Computer telephony meets mainstream 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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