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Contents Introduction Key Planning Considerations Design Objectives Getting Started General Design Connectivity Issues for Ethernet Servers and Services Conclusion Appendix A: Standards Bodies Appendix B: Tools and Equipment Appendix C: Network Monitoring Tools References/Credits Illustrations Figure 1: Network Layers Figure 2: Network Topologies Figure 3: Hierarchical Star Network Tables Table 1: UTP Wires and Colors Printer Friendly Version Best Practices in Network Design (PDF file, 238 KB) Get Acrobat Reader

Best Practices in Network Design

Servers and Services

Now that you've tackled the basic connectivity issues, there are other decisions to be made about the services and servers you'll need on your network.

File Services: Almost all applications need a place to store data, and most users store their data on their local hard disks. The problem is that when a local hard disk fails, the users lose the data, since local hard disks tend not to get backed up. Additionally, sharing files is difficult without a network. The "sneaker net," that is, using floppies to share information. A file server on a network can virtually solve both these problems. By providing a single place to store data, users are assured that backups are being made of their critical information; users can also share information between themselves with shared filespace. The network administrator can control the rights of the users to access and modify those files and folders for their own private space as well as any public space. All in all, a file server is one of the biggest, most important network resources a network can have.

Print Services: These services allow network users to share printers and to send work to any one of a number of printers in the network. This arrangement cuts costs, as several individuals can share a single (expensive) printer. Users can also access printers they may not have locally (such as a central color laser printer or high-speed printer). It's more cost effective to buy a few good laser printers than to manage a fleet of inkjet printers attached to each user's machine. The increased speed and cost effectiveness of the laser will soon pay for itself.

Web servers: Given the overall trend for services to move to web-based servers, system designers should consider adding a web server to their networks. This server gives people a place to post useful information and to share information in a more public (but still internal) forum. You can also make the server accessible from the Internet to host a public website.

Other servers: Database, application and CD-ROM servers are other possibilities that can provide additional network resources. These are specialized severs that perform specific functions. A database server is quite often the "back end," or engine, for an application and requires its own server. Application servers provide dedicated resources to a specific application, such as an administrative management system (which would also likely require a database server). Finally, many resources exist on CD-ROM that can be shared within the organization without physically sharing the CD, providing security and safety.

Network Operating Systems

Now that we've established the functional requirements and determined the network type (and perhaps some other functions that we need to support), it's time to select a Network Operating System (NOS). The NOS shapes the look and feel of the network and affects what can be done within the network (such as controlling files and folders). The NOS is software that runs on the servers and defines how the network resources are used. By providing the basic operating system environment for the storage of data, control of printing functions and user security, the NOS is the key to a good network.

Novell NetWare (http://www.novell.com)

The elder statesman of network operating systems, NetWare has been around since the early 1980s. NetWare specializes in file and print services and has a very robust security system to manage users. Novell used to run on a network protocol called IPX/SPX; however, with the widespread use of TCP/IP, Novell now operates using either protocol. One advantage of IPX/SPX is that it cannot be routed over the Internet, making services (such as file and print sharing) more secure.

To use NetWare, a computer must be equipped with a NetWare client application, which controls the computer's access to the server and provides the file and printer sharing functions to the desktop OS. Clients exist for Mac OS, Windows (all versions) and Unix.

The security and administration system of NetWare is based on the Novell Directory Services system, or NDS. NDS unifies the entire network and all the resources into a single managed hierarchical structure. Through NDS, an administrator controls file permissions, printer access and other resources. One of the unique features of the NDS is that users don't log into a file server; rather, they log into the network. This configuration allows the NDS database to be distributed across multiple servers, providing redundancy and load sharing in larger networks and keeps the user from worrying about which server to log into.

NetWare is very stable, running for months and even years without a crash (or ABEND, in Novell-speak). Although originally designed for small to medium-sized networks, current versions of NetWare can scale to tens of thousands of users connected to hundreds (or thousands) of network resources.

Microsoft Windows 2000 Server (http://www.microsoft.com)

Microsoft Windows 2000 Server is the biggest head-to-head competitor with Novell's Netware. Beginning with Windows NT, Microsoft began optimizing a server-specific version of it's Windows OS to perform the file, printing and security functions needed to run a network.

Windows uses a set of higher-level network protocols called Server Message Blocks (SMB) that operate with either NetBIOS or TCP/IP (preferred).

Microsoft has also created a suite called Microsoft BackOffice that provides a web server, an e-mail server and a database server, three of the key functions needed in a network.

Active Directory (or NT domains) is how Microsoft manages the network (as opposed to NDS). Multiple computers can participate in a domain, and multiple domains can exist on a network. NDS is more robust and advanced than NT domains, but Active Directory (under Windows 2000) has closed the gap.

Unix

Unix comes in many flavors, from Sun's Solaris to the many Linux distributions. If your network is mostly PCs, be aware that Unix does not offer the full set of services that you would get from Netware or Windows 2000 Server. Unix works well as an application server, especially for databases, and is also used for web servers. Many high-end applications rely on Unix as the server for performance.

Unix can be integrated into the PC/Mac environment using Network File System (NFS) for file sharing; however, the software is expensive to purchase for individual machines. Add-on packages, such as Samba (http://www.samba.org), are free and provide SMB functionality for easier integration into a Mac or PC (Windows) network.

Choosing Hardware

When choosing hardware, try to buy near the top end. Buying top-end equipment will allow your investment to last longer, with minimal additional costs. Over time, additional hard disks or memory may be needed. Be sure to check the memory requirements for the NOS, the applications and the networking client you intend to use—all of which require memory to operate.

When buying a server, buy server-class systems. These units are built with more drive bays, bigger (or even redundant) power supplies and more expansion capabilities than a desktop machine. Servers also offer the ability to use multiple processors, thus improving the performance of the system, especially for database and applications servers.

You can never have enough memory. Make sure your server has plenty of memory, as performance is highly dependent on the available memory. As the load on the server increases, be sure to monitor memory usage and install more before your performance begins to suffer.

On a server, most disk systems are based on SCSI, due to their superior performance. SCSI allows for seven or 14 devices to be "chained" together on a single interface card and makes adding another drive fairly easy. Another disk feature common on servers is RAID, a technique to distribute data storage over several disks to ensure that a single disk failure does not cause data loss. In addition, RAID systems can regenerate the data on the fly from the remaining drives, essentially eliminating downtime when a disk fails. Another controller feature found on SCSI/RAID systems is hot-swap, which allows a drive to be added or replaced without shutting the system down.

Also be sure to back up everything regularly and frequently. Investing in a high-quality tape system and backup software will provide you with the tools to quickly recover from hardware failures as well as software glitches and user errors. Make sure that you keep copies offsite in case of disaster, and periodically test the backups to ensure that you can successfully read the data from the tape.

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