Architecture of an Enterprise-Capable Fax Server

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An "Enterprise-Capable" fax server must address a variety of applications and computing environments. The many configuration possibilities and the need for reliable operation, ease of installation and ease of use, dictate the need for a solid yet flexible architecture. This white paper illustrates the relationship between components and describes the most important aspects of product architecture. Through this paper, we intend to provide prospective customers with a good understanding of the elements of a fax server that should influence the purchase decision. We hope you will agree that Faxgate represents an excellent choice.

GartnerGroup recently published a research note entitled "Fax Servers: What's at the Core?," authored by Mark Gilbert and David McCoy. Esker has a limited quantity of licensed reprints from GartnerGroup for selected distribution with this paper because we believe the Faxgate architecture compares very favorably with the GartnerGroup's view. However, this paper does not require supplemental materials of any kind to fully understand the content.

Important Disclaimer The views expressed in this paper are the sole views of Esker, SA, and its subsidiaries, and in no way represent the views or opinions of the GartnerGroup, nor should they be construed as an endorsement by any third party.

Architecture Overview

The following diagram illustrates the Faxgate architecture.


Essential Functions

Any fax server architecture must provide the following essential functions:

  1. Format Conversion

  2. Telecommunications & Data Network Connectivity

  3. Client & Viewing Capability

Without these functions, a fax server could not perform even the most basic fax automation task.

Format Conversion - Rendering Engine & Forms Merge

Rendering. In the early days, a fax resulted exclusively from scanning a physical document and generating a standard image file for transmission. Today, computer-generated documents originate in many formats, none of them suitable for direct submission as a fax. These formats include:

  • Desktop application files generated by word processing and spreadsheet applications.

  • Simple text-based print files commonly found on mainframes and UNIX systems generated by multi-user front and back office applications.

  • Print oriented file formats including the commonly used Postscript and PCL and high-volume, production-oriented schemes including AFP from IBM and Metacode from Xerox.

  • Image files including GIF, JPEG, BMP and more.

Ultimately, all faxes end up as G3 (tif) images. Fax has become pervasive, in part, because international fax standards have eliminated the incompatibilities of various computing platforms. Anyone with a fax machine anywhere in the world can communicate with any other fax machine regardless of the content of the document.

While all fax servers on the market offer some type of conversion, the method and breadth of conversion functionality differs significantly. Enterprise-capable fax servers should offer multiple conversion techniques to meet the widest possible range of source file requirements. These include:

  • Conversion of any Windows-based application by launching the application on the server and performing a shell print.

  • Postscript and PCL print files.

  • Advanced Function Presentation (AFP from IBM) and Metacode (from Xerox), both designed for extremely high-volume production printing.

  • ASCII or EBCDIC text file conversion. Mainframe- and UNIX-based applications typically generate print files in this format.

Forms Merge. The last item in the list above, plain text print files, often generate the largest single application volume in a company. However, they do not result in a fax that has the look and feel of a well-designed document. Generating documents from simple text files that represent your business properly requires the ability to merge the print file with an electronic form. The approach should minimize the need for application changes by using an external template to define the formatting of the fax. The external template file "maps" lines in the print output to areas on the electronic form, specifying font, orientation, logos, signature files and the like. This way, a format change does not require changes to the business application.

Telecommunications & Data Network Connectivity

Telco Interface. The telecommunications interface provides connection to the public switched network. This interface comes from third party developers of specialized hardware ranging from low cost, consumer-oriented fax-capable modems to industrialized, high-performance (and high density) fax boards. Good examples of high-performance fax boards come from Brooktrout and Dialogic/Gammalink.

The lowest common denominator offered by all such products supports a single analog telephone line with the basic signaling (for example, duel tone multiple frequency, or DTMF) to initiate the call. For higher volume applications, digital interfaces offer more capacity and better reliability. In Europe, primary rate ISDN (2 megabits/second, 30 fax channels) and basic rate ISDN service predominates. In North America, the primary digital standard is T1 (1.544 megabits/second, 24 fax channels). Enterprise-capable fax servers should support fax boards from the leading manufacturers that address the international analog and digital standards because of the significant cost savings in high-volume applications.

Network Interface. Basic network connectivity must include both Ethernet and Token Ring LAN at the physical layer. Specialized physical connections should also include IBM 3270 (coax) and 5250 (twinaxial). At the higher levels, an enterprise-capable fax server should support connection to the leading LAN servers such as Novell NetWare and Windows NT Server, and run legacy protocols such as Systems Network Architecture (SNA) in both traditional LU mode and APPC.

The server should also offer value-added services in a TCP/IP environment, such as the ability to use lpr/lpd and lpq to send and check the status of fax jobs. This should also include the ability to automatically send activity logs for programmatic checking of high-volume workloads. This eliminates the need to manually search and handle faxes that do not reach their destination (due to conditions such as wrong numbers, out of paper at the receiving end, etc.).

Client & Viewing Capability

Enterprise fax servers should offer the ability to send, receive, and view a fax efficiently. The client interface should minimally offer the following features:

  • Support for both 16- and 32-bit versions of Windows.

  • A Web browser alternative for non-Windows platforms.

  • Real-time or near real-time status of fax jobs in process submitted by a user.

  • Image viewing, storing and resubmission.

  • Creation of a cover page.

  • Multiple language support.

Without question, fax servers must provide client and viewing functionality to have any value. However, we believe that client and viewing technology should lie outside the core architecture of the system. Rather, access to the files for viewing and manipulation should come through a server-based API. This approach improves the stability of the server software, and provides the flexibility to integrate best-of-breed client technology. Hence, we depict the presence of the Client API as part of the Faxgate server architecture, and the client technology (including the viewer) as existing outside the server, but tightly integrated through a true client/server API.

Differentiated Functions

The essential functions described above must exist and run reliably for any fax server to function. However, today's computing environment demands far more than these three basic functions. Choosing the right solution requires you to examine functions that differentiate the available alternatives. The leading solutions all offer these functions in some fashion. It is the extent to which they go and the way in which they implement that provides the basis for selecting the best solution.

Elements of a fax server architecture that further differentiate alternatives include:

  1. Application Program Interfaces

  2. Integration with GroupWare & Messaging

  3. Notification & Advanced Inbound Routing

  4. Scheduling & Least Cost Routing/Load Balancing

  5. Administration, Security & Accounting

Application Program Interfaces

Although desktop faxing represents the most visible and easy-to-implement application for fax automation, the highest financial return comes from integration with business applications. To operate successfully, companies must generate many documents, including:

  • sales proposals

  • invoices

  • quotes

  • trade confirmations

  • price lists

  • reports

  • purchase orders, and many others

These critical documents often come from multi-user transaction-oriented systems running on mainframe, mid-range or shared LAN-based platforms. Automating the transmission of these documents saves substantial time and costs, and often provides a competitive advantage when speed of delivery differentiates a service or business relationship.

Programmatic interfaces should exist in several respects.

  1. Windows-based API. Interfaces such as DDE or COM provide the software developer a way to directly submit work to the fax server without forcing the user to change the way they interact with the business application. This type of API should run on the client since the function supporting the user interface runs there.

  2. Production API. This type of API supports integration with ERP applications from vendors such as SAP and BAAN, and allows the integration with other off-the-shelf and custom developed applications. This type of API should minimize the programming effort to integrate production applications. It should employ standards and vendor-certified interfaces to the extent possible, and use stable, widely-installed protocols such as TCP/IP and SNA.

Integration with Groupware & Messaging

Major computing environments today include Windows-based applications both for personal and group productivity. The emergence of messaging-oriented GroupWare has made it highly convenient to include fax communications with e-mail and the web. An enterprise fax server should send and receive fax documents from the major GroupWare products, including Microsoft Exchange and Lotus Notes. This integration should employ the standard techniques endorsed by the vendors (e.g. Exchange Connector) and seamlessly integrate into the directory and management structure of the GroupWare.

Notification & Advanced Inbound Routing

Notification. Due to the time critical nature of faxed business documents, the sending party requires status information. Consider the following situations:

  • The receiving fax machine has no paper

  • The fax server encounters a constant busy signal and fails all retries

  • An incorrect phone number dials a voice line

Each of these situations requires corrective action. Notification insures that someone has the opportunity to correct the situation preventing the fax from successful transmission. Notification should be available through e-mail/GroupWare, the client, the server's administrative interface and automatically through upload of activity logs or individual job reports for programmatic handling in high-volume applications.

Advanced Inbound Routing. Most commercially-available fax servers have the ability to route an incoming fax to a destination. In addition to manual routing through e-mail or client technology, this feature normally uses either the line on which the call arrived or the extension as the criteria for routing. This type of simple routing scheme works well when you require a one-to-one correspondence between individuals the sender and receiver.

Intelligent routing refers to the ability to make routing decisions on more sophisticated criteria. This could include a combination of the dialed number and the day of the week, the time of day, the size of the file, the date, or any other attribute of the fax. The ability to intelligently route an incoming fax document provides significant value in applications that require relatively complex decisions.

For example, call and processing centers often deal with high volumes of time-critical documents processed by groups of analysts or customer service specialists. These groups often have responsibility for a geographic region or a time zone. They may also work in shifts and different locations. Routing an incoming loan application (for example) to the correct work group requires the server to know more than just the line on which the call arrived. The application will be routed based on the originating phone number and time of day (as an example).

Scheduling & Least Cost Routing/Load Balancing

Scheduling. Scheduling, or queue management, must take into account and the priority of any particular job waiting for processing. The system should offer at least three levels of priority, urgent (for extremely critical, high priority documents), normal, and low (for non-time critical jobs). In addition, the system should offer the ability to schedule a job for later sending to take advantage of lower rates (e.g. night or weekend).

The scheduling function must also address the need to keep the available lines fully utilized. An enterprise-capable server often has multiple lines (up to 30 or more), the fax hardware usually represents the single highest cost component.

Least Cost Routing/Load Balancing. Enterprise-capable fax servers should support efficient operation in geographically-dispersed locations and high-volume applications. Least-cost routing permits the administrator to assign a cost that the servers use to determine which server should launch the telephone call. The basis for the cost is the tariff or rate charged by the service provider (PTT or long distance company). This way, a document originating in New York, destined for a fax machine in Paris, could be sent over the telephone network by a server in Frankfurt.

Load balancing differs from least-cost routing in the basis for assigning cost. Load balancing provides the ability to determine the size of the work queues in a collection of servers and assign the work to the server that can send the fax the soonest. Therefore, cost is proportional to the amount of work in the queue.

Administration, Security & Accounting

Administration. Enterprise-capable fax servers should offer convenience and control in the administrative and management interfaces. This interface must provide real time status, the ability to manipulate servers anywhere in the network from a central location, and historical reporting. It should take advantage of widely adopted or standard interfaces and techniques and minimize the use of proprietary means.

As one example, Microsoft recently developed a tool for managing and administering Windows NT networks referred to as the "Microsoft Management Console" or MMC. MMC centralizes the management and administration of both the Windows NT servers and compliant applications that run in that environment. MMC provides an ISV-extensible framework that provides a familiar Explorer-like MDI (Multi-Document Interface) user interface to the network administrator. Faxgate takes advantage of the MMC capability of Windows NT Server to provide leading edge, highly integrated management and administration of networked fax servers.

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Fax servers in this category should protect against unauthorized access to incoming fax documents, administrative functions, and the telecommunications facilities of the server. In a desktop environment, they should take advantage of the standard security mechanisms of the leading LAN NOS products like Windows NT Server to accomplish these objectives.


Accounting functions should allow the administrator to report by individual, department or division (according to an accounting code) the resources used. Activity logging should capture number of pages (per fax and total), total transmission time and number of attempts. The system should support widely-accepted reporting packages such as Crystal Reports to allow the customer to choose their preferred reporting package. However, the product should also include standard reports that provide basic, useful information in measuring system activity, and measuring and allocating costs associated with the service.


Enterprise class fax servers provide essential functions and capabilities that differentiate them from products designed for homogeneous environments and convenience-oriented applications. They must support many sources of documents, provide reliable operation at high volumes, integrate with messaging solutions and applications, allow cost-optimized deployment, and provide a convenient way to manage and account for the operation of the system. Faxgate meets these criteria and more.

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