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Configure Quality of Service (QoS) for Unified Messaging

Topic Last Modified: 2009-10-09

Microsoft Exchange Server 2010 Unified Messaging supports DiffServ through Differentiated Services Code Point (DSCP) marking. In Microsoft Windows Server 2008, TCP/IP performs DiffServ marking when you have installed the Quality of Service (QoS) Packet Scheduler. When you install the Unified Messaging server role on a computer that is running Windows Server 2008 with the QoS Packet Scheduler installed, all outgoing Unified Messaging packets will be marked with a DSCP value that is configured. If you are integrating Exchange Unified Messaging and Microsoft Office Communications Server 2007, Communications Server 2007 also supports QoS by using DiffServ.

Ee633464.note(en-us,EXCHG.140).gifNote:
Layer 3 network devices, such as routers, must also support DiffServ.

When you create a QoS policy on Windows Server 2008, it will be applied to all UDP packets that are set by the Microsoft Speech Worker process (SESWorker.exe). For more information about how to configure Policy-based QoS, see Policy-based Quality of Service (QoS).

Looking for other management tasks related to UM servers? Check out Managing Unified Messaging Servers.

The Unified Messaging server role is installed. For detailed steps, see Install the Exchange 2010 Unified Messaging Server Role.

To perform the following procedures you must log on by using an account that's a member of the local Administrators group on that computer.

  1. Click Start, click Run, type gpedit.msc in the Open dialog box, and then click OK.
  2. In the Group Policy Object Editor window, locate Computer Configuration/Policies/Administrative Templates/Network/QoS Packet Scheduler/DSCP value of conforming packets.
  3. In the result pane, double-click Controlled load service type.
  4. In the Controlled load service type Properties window, click Enable.
  5. In the DSCP value dialog box, verify that the DSCP value of 24 is selected, and then click OK.
  6. In the result pane, double-click Guaranteed service type.
  7. In the Guaranteed service type Properties window, click Enable.
  8. In the DSCP value dialog box, verify that the DSCP value of 40 is selected, and then click OK.
  9. Close the Group Policy Object Editor window.
  10. You can optionally verify that the DSCP values are set correctly by performing these steps:
    Ee633464.Caution(en-us,EXCHG.140).gifCaution:
    Incorrectly editing the registry can cause serious problems that may require you to reinstall your operating system. Problems resulting from editing the registry incorrectly may not be able to be resolved. Before editing the registry, back up any valuable data.
    1. Start Registry Editor (regedit).
    2. Locate the following key: HKLM\Software\Policies\Microsoft\Windows\Psched\DiffservByteMappingConforming
    3. The following default values will be set:
      SERVICETYPE_GUARANTEED (DSCP 40, 0x28)
      SERVICETYPE_CONTROLLEDLOAD (DSCP 24,  0x18)

To perform the following procedures you must log on by using an account that is a member of the local Administrators group on that computer.

  1. Enable the QoS Packet Scheduler service on servers and clients. By default, the QoS Packet Scheduler service is enabled on Windows Vista and Windows XP computers. However, by default, it is not enabled on Windows Server 2003 computers. QoS marking is not enabled by default in Communications Server 2007 because Communications Server 2007 only runs on Windows Server 2003 and QoS marking depends on the QOS Packet Scheduler service running on both server and client computers.
  2. Configure the registry key to enable QoS marking of IP packets sent to and from the Communications Server 2007 server by setting the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\RTC\Transport\QoSEnabled key to 1. Then restart the Communications Server 2007 server to load the QoS settings that are stored in the registry.
  3. Use Group Policy to set DSCP values that mark the IP packets if you need values other than the defaults for Guaranteed service type packets (used for audio) and Controlled load service type packets (used for video). By default, the following settings are applied when you set the QoSEnabled DWORD value:
    • SERVICETYPE_GUARANTEED (DSCP 40, 0x28)
    • SERVICETYPE_CONTROLLEDLOAD (DSCP 24,  0x18)

For more information about QoS and Communications Server 2007, see Voice QoS.

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