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QoS Service Types

Communications Server 2007

The Office Communications Server 2007 media sub-system in Office Communication Server 2007 uses the following two ServiceType values.

The SERVICETYPE_GUARANTEED setting guarantees that IP datagrams will arrive within the guaranteed delivery time and will not be discarded due to queue overflows, provided the flow's traffic stays within its specified traffic parameters. This service is intended for applications that need a firm guarantee that a datagram will arrive no later than a certain time after it was transmitted by its source.

The Real Time Media Communications stack marks the RTP/SRTP Audio packets (default payload type value equal to 0, 3, 4, 8, 101, 111, 112, 114, 115, or 116) as SERVICETYPE_GUARANTEED. This marking is off by default.

To turn it on this marking on, the following is required on all server and client computers:

  • The Windows QoS Packet Scheduler service must be running on each computer.
  • The following registry key must be set to must be set to 1 (DWORD). The marking translates to setting the value of the TOS Precedence field in the header of the IP packets conveying digital speech to 101 (in binary). These marking can be modifying DSCP values for conforming packets in Group Policy snap-in (gpedit.msc). For more information, see the Introduction to Microsoft Office Communications Server 2007 Technical Reference.
    HKEY_LOCAL_MACHINE \Software\Microsoft\RTC\Transport\QoSEnabled
    Bb870407.Caution(en-us,office.12).gifCaution:
    Incorrectly editing the registry may severely damage your system. Before making changes to the registry, you should back up any valued data on the computer.

The SERVICETYPE_CONTROLLEDLOAD setting provides an end-to-end QOS that closely approximates transmission quality provided by best-effort service, as expected under unloaded conditions from the associated network components along the data path.

Applications that use SERVICETYPE_CONTROLLEDLOAD may therefore assume the following:

  • The network will deliver a very high percentage of transmitted packets to its intended receivers. In other words, packet loss will closely approximate the basic packet error rate of the transmission medium.
  • Transmission delay for a very high percentage of the delivered packets will not greatly exceed the minimum transit delay experienced by any successfully delivered packet.

The Real Time Media Communications stack marks the RTP/SRTP Video packets (default payload type value equal to 34 or 121) as SERVICETYPE_CONTROLLEDLOAD. This marking is off by default.

To turn it on this marking on, the following is required on all server and client computers:

  • The Windows QoS Packet Scheduler service must be running on each computer.
  • The following registry key must be set to must be set to 1 (DWORD). This marking will translate to setting the value of TOS Precedence field in the header of the IP packets conveying digital video to 011 (in binary). These markings can be modifying DSCP values for conforming packets in Group Policy snap-in (gpedit.msc). For more information, see the Introduction to Microsoft Office Communications Server 2007 Technical Reference
    HKEY_LOCAL_MACHINELM\Software\Microsoft\RTC\Transport\QoSEnabled
    Bb870407.Caution(en-us,office.12).gifCaution:
    Incorrectly editing the registry may severely damage your system. Before making changes to the registry, you should back up any valued data on the computer.

The two IP packet marking described previously can be disabled by setting the registry key HKLM\Software\Microsoft\RTC\Transport\QoSEnabled to 0. This value means that no marking will be done on any of the RTP/SRTP traffic coming from Office Communicator Server 2007.

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