I had been chasing down this issue for some time now and finally got to the bottom of it. The symptoms were when a PSTN call comes into Lync and when the Lync user answers the call, the lync client (or vvx phone) would just sit there stating “connecting….connecting…” and the call would never connect.
Just as fast as the problem showed up it would go away. I started putting some pieces together in that it had to do with the number of Lync clients logged into. The next step was to get some syslogs from the SBC when i could get the problem to reproduce. From these logs i started seeing the below:
Notice how it says “there are 4 entries !!!” this was the number of lync clients i was logged into. You can use the get-csconnections.ps1 tool to find how many clients you’re logged into (Google/Bing for it if you don’t have it….it’s a great tool). So when i was logged into 4 clients and i attempted to use my cell phone to call my lync number i would get that “connecting….connecting..”. The moment i logged off one of those lync clients and made another call from the PSTN into lync, BOOM the calls worked just fine. Log back into that 4 client and “connecting….connecting…” would happen again.
So i thought i had figured it out…there’s something about being logged into 4 clients that the SBC didn’t like. Being the proud IT guy I am, i go to my branch chief and wanted to show him what I had uncovered. Before going into his office i used the get-csconnections.ps1 tool and saw he was logged into 6 devices. I was sure if i called his lync number from my cell phone it would fail. Nope, worked like a charm.
So I got on the phone with AudioCodes and they confirmed we uncovered a new bug in all MK4 Firmware version that only supported 3 MEDIA BYPASS clients. We had Media Bypass turned on. The key word here was MEDIA BYPASS clients. I ran the get-csconnections.ps1 tool against my branch chiefs account and sure enough he was logged into 2 devices that leveraged media bypass (a cx series phone and a lync client). The rest of his connections were from his multiple iPhone/iPad…which hook in through edge and can’t used Media Bypass.
So there you have it, all Firmware versions of MK4’s can only support 3 clients that can leverage Media Bypass. AudioCOdes is working on fixing this and i’m told the new Firmware will allow up to 24 “Forked” entries. It was an over-site by their development team as the MK1 support 24 “Forked” entries. Until the Firmware is updated, we have disabled Media Bypass and all is better. Clients can be logged into more than 4 Media Bypass clients and receive calls without issue.
Update: This bug is fixed in 6.8A.244.006. This version now support up to 20 Forked objects (thus 20 media bypass clients logged in under the same user)