Bandwidth Management and alternate path

In Microsoft Lync Server you can configure bandwidth management such that media can use an alternate path, if adequate bandwidth is not available in primary path. It is done using the Set-CsNetworkRegion cmdlet and the boolean parameters AudioAlternatePath and VideoAlternatePath. The alternate path is via any deployed A/V Edges and the Internet.


In a topology as the above allowing AudioAlternatePath and VideoAlternatePath would enable Alice and Bob to communicate with media via the Internet in case bandwidth on the direct link between Odense and Copenhagen is unavailable.

Another way of looking at AudioAlternatePath and VideoAlternatePath is as parameters controlling, if media is allowed to flow via the Internet when bandwidth management is enabled. In a scenario as below with Alice being remote on the Internet she will not be able to establish a media session with Bob, if AudioAlternatePath and VideoAlternatePath are not True in the network region incorporating the A/V Edge used by Alice.


My colleague Keith pointed out that I’m not talking about PSTN re-routing in this post. The reason is that alternate path is only related to Internet. I covered PSTN re-routing in this post.

Comments (2)

  1. SachinS2 says:

    Great topic Jen, I have question, if internet on user's PC provided by proxy and external FQDNs are not resolvable when user work from office, how above scenario will work? is there any configuration we can do to make it work? it is great thing if we can get it work.



    Jens: If the Edge Servers are not available when the user works from the office then this feature will not work and PSTN re-routing is the only option.

  2. What if the users switch location temporarely? says:

    Hi Jen, here is another question on this topic.

    What if Bob is on a business trip to Copenhagen and Alice at the same time visits Odense.

    They are not "directly connected" to their Lync Site's Edge server specified for media.. Will the still be able to connect using the Audio Alternate Pathrerouting over Internet from Edge to Edge?

    Tested this in lab?



    Jens>Yes, they would be able to communicate. No, haven't tested it 🙂

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