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Designing networks: Tools of the trade

None of the products did everything we wanted, but Compuware's EcoPredictor excelled at using an intuitive interface to tell you how well a proposed design will work.

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Chrysler couldn't have created the Intrepid automobile, Boeing its 777 aircraft nor Intel its Pentium chip without using advanced design software. Chrysler engineers create virtual car parts, assemble them on the computer and then observe the resulting automobile's performance on simulated roads and in a simulated wind tunnel with the help of design tools. For the 777, Boeing uses similar tools to simulate everything down to maintenance and repair of aircraft to understand how aviation technicians will be able to reach into small, narrow places with wrenches. To avoid delivering buggy firmware, a chip maker runs its designs through logic test simulations before etching those designs onto silicon.

When you design an entire network or make significant changes to an existing one, you too need serious design software.

To find out which vendor offers the best network design and planning tool, we invited software companies to submit products for review. Visionael sent us Visionael 6.4, Compuware shipped its EcoPredictor 3.2 and Microsoft forwarded Visio Professional 2002 with Enterprise Network Tools. We also downloaded NetRule 4.0 from Analytical Engines' Web site and we obtained a copy of Bert Houtriet's shareware Didyma 1.72 from his Web site.

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Despite its inability to discover an existing network and slow performance when recalculating the effect of proposed changes to a network, EcoPredictor emerged from our testing as the network design tool of choice.

The visual design environment is intuitive, and its range of drawing tools and supported network components let us clearly express our network changes, albeit not as precisely as Visio Professional 2002 with the Enterprise Network Tools option. EcoPredictor's calculations told us accurately how the proposed changes would affect the network, and the tool's reports did a good job of depicting the nature of those changes.

Looking for perfection

A perfect network design tool should be able to discover a network, offer an intuitive visual design environment for diagramming network changes, crunch numbers to simulate how a new application or new network components will affect response times and produce reports documenting the existing and proposed networks. Unfortunately, none of the tools we reviewed offered all four functions.

NetRule and EcoPredictor have design, simulation and documentation features, but they can't discover an existing network. But both products can import network device information discovered by a third-party product such as Hewlett-Packard's OpenView, Network Associates' Sniffer or Agilent's Advisor.

Visionael is a superior tool for discovering, designing and documenting a network, but it didn't let us simulate application or network activity. Didyma can discover, design and document a network, but it can't simulate the effect of the changes you make. Visio is an excellent network design diagramming tool that, with the Enterprise Network Tools option, can discover and document a network, but it can't simulate application activity within the network.

The network-discovery process for all these products gave us a network planning and design starting point that required considerable manipulation before we could begin creating a representation of the network suitable for diagramming our proposed new network configurations. This manipulation consisted of the consolidation of computers into groups, the identification of various network components and the specification of interrelationships among the network nodes.

We also noted that Layer 2 discovery - which you need to perform to gather port-level network details before beginning a significant design effort - is easier to talk about than accomplish. The problem complicates the job of designing and documenting network extensions.

The difficulty lies not in the discovery software - which typically queries bridge tables, router tables and the proprietary Management Information Bases of devices from Cisco or Nortel to find out what's connected to what - but rather in the accuracy and accessibility of that information.

Virtual LANs, incorrectly maintained or out-of-date tables and unmanaged devices that sit between the discovery software and some outlying branch of the network all conspire to hide or obfuscate network details.

EcoPredictor can directly import data from Compuware's EcoScope - a Layer 3 application-flow product that collects data from distributed probes and centralizes it. Furthermore, EcoPredictor offered the widest choice of topology and traffic import sources of all the products we tested. These include Aprisma (formerly Cabletron Systems) Spectrum; Castle Rock Computing SNMPc; Computer Associates' Unicenter TNG; HP OpenView Network Node Manager; Tivoli's NetView; Agilent's Advisor and Network Associates' Sniffer.

Written mostly in MODSIM, a strongly typed script language suited to discrete event simulation, EcoPredictor depicts the effects of traffic or topology changes on the network. EcoPredictor's objects include processing nodes, computer groups, various kinds of LAN topologies, applications, transactions and WAN links. Packet flows, which represent the rate of traffic movement rather than the packet size, frequency and distribution, are a key element in EcoPredictor's analysis. In our tests, EcoPredictor and NetRule produced the same simulation results, but EcoPredictor was the slower tool. Compuware says its programmers are rewriting EcoPredictor in C++ for the sake of faster performance as well as the inclusion of a raft of new features in EcoPredictor. The new EcoPredictor Version 8 should be available next year.

EcoPredictor stores its files in a proprietary binary format. Its useful reports show exceptions, recommendations, resource usage analysis and response times. EcoPredictor can also draw charts to show, for example, WAN bandwidth utilization, the top LANs by queue size and the top nodes by network utilization percent.

NetRule is a dream

Essentially a knowledge-based mathematical engine, NetRule is a capacity planner's dream. It's a diagramming tool that quantifies and characterizes details about applications, jobs, transactions, servers, clients, routers, WAN links and other components. NetRule saves design efforts in the form of flat text files you name.

The tool uses the bandwidth, processing speed and other parameters you specify to calculate transaction response times, server utilizations and network utilizations. It can even animate the resulting calculations on the network diagram to visually highlight data flows and potential bottlenecks.

NetRule's calculations are quick and accurate, and the product's reports focus mostly on showing the calculation results in tabular form. The reports include computer costs, delay distributions, job costs, node costs and message delay data.

Visionael offers sophistication

Visionael was the most complex and comprehensive of the products we looked at in this review. In the lab, its discovery feature used SNMP-based software probes to gather network layout and device identification data. Optional Microsoft SMS and HP OpenView software probes can collect data from those respective products. Because Visionael is as much a network and system inventory tool as a design tool, the discovery process collects far more computer and network device detail, such as basic I/O system versions and adapter slot usage, than a network planner needs. During design sessions, the diagramming tool collects this same level of detail about proposed network components. Even while you're designing network changes in Visionael, it continues to monitor the existing network to ensure its baseline data is accurate. In our tests, Visionael stored network component data relationally in an Oracle 8i database. Visionael also offers versions of its product that work with Sybase Adaptive Server or Microsoft SQL Server. The company even publishes the database schema, along with specifications for a Visionael programming interface, for customers that want to add their own functionality to the product. Visionael's reports, which use the bundled Crystal Reports third-party utility, run the gamut from inventory detail to change analysis to WAN circuit details. Visionael also supplies a module for displaying reports as Web pages and can interface with Microsoft Visio.

Visio has friendly wizard

The Enterprise Network Tools option for Visio Professional 2002 adds a great deal more than a set of network diagram icons to Visio. Driven by a friendly wizard, it's a discovery engine that can populate a Visio diagram with existing network components. Design sessions collect computer and network device details that include asset identification and location data, equipment identification data, maintenance and repair data and network data such as IP address and number of ports.

However, unlike EcoPredictor, NetRule and Visionael, Visio's Enterprise Network Tools option collects the same information regardless of whether a network node is a router or a computer. Visio stores its diagramming specifications and network device details in a proprietary binary format. In addition to rendering the network drawing in hard copy or Web page form, Visio can produce Web pages, Visio table shape or XML-based asset reports containing asset types, asset owners, names and manufacturers. Via Open Database Connectivity, Visio can also export data to Microsoft Excel, Microsoft Access or a relational database.

Didyma performs monitoring

While it doesn't have a simulation feature for modeling the behavior of a proposed network design, Didyma has a monitoring function that can periodically ping existing network devices to detect their health. Its discovery feature updates the current design workspace with only the identities of the devices it finds, which makes for even more data entry effort during the design sessions that follow a discovery operation.

Furthermore, as it collects data during a design session, Didyma doesn't distinguish among the various types of network nodes. Whether a node is a computer, router or other device, Didyma, like Visio, asks for the same information. This consists of name, IP address, SNMP community string, interface type (Ethernet, token ring or serial), media access control address, DNS name, whether to monitor the node and whether to include it in reports.

Didyma stores network design data in flat text files.

Didyma's reports, which are based on the product's monitoring feature, show device uptime statistics and device turnaround times. The turnaround times show ping responses for the TCP/IP devices on the network.

Wielding the tools

From a network design perspective, we found EcoPredictor's user interface easy to use but somewhat limiting. It let us work with only one design at a time, although its menuing system and window layout implied the use of Microsoft's Multiple Document Interface technology. EcoPredictor's icons can depict processing nodes, computer groups, generic network devices, subnets, virtual circuits and various LAN topologies. These graphical symbols didn't help us clearly distinguish between, for example, a router and a bridge. Nonetheless, EcoPredictor supports a range of specific device types. The software behaved as we expected when we right-clicked on a network symbol and the process of specifying application and network utilization data was straightforward and quick.

Visio's design environment gave us easy access to multiple windows of concurrent design efforts, clearly distinguished among the different kinds of network nodes (it has separate toolbar icons, for example, for 3Com and Cisco routers) and was the most productive as we diagrammed our proposed network changes. Building our network extensions via Visio was almost completely effortless. The discovery wizard intelligently asked us pertinent questions about the network, such as whether it should look for routers, nonrouter devices and Windows-based devices. Visio also integrates well with the other Microsoft Office products.

NetRule's two-window user interface is quirky. Its left window shows a hierarchical tree view of network component and capacity-planning categories, and, for the currently selected category, the right window contains data or a diagram. Somewhat like a browser's display, NetRule's right window sometimes highlights links you can follow, and the toolbar has back and forward buttons for navigation. However, the browser metaphor doesn't extend to the ability to select and copy text, nor to the use of URLs or recently visited pages. Right-clicking on a NetRule object has no effect. The user interface doesn't rely on dialog boxes containing several related data items. Instead, changing data in the right window involves clicking the data item and entering a new value in a single-entry, pop-up, text-entry window.

To its credit, NetRule has a menu option for opening a new window, which lets you concurrently view multiple aspects of your design. Running a second copy of the NetRule program causes license authorization error messages to appear.

Visionael's Studio module offers an intuitive and comprehensive diagramming interface for specifying changes to the network, but the data entry chores associated with keeping the product's wealth of detail up to date can be daunting. The many property sheet tabs include network attributes, discovered attributes, drawing file, configuration notes, connectivity, selection, vendor, specifications, spec notes, ports, port interfaces, slots, symbols, hierarchy, layout design, layout view and layout details.

Specifying details about devices, cables, raceways and circuits involves a plethora of property sheets and dialog boxes. You can view multiple network designs concurrently with Visionael Studio, in separate windows, and Visionael categorizes network views as historical, “as-built” (the existing network) and what-if. For any view, Visionael displays a hierarchical tree view of devices on the left and a network diagram on the right.

Didyma's rudimentary icons let us distinguish among Sun, Macintosh, Windows and other computers (labeled as PC1, PC2), but we couldn't visually show that one device was a Cisco router while another was a Nortel switch. The program's user interface isn't nearly as quirky as NetRule's, but it has its eyebrow-raisers. For instance, Didyma's dialog boxes don't have cancel buttons for dismissing the dialog. You must instead click the dialog window's upper right corner X. In another oddity, Didyma displays its system requirements in response to choosing the Options/ Requirements menu selection. Why offer to display system requirements to someone who already has the product up and running?

Installing these tools was mostly straightforward. Visionael required that we have licensed and set up our Oracle database before installing the Visionael software, and its three-tier architecture required us to set up separate computers running different Visionael components. All five products enforce strict licensing terms, including product expiration dates, limited access to product functions and, for Didyma, frequent displays of its shareware registration window. Even Visio Professional with Enterprise Network Tools required that we enter two separate product IDs and undergo Microsoft's new over-the-Internet product activation process.

The quality of the documentation varied considerably across these network design tools. Visionael supplies its customers with several well-organized and clearly written printed manuals. Visio and EcoPredictor come with printed manuals, but the manuals don't cover the network design details of the tools. Didyma's terse documentation is only available online, and NetRule's right-hand window can on request show the program's unhelpful and quite terse online documentation. Analytical Engines says that new customers typically learn how to use NetRule over the phone, in a 20- or 30-minute guided tour.


Visionael is a true three-tier Java application that includes a bundled application server environment. Even the Visionael SNMP-based software probes are written in Java. However, a small bit of logic, called the Vael service, runs as a Windows 2000 or NT service on Windows machines.

Based on the product's complexity and price, and because Visionael says its product should occupy at least three computers, Visionael is appropriate for moderately large to enterprise-size networks.

NetRule is a stand-alone Java application with the ability to handle, we estimate, up to tens of thousands of network nodes. We found that EcoPredictor and Visio, both Windows applications, can also successfully handle up to tens of thousands of nodes. In our tests, Visio's discovery process took a long time to finish surveying a 50,000-node network, but the network was quite busy with application traffic during the discovery period, and this may have affected the elapsed time for the discovery process. Didyma, also a Win32 program, is too simple for all but small to midsize networks.


We wished we could've taken the best features of two or more of these tools and merged them. For example, combining Visio Professional with the Enterprise Network Tools option's unparalleled ability to diagram proposed network changes with NetRule's excellent mathematical modeling feature would produce a formidable network design and planning tool. Similarly, interfacing Visionael with EcoPredictor could yield a complete design tool. Although Visionael has a powerful and easy-to-use programming interface, EcoPredictor does not.

Because no tool stood out, selecting EcoPredictor as best network design and planning tool was a compromise among our needs for discovery, design, simulation and documentation. Still, the next time we design changes to a large network, we'll use EcoPredictor to make sure those changes work well.

Compuware EcoPredictor 3.2
Visionael 6.4
Company: Compuware
(800) 521-9353 Price: $27,500. Pros: Intuitive user interface; integrates with EcoScope and many third-party products. Cons: Lacks a discovery feature.
Company: Visionael
(650) 470-8920 Price: Starts at $105,000. Pros: Sophisticated, slick network inventory and design tool; can scale well to handle enterprise-size networks. Cons: Pricey; doesnít have a simulation feature.
Analytical Engines NetRule 4.0
Microsoft Visio Professional 2002 with Enterprise Network Tools
Company: Analytical Engines
(866) 463-8785 Price: Starts at $15,000. Pros:Superior sim-ulation of network capacity and utilization. Cons: Difficult user interface; poor documen-tation; no discovery feature.
Company: Microsoft
(800) 426-9400 Price: $1,000 (upgrade is $750). Pros: Has the widest range of specific device support; intuitive user interface; friendly discovery process. Cons: No simulation of network capacity or utilization.
Bert Houtriet Didyma 1.72
Company: Bert Houtriet Price: $88 (shareware). Pros: Inexpensive; easy to use. Cons: No simulation feature; unsuitable for large networks.

Compuware EcoPredictor Visionael Analytical Engines NetRule Microsoft Visio Professional 2002 with Enterprise Network Toolss Bert Houtriet
Discovery, design, simulation 20% 4 3 4 3 2
Reports 20% 4 4 3 3 2
Ease of use 20% 4 3 3 4 3
Platforms 20% 3 4 4 3 3
Documentation 10% 3 4 2 3 2
Installation 10% 4 3 4 4 4
TOTAL SCORE 3.7 3.5 3.4 3.3 2.6
Individual category scores are based on a scale of 1 to 5. Percentages are the weight given each category in determining the total score. Scoring Key: 5: Exceptional showing in this category. Defines the standard of excellence; 4: Very good showing. Although there may be room for improvement, this product was much better than the average; 3: Average showing in this category. Product was neither especially good nor exceptionally bad; 2: Below average. Lacked some features or lower performance than other products or than expected; 1: Consistently subpar, or lacking features being reviewed.

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Nance, a software developer and consultant for 29 years, is the author of Introduction to Networking, 4th Edition and Client/Server LAN Programming. He can be reached at

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