Dial in Conferencing with ShoreTel and Skype for Business 2015/Lync

Hi everyone I haven’t posted anything in a couple of months and have been very busy on a project which I thought I would go over.  Recently the company I work for has been interested in adding dial-in conferencing to our Skype for Business 2015 environment to alleviate some of the costs associated with paying for a web conference service especially since we already were using Skype4B for IM and ShoreTel for our phones.  I already had an Edge server in place for external participants so all I really needed to do was add the dial-in conferencing functionality so that PSTN callers could get in.   Before I get started I’m not attending to give a full tutorial here as many others on the Skype for Business side have written articles but the information is kind of lacking on how to make all these systems talk together and I thought I would provide my notes on what I learned in this experience.  My article is going to be geared at someone using ShoreTel but a lot of this could be applied to anyone with an IP-PBX phone system (Cisco, ShoreTel etc) that wants to hook it to Skype for Business.

This system takes three main parts.  Skype for Business, A VoIP gateway such as the Audiocodes Mediant SBC, and a ShoreTel switch (or whatever has SIP trunks taking PSTN calls back to Skype).


The whole system goes like this,  Skype for Business hosts the calls and conference numbers and the auto attendant for entering your conference ID.  Audiocodes is the interface between the two as they can’t talk to each other directly as Skype uses TLS SIP and ShoreTel uses UDP SIP .  It also does transcoding if needed between different audio codecs (Skype speaks G.711 whereas your phone system may or may not).  Your ShoreTel switch hosts the SIP trunks and takes the PSTN calls from the outside and sends them to Audio codes.

Now I am not going to do a full tutorial from here on out but instead notes of issues I ran into and documentation I have found useful.


  • ShoreTel has provided documentation on how to set this and the AudioCodes box up so that they can talk to each other and talk to Skype for Business. AudioCodes provides similar documentation once you are a registered user on their site after you have purchased support.  https://www.shoretel.com/sites/default/files/SkypeForBusiness_AudioCodes_ST_14_2_AppNote_0.pdf
  • A note to anyone on ShoreTel Connect this document could become irrelevant as I have been told by ShoreTel that Skype can hook to ShoreTel directly without the need for AudioCodes via a plugin for Skype for Business.  I ‘m not exactly sure how it works but I am looking to find out more info from ShoreTel if their engineer ever gets back to me.  If you are on ShoreTel version 14.2 or older or you have a different phone system without Skype for Business support a VOIP gateway from AudioCodes may be your only option.
  • You can install the ShoreTel virtual appliance hosted on VMware instead physical switch.  VMware even has a free bare metal version for free! My finding is this will save you money on SIP trunks as the ShoreTel hardware is kind of expensive just to run SIP trunks and you can add SIP trunks simply by buying licenses from ShoreTel instead of having to purchase more dedicated physical hardware and licenses.  (Hint make sure you buy virtual trunk licenses as there are like three different kinds of ShoreTel SIP trunk licenses).  https://www.drvoip.com/blog/shoretel-support-and-service/shoretel-virtual-trunk-switch-configuration-and-license-impact/
  •  I have encountered ShoreTel virtual switch issues with using G.729 with a virtual switch instead of G.711.  I am not sure if it is some kind of bug in the ShoreTel software but I found some others talking about it in the link below so I simply changed AudioCodes to use G.711 which is probably better as that avoids transcoding.  G.711 does use more bandwidth than G.729 so that is another consideration. https://forums.shoretel.com/viewthread.php?id=906C0000000H5nFIAS
  • Don’t forget to turn on caller id on the ShoreTel side for your sip trunk group unless you like all your callers coming in as anonymous.  Also, Skype4B is supposed to use information in AD to figure out who is who in combination with caller ID also but I haven’t quite figured out how that all works and the documentation is lacking.


  • Avoid transcoding if possible as for example with my 800b ESBC it is limited to 100 sessions with transcoding and 250 without.
  • Make sure you buy the right AudioCodes hardware and licenses as my vendor sold me the wrong one and although I could have added the SBC application license it was cheaper to buy the proper box with the SBC application already installed so be sure it comes with the SBC application license.
  • When Audiocodes needs the ShoreTel IP to send traffic to it is looking for your ShoreTel SIP trunk switch IP not the headquarters server.

Skype for Business


Ok, for now, that is all I can think of and I hope some of this might be useful for someone struggling to figure this out on their own. I will add additional links and content if I find any more.  If anyone has additional questions please post them in the comments and I will try and answer them.



“You need to install additional updates” error message when you try to start Lync 2013

The above error is fairly well documented by Microsoft but thought I would post about it anyway just in case someone comes across the same issue as me.  I had pushed updates out to machines through SCCM and then started getting a handful that Lync/Skype for Business started reporting that Lync had become Skype for Business and that KB3039779 needed to be installed.  Evidently, a few machines we had received a newer update which upgraded them but didn’t have this older update.  Simply pushing out the missing KB3039779 to the machines missing the update resolved the issue.  Update is located here for anyone curious https://www.microsoft.com/en-us/download/details.aspx?id=47056