Creating a Trunk Configuration
A trunk is a logical connection between the Mediation Server role and a PBX, PSTN gateway, or Internet telephony service provider. Trunk configurations can be scoped so that they apply globally, to a Lync Server site, or to a specific trunk. If these settings vary across devices connected via trunks, a new trunk configuration might be required.
Note
These settings are specific to the signaling and features available across a SIP trunk. Use Topology Builder to create the actual SIP trunk definitions.
A new trunk configuration has the following options:
• Maximum Early Dialogs Supported—This is the number of forked responses the device on the opposite side of the trunk can support for a single SIP invite that is sent to the Mediation Server.
• Encryption Support Level—Required means that Secure Real-Time Transport Protocol (SRTP) must be used to encrypt the media traffic on the trunk, Optional means that the Mediation Server attempts to use encryption if the gateway supports it, and Not Supported means that the media traffic is not encrypted on the trunk.
• Refer Support—This indicates whether the trunk supports Lync sending the SIP refer method for call transfers. Third-party call control (3pcc support) on the trunk is another available choice that can be useful for E911 or operator-based SIP services.
• Enable Media Bypass—Use this option if Lync endpoints should be allowed to send G.711 streams to the opposite side of the trunk. This configuration is highly recommended to reduce processing on the Mediation Server.
• Centralized Media Processing—Use this option if the signaling and media traffic for this trunk terminate at the same IP address. If Media Bypass is enabled, this option must also be selected.
• Enable RTP Latching—RTP latching is an alternative option used to support NAT traversal on a SIP trunk when an SBC or a firewall is incapable of properly fixing the SDP messages for specifying the media IP address.
• Enable Forward Call History—Use this to include any forwarded call history across the trunk. This might be required by SIP trunk providers in forwarding or simultaneous ring situations to validate that the call was originally destined to a number associated with the organization.
• Enable Forward P-Asserted-Identity Data—Use this if the P-Asserted-Identity (PAI) SIP header should be forwarded across the SIP trunk.
• Enable Outbound Routing Failover Timer—This flag places a 10-second limit on responses from the opposite end of the trunk. If the trunk device takes longer than 10 seconds to respond, Lync will try the next available route, or end the call if no more routes are available.
• Associated PSTN Usages—This is used for inter-trunk routing in Lync Server 2013. This parameter specifies which usages are allowed to be called through this trunk.
• Calling Number Translation Rules—New to Lync Server 2013, this is used to manipulate the calling party of numbers dialed through this trunk.
• Called Number Translation Rules—This is used to manipulate the called party of numbers dialed through this trunk.
To create a new trunk, complete the following steps:
1. Open the Lync Server 2013 Control Panel.
2. Click Voice Routing.
3. Click Trunk Configuration.
4. Click New, and then select either Site or Pool scope.
5. Enter a value for the Maximum Early Dialogs Supported field.
6. Select an Encryption Support Level.
7. Select an option for Refer Support.
8. Optionally, check the box for Enable Media Bypass.
9. Optionally, check the box for Centralized Media Processing.
10. Optionally, check the box for Enable RTP Latching.
11. Optionally, check the box for Enable Forward Call History.
12. Optionally, check the box for Enable Forward P-Asserted-Identity Data.
13. Optionally, check the box for Enable Outbound Routing Failover Timer.
14. Click Select and choose any PSTN usages that can be accessed through this trunk via inter-trunk routing.
15. Select any Calling Number Translation Rules and Called Number Translation Rules to be associated with the trunk.
16. Click OK to save the trunk configuration.
Alternatively, the Lync Server Management Shell can be used to create a trunk configuration via the New-CsTrunkConfiguration cmdlet. Several parameters are available only through the Lync Server Management Shell:
• EnableMobileTrunkSupport—A true or false value to indicate whether the trunk is a mobile carrier.
• EnableSessionTimer—A true or false value to indicate whether each session is timed to determine whether it is currently active. Calls exceeding the session timer without a keep-alive response are dropped.
• EnableSignalBoost—A true or false value to indicate whether the opposite end of the SIP trunk should boost the audio volume of packets sent to Lync. This works only if the opposite end of the SIP trunk supports the feature.
• RemovePlusFromUri—A true or false value to indicate whether the Lync Server should remove the plus prefix (+) from any URIs before sending them across this SIP trunk.
• RTCPActiveCalls—A true or false value to indicate whether the trunk sends RTP Control Protocol packets for active calls.
• RTCPCallsOnHold—A true or false value to indicate whether the trunk sends RTP Control Protocol packets for calls placed on hold.
• EnableOnlineVoice—A true or false value to indicate whether the trunk supports Office 365 hosted voice mail for on-premises Lync users.
• EnablePIDFLOSupport—A true or false value to indicate whether the trunk supports the PIDF-LO location information sent by a Lync client for E911 purposes.