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CAC and Media Bypass question RRS feed

  • Question

  • I'm just trying to get my head around CAC and Media Bypass for oou Branch Office sites.  Is this correct:

    Head Office has a Mediant gateway

    Branch Office has a Mediant gateway.

    There is a 2mb link between sites.

    Scenario 1:

    User 1 at Branch Office calls User 2 at Head Office.  CAC checks bandwidth and the pipe is busy. Media bypass allows call to go direct from User A to Branch Office Mediant then via PSTN to Head Office Mediant to User 2.


    Scenario2:

    User at either site calls PSTN number - media bypass allows call to go directly to local site gateway...

    Therefore no mediation server is reqired at the Branch Office?
    Monday, April 30, 2012 7:23 AM

All replies

  • Although both Media Bypass and CAC can be enabled at the same time in your Lync configuration they can not both be applied to the same call at the same time as the features are mutually exclusive.  This means that for each call if Media Bypass is applicable then CAC polices are not used, but this makes sense as Media Bypass is only applicable to calls destined for the PSTN which are not relevant for CAC management.

    Thus in Scenario 1 media bypass is not applicable because that is a peer-to-peer Lync call.  So CAC will be used instead and if deemed appropriate based on available bandwidth Lync may decide to actually route that call over the PSTN.  And Scenario 2 captured the basic functionality of Media Bypass.

    See this section of the TechNet documentation for more details: http://technet.microsoft.com/en-us/library/gg398203.aspx


    Jeff Schertz | Microsoft Solutions Architect - Polycom | Lync MVP

    Monday, April 30, 2012 11:13 AM
  • Hi Jeff, thanks for the reply.  This was my basically understanding but my question now would be when CAC decides to place the call over the PSTN is a Mediation server needed?  I'm trying to get rid of the Mediation servers at the Branch Offices but if CAC decides to place a call over the PSTN and still sends the audio to the Head Office Mediation server for translation this defeats the purpose...

    Tuesday, May 1, 2012 3:06 AM
  • Hi,

    Though you enable media bypass to the branch site, a mediation server is still needed to find the gateway for Lync FE server of branch site when a call want to be route to PSTN.


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    Tuesday, May 1, 2012 5:59 AM
  • Hi Sean - thanks for the reply.  So at what stage does a Branch office not need a Mediation server located on site?  Or does EVERY branch office require an onsite Mediation Server?
    Tuesday, May 1, 2012 8:00 PM