Lync phone to Exchange UM Traffic Flow


  • We're trying to figure out where to place our Exchange UM servers in our WAN.  When a phone calls voicemail it looks like the traffic is coming from the Pool Server to the Exchange UM Server?  Once the call is setup does the pool server drop off and the phone talks directly to Exchange UM?  Also is it RTAudio and is CAC throttling this?

    This is for an internal phone call.



    1. března 2012 18:45


  • Hello Jobe,

    From the decription: Your UM server is across the WAN in the HQ

    When a Lync client homed on SBA/SBS calls any user and the user is unavailable and enabled for UM, the EXUMrouting component on the SBA will try to route the invite to the UM server associated with the user's dial plan. The SIP signalling will be from the SBA to the Exchange UM. The media flow will be from Lync endpoint to the Exchange UM server.

    If you have UM server across the WAN and the WAN goes down then you can configure voice mail reroute so that the calls to UM can be re routed through PSTN.

    You can refer to and 

    THe codec used is RTAudio and Exchange UM calls are not affected by CAC, CAC only works for Lync endpoints and servers

    • Označen jako odpověď Jobe.Gates 7. března 2012 13:09
    7. března 2012 9:19
  • Hello Jobe,

    Since CAC wont apply to calls made to Exchange UM, you can calculate BW usage for worst case scenario.

    Say for e.g. the branch site has 100 users and the maximum calls the user can make is 100--say 100 calls to 100 users and all the recipient of the call are busy or not available so all the calls will be routed to voice mail and since we use RTAudio and say use 50 kbps per call so for 100 calls we would use 5 mb of traffic across the WAN link.

    Now such a scenario will be rare.. Hope this helps!

    • Označen jako odpověď Jobe.Gates 8. března 2012 20:46
    8. března 2012 11:22

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