At the HP analyst convention I wandered round the various technology showpieces that HP had on display and ran into a “unified communications” demo. I’ve discussed unified communications before, pointing out the schizophrenic nature of the market. HP’s demo pretty much illustrated the point, as it married Microsoft’s messaging software with Cisco’s IP telephony, showing that it could pass presence information from one to the other. Incidentally, HP has no particular technology to add to this, other than the various servers required and its experience in implementing such systems.

The fact that HP cared to include such a demo which emphasized the passing of presence information is a sign of the times. After I posted What is Presence and Why Should I Care?, I was contacted by Avaya, so they could brief me on the release of a number of products under their one-X brand. Avaya one-X Communicator is the brand name of Avaya’s Unified Communications offering and they have packaged it for Small Businesses, Teleworkers, Mobile workers and Home Agents. But in truth Avaya were more anxious to tell me about their Presence Server because I’d been writing about presence.

What is a Presence Server?

Put simply, a presence server is a software platform that gathers presence information from multiple providers and then shares it between those providers and any other applications that are interested in it – and it does it all in real-time. The diagram below illustrates Avaya’s Presence Server (I redrew this diagram, because Avaya’s was too wide for this page).

To understand how it works, first consider the collectors/publishers at the bottom. These are pre-built interfaces to proprietary communications applications like Microsoft Exchange and Lotus Domino, standard interfaces to other comms apps (i.e. XMPP. SIP/simple and Web Services) and real-time interfaces to communications devices (AES or SIP).

These interfaces collect and publish presence information in a publish/subscribe way. They are permanently processing presence information and feeding it to the Presence Manager.

The Presence Server is like a Domain Name System, except for people rather than web pages.

It is important to understand this, if you want to understand why a Presence Server is not just useful, but will become a necessity. When you put a url into a web browser it routes you to a web page. But when you make a phone call or send an instant message, it only takes you to a device (a phone or a PC or whatever). It doesn’t necessarily reach the destination (the person) you want to reach. The Presence Server seeks to know as much as it can about presence to improve your chances of getting to the person.

The heart of the Presence Server is the Presence Manager which manages the flow of presence information maintaining the most up-to-date status on presence. In order to do this is consults the Availability Rules Manager which holds a set of logical rules that allows the Presence Manager to estimate “presence”.

The fact to understand here is that the system will rarely be completely sure about the presence of any individual. It can only know about device usage. For example it can know that you have messaging software open on a PC, but it doesn’t know for sure that you are at the PC or even in the room unless you have just sent a message. It may know that you carry a mobile phone, but it may not know that you have it turned on or whether you are able to get a signal. When the Presence Server sends out presence information, it is making a judgement based on the information it has by applying Availability Rules.

Two additional aspects of the Presence Server are that it synchronizes its information about users, devices and policies with other sources within the corporate network and that it provides an API so that it can be called from business applications – as you would probably have guessed.

Why Do I Need One?

The simple fact is that if you have a real-time idea about presence, then you increase the effectiveness of communications and you reduce the latency (the wait time) of many interactions. Everything works better. My expectation is that, in time, presence servers will be as much a part of corporate computing as, well, email servers.

It will take time though.

This is a posting in the Telephony/Communications Integration series of Focus postings.