Mac S4B Client – Major Flaw

Man it’s been a long time since i’ve written a post.  This is one of many i plan to write over the next few days / week.

As I’m sure most of us understand, the Mac Lync 2011 client is junk.  Every time i get a ticket from a Mac user i’m pretty much forced to say “ is what it is”.  This is well known in the Lync/Skype environment.  So when Microsoft started rolling out the beta preview of the S4B Mac client, my organization was extremely interested in getting our hands on it early and giving it a shakedown.  For the most part I’ve gotten great feedback from our beta mac users.  What is little known is there is a MAJOR flaw in the mac client.  Lets discuss..

If you aren’t a member of the SkypePreview i HIGHLY recommend you get an account (  There is a really good video by Jason Collier called SfbMac Signaling and Media.  I tried to find a place where it was posted for all to watch but couldn’t. If someone reading this knows some other place other than on the SkypePreview site, please let me know.  This video outlines how the new Mac client behaves with Signaling and Media flows.

Ok so here’s the rub.  Long story short ALL signaling  from the new S4B mac client is done through the Reverse Proxy.  Thus if you are inside your organization, even to talk to the person next to you, the Mac client will send signaling through the RP.  Once candidate promotion happens, the media should be P2P.  Well this sounds great but what about this.

My environment has two geographically remote locations and to provide WAN survivability we purchased AudioCodes M1K’s with SBA’s inside of them.  Accounts at these location are homed to the SBA.  The reason they are homed there is because if our WAN goes down the Windows Lync/Skype clients and VVX/CX phones will fall into limited functionality mode but can still call 911 or to order pizza.  Now, throw in the new S4B Mac client.  Should one of my users be homed to the SBA and our WAN goes down (thus no access to RP), those end points are literally out of luck.  Those clients will essentially fall off the network and be unable to participate in any Modality including calling 911.  Why…because all signaling is done through the RP.

The good news:  I’m fortunate to have made contacts in the past with Jason Collier and Richard Schwendiman (Jason/Richard…if you read this thanks for guys have been great).  I outlined this issue to them a few weeks ago and i have faith that Microsoft will fix this issue before it becomes GA.  That is, to not have the S4B Mac client be dependent on the RP.


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