Unified Messaging

Unified messaging is a simple concept: All your messages--voice, email, fax, data (such as documents)--go to one inbox. Everything in your inbox is accessible from your desktop PC, any telephone, or your laptop computer. From your desktop or a Web browser anywhere, you can review these messages, which appear as single-line summaries on your inbox screen. Click the message you want, and you see or hear the message, no matter what medium the message is in. Or using any telephone, you can hear your voice messages, forward received faxes to the nearest fax machine, or even have selected email messages faxed or read to you.

Such messaging solutions are readily available today. Recognizing that work is an activity, not a location, unified messaging vendors offer universal access to all your message types.

Unified messaging offers significant benefits. It simplifies communication and saves time. You no longer need to run separate programs from your desktop to get your email, voice mail, and faxes. Using a screen to access your voice mail is more efficient than pressing buttons on your phone to wade though an unseen list of voice messages.

Integrated and Unified Messaging Defined
Unified messaging describes generic universal access to one multimedia mailbox. Integrated messaging refers to an architecturally different implementation of the unified messaging concept. Each technology has benefits and challenges.

Unified messaging systems present messages to users through one interface, but you maintain all message types and user directories in one set of data stores. As shown in Figure 1, although the underlying special interface cards for receiving and sending the fax, voice, and email messages can be in separate server systems, all messages point to the same storage database and use common message storage resources. Also, only one copy of each message exists, no matter what the message type.

Integrated messaging systems present messages to users with one user interface (usually the email client) that displays one virtual inbox that references different message locations, or stores, for each medium. The enabling technologies for this approach are open-messaging standards and their APIs such as Messaging API (MAPI) and Vendor Independent Messaging (VIM).

As Figure 2 shows, independent servers manage email, voice, and fax message types; more important, the underlying server databases are independent. However, this scenario often requires that you maintain a separate copy of the non-email messages on the email server, too. Also, the user directories are separate; you store and maintain each directory on its respective server.

The immediately obvious benefit of unified over integrated messaging is a single point of administration and control for the system. Maintaining one user directory instead of three or more can be a significant administrative advantage in large enterprises.

But deciding which messaging solution is best is not easy. One advantage of integrated messaging over the unified messaging is that you can make disparate legacy message servers appear as one with the appropriate client and accompanying software. This solution can be less costly than a unified messaging solution because corporations that already have fax and email servers don't have to replace them; the corporations can just add a voice mail server and special software to enhance the email client to display voice messages. In this example, the client has to synchronize the different messages, message storage locations, and user directories for each message server.

Basic Architecture
To construct a unified messaging system (as shown in Figure 3), you must assemble several system components, including email, voice, and fax servers and the corporate Public Branch eXchange (PBX) and LAN-connected workstations. The voice server contains the physical interface between the corporate LAN and the internal PBX; the voice server lets telephone callers dial in from outside the company or from their internal extensions (if they have workstations without multimedia capabilities) and create and retrieve voice mail messages. Fax servers contain the necessary fax cards and software for sending and receiving faxes over phone lines.

Phone lines connect to both the voice and fax server platforms (in some cases, one voice and fax server platform) so the servers can handle incoming and outgoing calls. Most often, the PBX lets you access the voice and fax lines as extensions inside the company and by a direct Public Switched Telephone Network (PSTN) for outside calls.

You can access message objects in your unified messaging inbox via a GUI or a telephone user interface (TUI--that is, calling from any push-button telephone). The GUI displays a list of messages on the screen; an icon next to each message depicts the medium. You point and click to access the message you want. The GUI can be Web-based, making message retrieval possible via any intranet or Internet connection.

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