Trunk Configuration

A trunk is a logical connection between the Mediation Server role and a PBX, PSTN gateway, or Internet Telephony Service Provider. The trunk settings apply to any gateway the site or pool is associated with, so if these settings vary across gateways, a new pool might be required for each unique set. Creating a new trunk configuration has the following options:

• Scope—A trunk can either be scoped so that it applies to entire Lync Server site or it can be restricted to only a specific Front End pool. A global trunk configuration also exists.

• Maximum early dialogs supported—This value is the number of forked responses the opposite end of the trunk can support in a single SIP INVITE that it sends to the Mediation Server.

• Encryption support level—Required means Secure Real-Time Transport Protocol (SRTP) must be used to encrypt the media traffic on the trunk, Optional means the Mediation Server attempts to use encryption if the gateway supports it, and Not Supported means the media traffic is not encrypted on the trunk.

• Enable media bypass—Use if endpoints are allowed to communicate directly with the opposite end of the trunk. This configuration is highly recommended to reduce processing on the Mediation Server.

• Centralized media processing—Use if the signaling and media traffic for this trunk terminate at the same IP address. If using Media Bypass is enabled, this option must also be selected.

• Enable refer support—Use if the trunk endpoint supports receiving SIP REFER requests from the Mediation Server.

To create a new trunk, complete the following steps:

1. Open the Lync Server 2010 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. Optionally, check the box for Enable media bypass

8. Optionally, check the box for Centralized media processing.

9. Optionally, check the box for Enable referrer support.

10. Click OK to save the trunk configuration. Translation rules can be applied at a later time after they are created.

Alternatively, the Lync Server Management Shell can be used to create a trunk configuration:

New-CSTrunkConfiguration –Identity <Name> -ConcentratedTopology
<$True|$False> -EnableBypass <$True|$False> -EnableReferSupport
<$True|$False> -MaxEarlyDialogs <$True|$False> -OutboundTranslationRulesList
<Collection of translation rules> -SRTPMode <Required|Optional|NotSupported>

There are also a number of parameters configurable for a trunk that are not exposed in the Lync Control Panel. These parameters can be set using only the New-CSTrunkConfiguration or Set-CSTrunkConfiguration cmdlets:

• EnableMobileTrunkSupport—True or false value to indicate whether the trunk is a mobile carrier.

• EnableSessionTimer—True or false value to indicate if each session is timed to determine whether it is currently active or not.

• EnableSignalBoost—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 feature works only if the opposite end of the SIP trunk supports the feature.

• RemovePlusFromUri—True or false value to indicate whether the Lync server should remove the plus prefix (+) from URIs before sending them across this SIP trunk.

• RTCPActiveCalls—True or false value to indicate whether the trunk sends RTP Control Protocol packets for active calls.

• RTCPCallsOnHold—True or false value to indicate whether the trunk sends RTP Control Protocol packets for calls placed on hold.