediation Server, select the Enable transfer support check box. Clear the check box if the trunk peer does not support receiving SIP REFER requests from the Mediation Server.

   Note:
   If you disable this option while the Enable media bypass option is selected, additional settings are required. If the trunk peer does not support transfer requests from the Mediation Server, run the Set-CSTrunkConfiguration cmdlet. For more information, see the Communications Server Management Shell documentation.

10. (Optional) Associate and configure translation rules for the trunk:

    • To choose one or more rules from a list of all translation rules available in your Enterprise Voice deployment, click Select. In the Select Translation Rules dialog box, highlight the rules you want to associate with the trunk and then click OK.
      
      
    • To define a new translation rule and associate it with the trunk, click New. See Defining Translation Rules for information about defining a new rule.
      
      
    • To edit a translation rule that is already associated with the trunk, highlight the rule name and click Show details. See Defining Translation Rules for information about editing a rule.
      
      
    • To copy an existing translation rule to use as a starting point for defining a new rule, highlight the rule name and click Copy, and then click Paste. See Defining Translation Rules for information about editing the copy.
      
      
    • To remove a translation rule from the trunk, highlight the rule name and click Remove.
      
      

    Warning:
    Do not associate translation rules with a trunk if you have configured translation rules on the associated trunk peer because the two rules might conflict.

11. Make sure the trunk’s translation rules are arranged in the correct order. To change a rule’s position in the list, highlight the rule name and then click the up or down arrow.

    Important:

    Communications Server traverses the translation rule list from the top down and uses the first rule that matches the dialed number. If you configure a trunk so that a dialed number can match more than one translation rule, make sure the more restrictive rules are sorted above the less restrictive rules. For example, if you have included a translation rule that matches any 11-digit number and a translation rule that matches only 11-digit numbers that start with +1425, make sure the rule that matches any 11-digit number is sorted below the more restrictive rule.

After you have configured the trunk, continue configuring media bypass by choosing between Global Media Bypass Options.

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