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Configure Media Bypass on a Trunk

 

Topic Last Modified: 2012-10-18

Follow these steps if you want to configure a trunk with media bypass enabled. If you want to configure a trunk with media bypass disabled, see Configure a Trunk Without Media Bypass.

Although we strongly recommend that you enable media bypass, before you enable media bypass on a SIP trunk, confirm that your qualified SIP trunk provider supports media bypass and is able to accommodate the requirements for successfully enabling the scenario. Namely, the provider must have the IP addresses of servers in your organization’s internal network. If the provider cannot support this scenario, media bypass will not succeed. For details, see Media Bypass in the Planning documentation.

Note

Media bypass will not interoperate with every PSTN gateway, IP-PBX, and SBC. Microsoft has tested a set of PSTN gateways with certified partners and has done some testing with Cisco IP-PBXs. Certification for SBCs is underway. Media bypass is supported only with products and versions listed on Unified Communications Open Interoperability Program – Lync Server at https://go.microsoft.com/fwlink/p/?LinkId=214406.

To configure media bypass on a trunk

  1. Log on to the computer as a member of the RTCUniversalServerAdmins group, or as a member of the CsVoiceAdministrator, CsServerAdministrator, or CsAdministrator role. For details, see Delegate Setup Permissions.

  2. Open a browser window, and then enter the Admin URL to open the Lync Server Control Panel. For details about the different methods you can use to start Lync Server Control Panel, see Open Lync Server Administrative Tools.

  3. In the left navigation bar, click Voice Routing and then click Trunk Configuration.

  4. On the Trunk Configuration page, 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.
    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 the Enable media bypass check box 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 the Centralized media processing check box 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 refer 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 receiving SIP REFER requests from the Mediation Server and media bypass is enabled, you must also run the Set-CsTrunkConfiguration cmdlet to disable RTCP for active and held calls in order to support proper conditions for media bypass. For details, see the Lync 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 Select Translation Rules, click the rules that 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 in the Deployment documentation for information about defining a new rule.

    • To edit a translation rule that is already associated with the trunk, click the rule name and then click Show details. For details, see Defining Translation Rules in the Deployment documentation.

    • To copy an existing translation rule to use as a starting point for defining a new rule, click the rule name and click Copy, and then click Paste. For details, see Defining Translation Rules.

    • 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. Ensure 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

    Lync 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, ensure 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, ensure the rule that matches any 11-digit number is sorted below the more restrictive rule.

  12. When you are finished configuring the trunk, click OK.

  13. On the Trunk Configuration page, click Commit, and then click Commit all.

    Note

    Any time you create or modify a trunk configuration, you must run the Commit all command to publish the configuration change. For details, see Publish Pending Changes to the Voice Routing Configuration in the Operations documentation.

After you have configured the trunk, continue configuring media bypass by choosing between global media bypass options, as described in Global Media Bypass Options in the Deployment documentation.