Networking

Contents

1. Planning a Logical Network Design

2. Planning and Design Components

3. The Physical Network

4. Planning Resources

Article Description

Scott Mueller and Terry Ogletree talk about your network's logical and physical design, including planning and components of a logical network design, the physical network, and planning resources.

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Upgrading and Repairing Networks, 4th Edition

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Some of the Main Topics in this Chapter Are

* Planning a Logical Network Design

* Planning and Design Components

* The Physical Network

* Planning Resources

Many types of networks were discussed in Chapter 1, "A Short History of Computer Networking," from ARCnet to TCP/IP. And in Chapter 2, "Overview of Network Topologies," you learned about the various topologies you can employ when designing and creating a local area network (LAN), and we also looked at some scenarios in which several networks were connected to form a wide area network (WAN). In this chapter, we will look at another aspect of creating a network: the network's logical and physical design. The physical aspects of your LAN will depend on the underlying physical transport technology--Ethernet or Token-Ring, for example, or possibly ATM, which is now supported in products such as Windows 2000/XP and Server 2003 as a LAN protocol. Depending on which technology you use, there will be one or more LAN topologies from which to choose.

NOTE

Although there are other LAN technologies, such as ARCnet and Novell's IPX/SPX, these are basically legacy products that are no longer being deployed in newer networks. For example, ARCnet is now used mostly in vertical-market applications (such as on the factory floor, or for point-of-sale cash registers). If you don't need the features that TCP/IP provides, and don't need an Internet connection, then these older protocols may be a good solution for your network. Novell's NetWare products, while allowing for backward compatibility with the IPX/SPX protocol, have finally caught up with the times, and new installations will more than likely use the IP protocol. Other protocols, such as Microsoft's LAN Manager, are used only in older networks. If you are still using older proprietary protocols, you should consider upgrading to TCP/IP, which is now the de facto standard, from the worldwide Internet down to the LAN.

Before you can begin to design a physical network, however, you first must determine your needs. What services must you provide to your user community? What are the resources you'll need? If you have to compromise, what will it take to satisfy the most users or to provide the more important services? You then will have to take into account network protocols, applications, network speed, and, most important, network security issues; each of these figures into a network's logical design. Another important factor your management will probably force you to consider is cost--you can't forget the budget. These factors make up the logical design for your network. You first should decide what you need and what it will take to provide for those needs.

If you are creating a new network and purchasing new applications, you will probably spend most of your time considering the licensing and other financial costs (training users, network personnel, and so on). If you are upgrading older applications, several other factors come into consideration. Many applications that were coded using COBOL, BASIC, FORTRAN, and other languages that helped jumpstart the computer age may have built-in network functionality based on older proprietary network protocols. If this is the case with your network, you have to consider several things. What will it cost to update thousands of lines of code (or more) to more modern versions of the same programming language? What will it cost to upgrade these programs to newer object-oriented languages? To save money, can you upgrade part of your network and use gateway hardware/software to connect to older network components?

Because of the costs associated with coding applications that were created many years ago, and the expenses that will be required to update them to modern programming languages, you may be forced to maintain legacy applications for a few years while replacement applications are designed and created. You may find a packaged application that can be used to replace older programs. This problem will apply mostly to proprietary computer architectures, instead of Windows or Unix platforms. If you can simply make minor changes and compile the source code so that it will run on a newer operating system, your costs will be much less than if you have to re-create the applications your users need from scratch. Another cost associated with upgrading to new programs is training users and help-desk personnel.

Planning a Logical Network Design

When you plan a logical network design, you can start from one of two places. You can design and install a new network from scratch, or you can upgrade an existing network. Either way, you should gather information about several important factors before you begin the logical design. For example, depending on the services that will be provided to clients, you might need to analyze the possible traffic patterns that might result from your plan. Locate potential bottlenecks and, where possible, alleviate them by providing multiple paths to resources or by putting up servers that provide replicas of important data so that load balancing can be provided. The following are other factors to consider:

* Who are the clients? What are their actual needs? How have you determined these needs--from user complaints or from help-desk statistics? Is this data reliable?

* What kinds of services will you provide on the network? Are they limited in scope? Will any involve configuring a firewall between LANs? And if so, that still doesn't account for configuring a firewall to enable access to the Internet.

* Will you need to allow an Internet connection for just your internal network's users, or will use you need to allow outside vendors access to your network? One example that comes to mind is the Internet Printing Protocol (see Chapter 25,