Client Configuration
,QoS tagging of the media is performed by the Lync client itself, so it must be provisioned in a way that it understands what ports to use for each type of traffic. By default, no tagging is done and all traffic uses the port range 1,024–65,535. The Lync client supports using different port ranges for the following types of traffic and recommends a minimum number of ports for each modality. Using port ranges that are below the recommended minimums increases the chance for a media request to fail.
• Audio (20 ports required)
• Video (40 ports required)
• Application sharing (4 ports required)
• File transfer (4 ports required)
First, to enable separate port ranges for each media type, run the following command:
Set-CsConferencingConfiguration –ClientMediaPortRangeEnabled $true
Next, define a unique port range for each type of traffic. As an example, the ports used on the client side can be the same as on the server. The sample numbers used here are well beyond the minimum number of ports required and are used only to show how the default port ranges can be moved. The port ranges used should be limited to the recommended sizes for ease of management and troubleshooting.
Set-CsConferencingConfiguration –ClientAudioPort 49152 –ClientAudioPortRange
8348 –ClientVideoPort 57501 –ClientVideoPortRange 8034 –ClientAppSharingPort
32768 –ClientAppSharingPortRange 16383 –ClientFileTransferPort 24733
–ClientFileTransferPortRange 8034
Creating a QoS Policy
After modifying the Lync clients and servers to use specific port ranges, QoS policies must be created to add the appropriate DSCP value to traffic originating from each port range. The steps required to use policy-based QoS through Group Policy are similar, but the port ranges used for servers and clients will likely differ. Create at least two separate policies: one for servers and one for clients. To create a new policy, perform the following steps:
1. Open a new Group Policy object.
2. Expand Computer Configuration, Windows Settings, and then click Policy-Based QoS.
3. Right-click Policy-Based QoS and select Create new policy.
4. Enter a name for the policy, such as Lync Audio.
5. Enter a DSCP value, such as 46 and click Next.
6. To limit the tagging only to Lync clients, select Only applications with this executable name and enter communicator.exe. Click Next.
7. Allow the policy to apply to any source IP address and any destination IP address.
8. In the Select the protocol this QoS policy applies to, select TCP and UDP.
9. In the Specify the source port number section, select From this source port number or range and enter the range used for audio traffic, such as 49152:57500.
10. Click Finish to complete the policy.
Repeat these steps for each type of media using a unique port range, which should be tagged differently. Figure 15.4 demonstrates what a policy with separate audio and video settings looks like.
Note
The A/V Edge service behaves a bit differently. First, because it typically is not part of the domain, it might be necessary to create the policies locally on each server. Second, the port range used to define each service should be specified as a destination port instead of source port. This ensures traffic, which the Edge server uses to communicate to a Front End pool, is marked correctly.
Windows XP QoS
Because QoS policies can be created only on Windows Vista or later operating systems, the process for enabling QoS on Windows XP is slightly different. Windows XP QoS marking is also not as flexible as policy-based QoS and can only mark audio traffic as SERVICETYPE_GUARANTEED and video as SERVICETYPE_CONTROLLEDLOAD.
First, verify the QoS packet scheduler is installed on the client. Secondly, run the following command on a Lync server:
Set-CsMediaConfiguration –EnableQoS $true
Before the Lync client attempts to tag packets, the DSCP values should be modified using Group Policy.
1. Open a new Group Policy object.
2. Expand Computer Configuration, Administrative Templates, Network, QoS Packet Scheduler, and click DSCP value of conforming packets.
3. Double-click Guaranteed service type.
4. Select Enabled and enter a DSCP value such as 46.
Repeat these steps for the Controlled load service type to tag video media.
Lync Phone Edition QoS
The final client type that can use QoS settings is the Lync Phone Edition client, which can run on third-party partner hardware. Lync Phone Edition settings are determined through in-band signaling to the devices. In addition to a DSCP value for audio traffic, the Lync Phone Edition clients also support 802.1p. To set the Lync Phone Edition QoS settings, use the following command on a Lync server:
Set-CsUcPhoneConfiguration –VoiceDiffServTag 46 –Voice8021p 5