Remote Audio/Video Edge Server Configuration in Lync Server 2010


Have you come across a scenario in which remote users were unable to connect to audio/video from their Lync client?  The first thing to look for in this scenario is correct configuration of the edge pool within Topology Builder.

Author: Jazzy Doakes

Publication date: April 2011

Product version:  Lync Server 2010

You may come across the issue of audio/video failing for remote users.  In this situation, when a remote user attempts to join a Lync meeting, the join is successful, but the audio fails when it attempts to connect to the conference. The main reason for this failure is that there is an incorrect configuration in the Edge pool topology.

When configuring the edge pools in Topology Builder, the correct NAT-enabled, public IP address to use is not clearly stated when separate IP addresses are being used for each edge service. Most people add the public IP address for SIP Access when this should be the public IP address for the Audio/Video Edge Service.

When configuring network address translations (NAT) for the edge pool, the wizard asks for the public IP address of the Audio/Video Edge Service. 

Figure 1. NAT configuration on the Edge pools properties points to the public IP address of the Audio/Video Edge Service.

Summary

Audio/video will fail for remote users if the NAT IP address for the Edge pool does not point to the public IP address for the Audio/Video Edge Service.

This NAT IP address is needed to ensure communication with the remote external client, which may be located behind a firewall, and the internal client within the corporate environment, which is also behind a firewall.

Traversal Using Relay NAT (TURN) and Session Traversal Utilities for NAT (STUN) are protocols that are used for audio, video, and desktop sharing data transfer, and for clients and servers to obtain STUN candidates and allocate TURN candidate transport addresses on the A/V Edge Service for traversal of NATs and firewalls. STUN and TURN produce the candidates (on which ICE then performs connectivity checks) to find the preferred route for data transmission across the A/V Edge Service.

Internet Connectivity Establishment (ICE) is used to traverse NATs and firewalls with audio, video, and desktop sharing data.

If the setting is not correctly configured, audio, video, or desktop sharing for remote users will not be available.

Another Scenario

What about a Microsoft hosted meeting with a federated partner who has enabled only IM federation? Depending on your client usage, this may fail, because ports are not open, and thus you won't be able to connect to the Audio/Video or Sharing session. The solution is to force Lync Web App. For more information on this scenario, check out Launching Lync Web App, by Jens Trier Rasmussen .

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Keywords: remote audio/video, Edge Server, Lync Server 2010, Lync, Topology Builder, Edge pool topology, Audio/Video Edge Service

Comments (2)
  1. Teo says:

    Hi Jazzy,

    Great post – I always love hearing more about this topic.  The two statements below sound and STUN, TURN, and ICE all do data transfer.  Do you mind expanding on how the data transfer happens with each?

    " Traversal Using Relay NAT (TURN) and Session Traversal Utilities for NAT (STUN) are protocols that are used for audio, video, and desktop sharing data transfer…"

    "Internet Connectivity Establishment (ICE) is used to traverse NATs and firewalls with audio, video, and desktop sharing data."

  2. rodrigo says:

    Is there any tool to check ports and firewall config for external users over NAT?

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