Understanding UCMA Back to Back Calls Part I

The BackToBack call class is the deep end of the UCMA feature pool in this developers opinion.  There are many examples out there in the programming world, but only a handful are useful.  Over the next several weeks it is my goal to explain this class in a manor that any skill level of developer can understand and benefit from.

So where do we begin?  How about we start with what in the heck is a back to back call?  There are a lot of different ways to answer this question but here is the one that turned on the light bulb for me.

B2B calls are a tool that gives you NSA like control over your local Lync/Skype4B server's calls.  B2B calls can be used for things like this;

1.  Silent Monitoring - Allowing a supervisor to listen to a call between a outside caller and local agent.

2.  Call Recording - Allowing every call coming in or going out of the system to be recorded.

3.  Whisper Coaching - Allow a hidden call participant to coach new agents when they deal with customers for the first time.

These are just a few examples.  The most powerful thing for me is the ability to combine these with conferences to come up with advanced solutions that rival and exceed what is available on any traditional pbx system.

So how does it work?  Think about it this way, if 2 people are on a call the only way for me to be able to hear the conversation is to stick my ear to the door (hear 1 side), or capture all the network packets and try to reconstruct the call.  Neither of these is a good option, and B2B simplifies this whole process.  Using MSPL you can pass every call that comes in to a UCMA endpoint.  That endpoint can see who the call is supposed to be for, then connect the 2 callers, while remaining in the middle of the call.  While in the middle it can have access to the SIP messages, as well as the MCUs and audio.

So what does it look like?  Here is my lonely UCMA application not able to be involved with a call between callers.

Simple illustration of a typical user to user call.

It's pretty sad, he's just sitting there burning CPU cycles completely left out of the conversation.  So what does it look like when he uses a B2B call to get in the middle, unbeknownst to the callers?

Simple illustration of a user to user call, being completed via B2B by UCMA

You see with the B2B call the UCMA application can manage both call legs, without the callers having any idea he's in the middle.  This is the most simple way I can illustrate the idea itself without bombarding you with code examples, and terminology.  Next week I'll showing you some of the basics, and we'll begin working on our call recorder / conference help-desk example.

Doug Routledge, C# Lync, Skype for Business, SQL, Exchange, UC Developer  BridgeOC
Twitter - @droutledge @ndbridge