Topic Last Modified: 2013-11-07

Quality of Service (QoS) is a networking technology used in some organizations to help provide an optimal end-user experience for audio and video communications. QoS is most-commonly used on networks where bandwidth is limited: with a large number of network packets competing for a relatively small amount of available bandwidth, Quality of Service provides a way for administrators to assign higher priorities to packets carrying audio or video data. By giving these packets a higher priority, audio and video communications are likely to complete faster, and with less interruption, than network sessions involving things like file transfers, web browsing, or database backups. That's because network packets used for file transfers or database backups are assigned a "best effort" priority.

Microsoft Lync Server 2013 does not require Quality of Service; if you do not currently use QoS there is no requirement that you install the service before installing Lync Server 2013. If you experience a considerable amount of packet loss on your network the recommended way to alleviate this problem is to add additional bandwidth. If adding more bandwidth is not possible, then you might want to implement Quality of Service instead.

Lync Server 2013 offers full support for Quality of Service: that means that organizations that are already using QoS can easily integrate Lync Server into their existing network infrastructure. In order to do this you must perform the following tasks:

• Enabling QoS for Devices that Are Not Based on Windows. By default, QoS is disabled for computers and other devices (such as iPhones) that run other operating systems. Although you can use Lync Server to enable and disable Quality of Service for devices, you typically cannot use the product to modify the DSCP codes used by these devices.

• Configuring Port Ranges for Your Conferencing, Application, and Mediation Servers. You must reserve a unique set of ports for different packet types, such as audio and video. With Lync Server 2013 you do not enable or disable Quality of Service by, say, setting a property value to True or to False. Instead, you enable Quality of Service by configuring port ranges and then creating and applying Group Policy. If you later decide not to use QoS you can “disable” Quality of Service simply by removing the appropriate Group Policy objects.

• Configuring Port Ranges for Your Edge Servers. Although not required, you can configure your Edge servers to use the same port ranges as your other servers.

• Configuring Port Ranges for Your Microsoft Lync Clients. These port ranges apply only to client computers and are typically not the same as the port ranges configured on your servers.

• Configuring a Quality of Service Policy for Your Conferencing, Application, and Mediation Servers. These policies determine the DSCP codes that are applied to different packet types.

• Configuring a Quality of Service Policy for Your A/V Edge Servers. This should only be done for the internal side of your Edge servers. That's because Quality of Service is designed for use on your internal network and not on the Internet.

• Configuring Quality of Service Policies for Clients Running on Windows 7 or Windows 8. Note that Microsoft Lync Server 2013 does not support QoS for other Windows operating systems, such as Windows Vista or Windows XP.

• Configuring Quality of Service on Microsoft Lync Phone Edition Devices. By default, QoS is enabled for Lync Phone Edition devices. However, you might want to change the default DSCP value in order to ensure that all audio packets in your organization use the same DSCP code.