u know it, applications are gasping for bandwidth, response time slows to a crawl, and frustrated users start looking steely-eyed at the network administrator.
Hidden costs associated with poor network designs include overspending on equipment and WAN links to ensure sufficient capacity, trouble reports, poor response to network problems, unpredictable delays in meeting work schedules, and high labor costs for frequent rush jobs.
Fortunately, automated tools are available to help you head off these sorts of problems at the pass. With built-in intelligence, these tools take an active part in the design process (see
"Design's Four Stages"
). With the type of software we'll discuss in this article, you can build a computerized model of
a network; validate its design and gauge its performance; quantify equipment requirements; and explore reliability and security issues before you purchase a single network component. Some of these tools may even identify faulty equipment configurations, design flaws, and standards violations.
Network Designer Tools
Because of the size of the network designs they handle, these tools typically run on Windows NT, Unix, and SunOS. There are two notable exceptions: Supporting Windows 95 (as well as Windows 3.1) are
Network Design
and Analysis's AutoNet, a program for designing T-carrier networks, and American Hytech's NetGuru, for designing LANs and networks of unlimited size.
At the low end, prices for design tools begin at $495 (for NetGuru). At the high end, prices range from $5000 for Image-Net's CANE (Computer Aided Network Engineering) to $15,000 or more for MIL 3's OpNet and Make Systems' NetMaker XA, depending on the type and number of optional plug-in mo
dules. For companies that do not have the time or expertise to learn and use these tools themselves, some vendors, such as Make Systems, offer outsourcing services based on their software; cost of such services starts at $1750 a day.
When working with these tools, you begin the build-a-network process by opening a blank drawing window, into which you can drag various vendor-specific devices -- workstations, servers, hubs, routers -- from a product library and drop them into place (
see the screen
). You can further define the devices by component type, software, and protocols, as appropriate. Lines link the devices to form a network, and each link gets assigned physical and logical attributes. Rapid prototyping provides the ability to copy objects -- devices, LAN segments, network nodes, and subnets -- from one drawing to the next, editing as necessary, until you have built the entire network. Along the way, you can run various simulations to test virtually any aspect of the design.
With the
right tools
, modules, and device libraries, you can design every conceivable type of network, including legacy networks such as Systems Network Architecture (SNA) and DECnet; voice networks including ISDN; and T1, X.25, asynchronous transfer mode (ATM) , and TCP/IP nets. Some tools, such as MIL 3's OpNet, let you incorporate satellite, microwave, and other kinds of wireless technologies.
Starting from Scratch
Designing a large, complex network requires a multifaceted tool, preferably one that is graphical, object-oriented, and interactive. It should support the entire network life cycle, from the definition of user requirements and conceptual design to the detailed vendor-specific configuration of network devices, their protocols, and the various links between them. At each phase, the tool should be able to test design alternatives for cost, performance, and validity. When the design checks out, the tool should spew out network diagrams and a bill of
materials. All this happens before you contact a single equipment vendor or carrier sales rep or write an RFP.
For administrators embroiled in the complexities of network design, this kind of tool represents a dream come true. ImageNet's prerelease version of CANE, an integrated set of Windows NT applications, comes close to meeting this ideal. Designers can take a top-down or a bottom-up approach to network construction. In the top-down approach, the designer starts by sketching out the overall network, then adds increasing levels of detail until every aspect of the network is eventually fleshed out. The bottom-up approach might start with a LAN in a specific department to which you link subsequent drawings to create the overall network structure.
As the drawing window populates, you can further define devices by component type -- such as chassis, interface cards, and daughterboards. You can even specify the operating system, such as "NetWare 3.12 client for a Compaq Presario 660 PC." You can add att
ributes (like protocol functionality) to each device taken from a library. Once you've configured the devices, each device gets a profile that specifies its traffic characteristics for simulating the network's load and capacity.
Having defined each device's configuration, lines between them form the network. CANE then validates the links, testing for common protocols and network functions. This prevents obvious mistakes, such as NetWare clients connecting to other clients instead of servers, for example. This on-line analysis feature also alerts the designer to undefined links, unconnected devices, insufficient available ports in a device, and incorrect addresses in IP networks. An off-line analysis tool reports violations of network integrity and proper network design practices. The designer can analyze the network's structure, its IP completeness, or both at once.
CANE simulates the completed network, using a database that describes how actual network devices behave under various real-world conditio
ns. The simulator generates network events over time, based on the device and traffic pattern recorded in the simulation profile. The designer can test the network's capacity under various "what if" scenarios and fine-tune the network for optimal cost and performance. Simulation in the prerelease version of CANE operates on one LAN segment at a time. By the time you read this, the commercial version of CANE will support fully integrated enterprisewide LAN and WAN simulation.
Better Designs, the "Primitive" Way
The Make Systems design package focuses on building WANs. Among the company's set of six core tools in NetMaker XA is the Designer module. Designer allows you to build cost-effective topology and clocking designs -- from the ground up or incrementally -- using a library of building-block "primitives."
With the time-division multiplexing (TDM) primitives library, for example, you can build an entire T1 network within your specified parameters and constraints. You can strive f
or the lowest transmission cost that supports all traffic, for instance, or for line redundancy between all the TDM nodes. Each primitive addresses a different aspect of the design. You can run tail circuit design, hub selection, or redundancy primitives as needed. You can combine them to address the overall design objectives. You can pause the design process after each design primitive executes to study the results and adjust network parameters if necessary.
Designer uses Planner (another NetMaker tool) to run device-specific simulations to ensure that the network design is feasible and will route all traffic successfully. Since the simulation is vendor-specific (via plug-ins) there is less chance that the network will be overbuilt just to guarantee the handling of all traffic. A tariff database can price transmission links and determine the most economical network design.
The Modeling Approach
Sometimes it's best to approach unfamiliar territory by scoping out the terrain before
committing time and resources to development; this strategy is especially helpful with large networks. Perhaps you want only to assess the feasibility of implementing a certain type of network by playing with a model's various design issues and evaluating the consequences for your organization. MIL 3's OpNet provides standards-based protocol models against which simulations can run within its multilevel development environment. Its model libraries let you do this with a variety of network technologies including frame relay and ATM.
Frame relay, with efficient statistical multiplexing of data and low overhead, has gained broad acceptance in large networks. As frame relay supplements -- and replaces -- legacy technologies such as X.25 and TDM, important issues arise. These issues include the benefits of frame relay versus the benefits of existing network technology, its use with other emerging technologies such as ATM, and its interoperability with higher-level protocols such as TCP/IP.
OpNet's frame r
elay models let you build entire networks -- complete with configurable objects such as routers, switches, and access devices -- so you can study their behavior in great detail. The switch model, for instance, supports the creation of routing tables, switching rate, and buffer capacity for each outgoing link. Among the parameters that can be applied to the permanent virtual circuits (PVCs) are the committed information rate (CIR), committed burst size (Bc), and excess burst size (Be). Incorporating such details into the design allows you to study a variety of network alternatives and assess the impact of new features such as switched virtual circuits (SVCs).
Despite their embedded intelligence, CANE, NetMaker, OpNet, and other stand-alone design products lack the comprehensive automatic discovery capabilities found in heavy-duty management platforms. Hewlett-Packard's OpenView, IBM's NetView/6000, and Sun's Solstice SunNet Manager automatically detect various network elements and represent them with icons
on a topology map. Stand-alone products are better suited for creating new large-scale networks than for changing existing ones, at least for now.
Still, the shape of things to come is apparent in Make System's NetMaker XA 2.5, which can automatically discover frame relay PVCs. Expect autodiscovery to be the next development focus of independent tool makers in the coming year. Meanwhile, high-end stand-alone products still offer more advanced design capabilities. They incorporate a broader range of network technologies and equipment makes and models than the design tools that come with network management systems.
Bargain Power Tool
Developing a large-scale network does not always require high-priced design tools. To plan a large network that has thousands of PCs, workstations, and servers attached to hubs -- interconnected via bridges or routers over IP networks -- you could, for example, use American Hytech's NetGuru, a $495 package that runs under Windows 3.x.
NetGuru allow
s network professionals to design, validate, and document LANs of any size, including ARCnets (
see the screen
). It validates a network design based on standards -- or de facto standards -- with an internal rule-checking knowledge base that you can invoke at any time. The validation ensures that all network components are accounted for -- including network interface cards, converters, terminators, transceivers, multistation access units (MAUs), bridges, repeaters, routers, hubs, and different cable types -- before you start building a network or making additions to one. If a device is misconfigured or a 10Base-T wire exceeds the IEEE standard length, for example, NetGuru alerts you. For the truly adventurous, the program has an expert mode that allows experienced designers to override standards and push the envelope.
NetGuru can be used to design only LANs and large-scale IP networks -- not WANs that include TDM, frame relay, ATM, or wireless technologies. Nevertheless, the program ha
s many features of higher-priced packages, including object orientation and device libraries, drag-and-drop component assembly, simulation capabilities, network documentation, and bill of materials support. An advanced Boolean search engine helps you locate any database element.
Web-Accessible Tools
The Web, besides extending help desk support, configuring and monitoring network devices, accessing network performance data, and enabling and disabling device operations, can also assist with network design.
NetSuite development tools help network professionals design and draw a mammoth network and publish their designs on the corporate intranet or the public Internet. Any authorized user can view them with a Web browser. NetSuite DesignView converts network designs and device details developed in NetSuite Professional Design into hyperlinked Hypertext Markup Language (HTML) documents with device configurations, port usage, and even device photographs. Users can easily navigate from d
evice to device to trace connectivity and review device configurations. Besides supporting fault identification, the hyperlinked documents can be useful when you have to plan design changes.
Achieving specific design objectives requires properly configured equipment at each node. Calico Technology provides a product configurator that interconnect vendors can use to help their systems engineers, value-added resellers, and large customers accurately configure complex, built-to-order products such as routers and hubs.
Cabletron and Cisco are two of the companies that use the Calico Configurator. For example, authorized users can access Cisco's Configurator Agent page on the Web, search for configurable products, choose a particular model, and configure it. A Cisco 7000 backbone router, for example, can be configured for software options, power supply, power cables, memory, route and switch processors, and interface modules. Error messages flash on screen to indicate if you've picked a particular equipmen
t configuration that's invalid, and suggestions help you pick the best configuration. The controls on the page allow you to then send the order to Cisco.
Not Quite Rome in a Day
In simpler days, network gurus kept information systems and networks operating smoothly with all configuration details tucked away in their gray matter. Today, systems are distributed and networks are going global. With intelligent hubs, switched LANs, sprawling router networks, broadband facilities, and advanced services like frame relay and ATM in the mix, large-scale networks are beyond mere human comprehension.
A new generation of intelligent design tools with built-in error detection, simulation and analysis, and plug-in function modules, has finally arrived. Managers and planners needn't be intimately familiar with every aspect of their networks. You can retrieve essential information instantly -- often with point-and-click ease -- then analyze, query, manipulate, and reanalyze that information if ne
cessary. You can display the results in easy-to-understand graphics or export it for further study. Since products differ in the type and scope of data they provide, tools from different vendors may be necessary. Ultimately, the quality and completeness of the data determine the optimal network design.
With these powerful and intelligent new network design tools, you still may not be able to build Rome in a day. But you at least have a chance to build a solid foundation.
Where to Find
American Hytech
Pittsburgh, PA
Phone: (412) 826-3333
Fax: (412) 826-3335
Internet:
http://www.fyi.net/~netguru
Design and Conquer
