Unified Communications relies on open standards to deliver its promise of simplifying communications, improving productivity, and bringing the information worker closer to the frontline of the enterprise.  No better enabler of UC’s promise can be found than with the integration of Avaya Communication Manager with Microsoft Office Communications Server. 

Avaya Communication Manager is the flagship IP PBX that handles enterprise IP telephony and contact center routing.  Office Communications Server is Microsoft’s collaboration suite, enabling Instant Messaging, presence, web, video, audio conferencing, and voice calling.  For enterprises that want the best of both worlds, these two platforms can be integrated via open standards.

Avaya and Microsoft have partnered to develop a tight integration between an existing Avaya Communication Manager environment and a new OCS environment.  It allows Microsoft Office Communicator clients to ‘click to communicate’ and otherwise control calls on their Avaya desk phone, seamlessly, from their PC desktop.  It also provides advanced presence, displaying the phone’s on-hook/off-hook status on OCS users’ buddy lists.  This integration really delivers the sizzle of UC. 

This article outlines the elegant way in which OCS can integrate to Avaya Communication Manager, describes the user experience, shows a reference architecture, and outlines the benefits.

Realizing the Promise of UC

The true promise of UC can be delivered with what Microsoft calls “Remote Call Control.”  Here, users of the Communicator client can invoke communications and control the physical Avaya phone on their desk from their PC.  While this has been done for years with TAPI and other CTI applications, the added value is that now a user’s presence status includes information about whether or not they’re on the phone.  This should eliminate (or at least drastically reduce) the need to start Instant Messages by saying “can i call you?”  If your buddy’s status is ‘In a Call,’ you can save the keystrokes and get right onto the message (“I just won the contract” or “call me ASAP when you’re done.”) 

The main productivity improvement of the advanced UC integration is advanced presence.  Advanced presence takes information from not only the PC and keyboard, but also from the users’ on-hook/off-hook phone status.  Without advanced presence, isolated IM and telephony tools can actually do more harm than good, and more disrupting than unifying.  With the advanced integration, “can I call you” need no longer be answered with, “no I’m on the phone.” 

In this case, the Communication Manager and OCS environments are tightly linked with an intermediary gateway, Avaya’s Application Enablement Server (AES).  AES is the development platform and open-standards way for third-party applications, like OCS, to take control of Communication Manager phones. 

OCS call control is based on an Ecma  technical report, TR/87 (also known as CSTA  over SIP). CSTA standardizes a set of application services to observe and control voice and non-voice media calls.  OCS creates call control messages using CSTA, and then embeds them within SIP payloads.  Conveniently, AES has the capability to understand CSTA, along with other telephony integration standards. 

When a user clicks-to-call from MOC, AES receives the CSTA message and translates it into something Communication Manager (which has no native CSTA code), can understand.  The Avaya phone’s speakerphone on their desktop goes active and ringtone is heard as Avaya Communication Manager makes the outbound call.
 
How does this call flow specifically work?  Here’s an example of a simple inbound call destined for an OCS user with an Avaya phone at their desk.

1. Call comes into Communication Manager from an outside trunk
2. Avaya Communication Manager sends signaling information to AES over the IP network
3. AES sends signaling information to OCS Front-end Server
4. Call simultaneously rings Communicator and Avaya phone
5. If user clicks ‘Answer Call’ on Communicator, Avaya speakerphone or headset goes off-hook.  If call is picked up on Avaya phone, ‘conversation’ begins on Communicator
6. Call can be transferred, put on hold, etc. from either Communicator or Avaya phone
7. Media stream is always between Avaya Gxx0 Gateway and Avaya phone
8. Call can be terminated from either phone or Communicator
9. If there were no answer, Call is forwarded to the coverage path for Voicemail
It is most amazing to see this interaction in person, but using Avaya IP Softphone’s ‘picture of phone’ tool, it is possible to picture what happens.  The activity is depicted in Figure 2 below.  When a call is in progress, you can see that the red call appearance lamp lights up on the Avaya phone, and the Communicator client status button appears red, for “In a Call.”  The counters appear and begin to count up.  Both devices’ call control icons become active. 

Figure 1: Avaya Phone goes off hook when Communicator makes a call.

This advanced integration offers more than just click-to-call and advanced presence.  Office Communicator’s phone icons can be used to control many features of the Avaya phone.  Click hold, and the Avaya Communication Manager puts the call on hold and lights the hold lamp on the Avaya phone.  Click transfer on Communicator and type in a new number or contact, and the Avaya phone transfers the call.  Note that due to the way OCS starts its own multi-party audio-conferences, it is not possible to use Communicator to create three-way conferences on the Avaya phone.  Conference calls have to be invoked from the Avaya phone itself.

The only data passed between the Microsoft and Avaya cloud is signaling; the front-end server (OCS’s SIP registrar) communicates to the AES, which converts TR87/SIP (CSTA) into the call control language that Avaya Communication Manager can understand. Voice traffic is all between Avaya endpoints and their affiliated media interfaces in the Avaya gateway. 

AES 4.1 is required for OCS click-to-call integration, and AES 4.1 requires Avaya Communication Manager 3.0.  AES requires the Unified Desktop license, for which the price is based on Avaya’s nine-tier model.  While more expensive to implement, this integration gives users the ‘as advertised’ functionality of enterprise-class UC.
Summary:

From a market perspective, all parties involved can be happy with such an advanced integration.  IT organizations can provide productivity-enhancing tools to integrate technology that they would otherwise run in silos.  Microsoft and Avaya get to deploy their latest showcase integration and receiving commensurate licensing revenue.  Systems integrators get contracts for what is not a trivial integration.  But most importantly, users can begin experiencing what the UC hype is really all about.