QoS - DSCP marking for Mediation Server / Front End Servers / Exchange UM RRS feed

  • Question

  • I'm trying to get QoS marking to work with my Mediation Server, Unified Messaging Servers and my Front End servers.


    From the TechReference for OCS guide:

    In order to enable QoS marking in your Office Communications Server environment, you will need to do the following:

    ·         Enable the Windows QoS Packet Scheduler service on servers and clients

    ·         Configure the registry key to enable QoS marking of IP packets sent to and from Office Communications Server

    ·         Use Group Policy to set Differentiated Services Code Point (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 (used for video)

    To enable packet marking by the Real Time Media Communications stack to guarantee that IP datagrams for audio and video will arrive within the guaranteed delivery time, set the value of the following registry key to (DWORD) 1 on both server and client computers in your environment:



    This is the same procedure on the Exchange UM servers apparently...

    Even after rebooting the servers (per instructions), I cannot get the DSCP settings to be marked for outgoing packets.

    On my Vista client -  once the Group Policy was set - I could see the packets marked.  But not without a policy set.

    I was assuming there may be a “trick” to get this to work, but I have not seen it yet.   I don’t see the same policies (nor should there be) for XP or Windows 2003 servers.  And the QoSEnabled = 1 option seems to have no effect on outgoing packets.  


    Any ideas?




    Steve Hahn
    Friday, January 30, 2009 3:41 PM

All replies

  • Hi Steven,

    Dont forget to set the correct DSCP marking in OCS at the pool level, or in the case of a standard edition this is on the front end service. Ensure that your network is also set to  trust the DSCP markings coming from your servers. Depending on your network equipement unless this is set your DSCP markings may be stripped. I have confirmed on our mediation server the setup you describe is indeed correct and does work. The defualt setting for OCS for marking voice traffic is DSCP 40. Depending onyour network setup most network vendors recommend 46 for expedited forwarding.

    Chris http://voipnorm.blogspot.com/
    Saturday, January 31, 2009 7:48 PM
  • Thanks for the reply....

    Verfied everything I could think of:

    • I've taken network traces locally on the servers, and do not see the markings from the Front Ends or Mediation Server on outboudn traffic.
    • I DO see incoming traffice from the PBX marked
    • It is an Enterprise Pool -  under Front Ends / Properties / Voice Tab / Advanced Options - Configure,  and it is set to "40".   I've mot familir with the "pool" settings.
    • Verified that HKLM/SOFTWARE/Microsoft/RTC/transport  is where the QoSEnabled setting is set
    • Verified that the QoS Packet Scheduler is associated with the network Adaptor

    Rebooted the server just to be sure, retook traces - same results.

    Checked event logs, nothing listed - not sure where else to look.

    Maybe R2 will solve the problem.  :)

    - Steve

    Steve Hahn
    Monday, February 2, 2009 4:55 PM
  • Just a note, using wireshark packet analyzer you can check the incoming packet markings of your PBX and match those packet markings, or changing your QoS to 46 isnt going to hurt for a quick test. Unless you are conferencing you are more than likely not going to see RTP streaming from the front end servers. Packet scheduler should be enabled in the properties of the network interface you want QoS to work. Its pretty easy to setup and very hard to screw up.

    Chris http://voipnorm.blogspot.com/
    Tuesday, February 3, 2009 3:28 PM
  • Using Netmon 3.2, which identifies the packet type (RTP) and what application sent the packet.   I am monitoring from the Mediation server, so that I can see the traffic go through.  (Hence, can see the RTP going both ways)

    QoS packet scheduler is running on all interfaces on the Mediation server as well.    (Either from the PBX or to the next hop, it seems to be not marking traffic on its way out)

    I'll post to the thread if I find an answer.



    - Steve

    Steve Hahn
    Tuesday, February 3, 2009 3:34 PM