One of the most important design issues for an organization is the selection of a network operating system (NOS). This choice will affect the low-level network protocols that you will use, the way that the servers are administered and the way that users interact with network services. The NOS shapes the entire look and feel of the network environment. The NOS marketplace is very mature. The choices available, while relatively few, offer sophisticated features, high reliability, and relatively easy setup and administration.

The NOS is the software that runs on servers and defines how resources are shared on the network. It provides the basic operating environment for the server so that it can store data in a secure, reliable way, and satisfy requests from a large number of users simultaneously. Each NOS on the market today relies on extremely sophisticated multitasking, multiuser operating systems with many features designed to optimize performance, control access and ensure a high level of security. The NOS includes a set of tools the network administrator uses to configure the resources on the server as well as utilities for client computers to access those resources. At a minimum, an NOS offers file storage and network printing services. Most also offer the ability to run other specialized network-oriented applications.

Current NOS choices include Novell NetWare, Microsoft Windows NT Server and various Unix-based systems.

Novell NetWare

Novell NetWare, developed in the early 1980s as one of the first network operating systems, continues to be a major player. NetWare specializes in file and print servers. Novell networks rely on a set of underlying low-level network protocols called IPX/SPX (Internet Packet eXchange/Sequenced Packet Exchange). These protocols operate well with either Ethernet or token-ring networks, and are supported by almost all routers and other network equipment.

While widely supported, IPX/SPX today lacks the universal support enjoyed by TCP/IP. As the protocol of the Internet, TCP/IP has quickly become the dominant protocol in local networks as well. TCP/IP and IPX/SPX can operate simultaneously on a network. Many organizations use IPX/SPX for file and print service, and TCP/IP for Web-based services. Since IPX/SPX cannot be routed over the Internet, having local services based on these protocols makes them less susceptible to external attacks from hackers. NetWare is evolving toward greater support for TCP/IP. NetWare servers can run TCP/IP in addition to IPX/SPX and support Internet-style services such as Web and FTP servers. Through NetWare/IP, file and print services can operate over IP. Future versions of NetWare will embrace TCP/IP natively, allowing NetWare to operate in networks that do not allow IPX/SPX at all.

To access a NetWare server, a computer must be equipped with the proper network client software. Novell offers clients that can be installed for all major operating systems, including Windows 95, Windows NT, Windows 3.x and MacOS. Microsoft includes its own Client Services for NetWare in Windows 95 and Windows NT, so that these computers can access NetWare servers without any additional software.

In addition to file and print services, NetWare servers support other applications in the form of NetWare Loadable Modules, or NLMs. Compared to Windows NT or Unix, there are relatively few NLM applications. NetWare excels much more as a file server than as an applications server.

One of the fundamental features of the current generation of NetWare is NetWare Directory Services (NDS). This directory structure unifies all network resources into a hierarchical system. Through NDS, a network administrator defines what resources each user can access throughout the network. Novell provides a graphical application called NWAdmin that a network administrator uses to define all the resources in the NDS environment.

NDS allows users to log in once to the NDS tree and gain access to a variety of resources, even when they're physically dispersed across different servers. Previous versions of NetWare relied on a database, called the Bindery, that defined access to resources on each individual server, and users would need to log in separately to each server to gain access to its resources.

NetWare has a reputation for being extremely stable and reliable. Once set up properly, a NetWare server will operate practically indefinitely without a crash (or ABEND in Novell's terminology).

Novell NetWare was originally designed for small to medium-sized businesses, back when mission-critical functions ran on mainframe computers. Over time, the use of mainframe systems diminished and NetWare evolved to the point where it could easily support enterprisewide networks. Today, NetWare tends to be associated with large networks. Through NDS, organizations can have dozens or hundreds of NetWare servers supporting thousands of users.

Novell continues to court small-office networks. IntranetWare is a suite of products that includes the basic NetWare 4.11 operating system plus a number of applications that Novell once marketed separately. IntranetWare includes a Web server, an FTP server, NetWare/IP, the Novell Muitiprotocol Router, and the GroupWise applications for electronic mail and group calendars. IntranetWare for Small Business is a specially configured version of this applications suite, designed for easy installation and administration. IntranetWare for Small Business is much easier to install than the regular version through a set of wizards that guide the installation process. See http://www.novell.com/intranetware/products/smallbiz/ for more detailed information.

Microsoft Windows NT Server

Windows NT has steadily risen to challenge NetWare's position as the dominant NOS. It offers file and print services, and excels as an network applications server. Microsoft offers both Server and Workstation versions of Windows NT. While these products have many similarities, the NT Server has been optimized to operate as a high-performance network server and includes many security features not found in NT Workstation.

Windows NT uses a set of higher-level network protocols called Server Message Block (SMB) that operate with either NetBIOS or TCP/IP lower-level protocols. Windows NT can be easily configured to operate in a pure TCP/IP environment.

NT has become a very popular platform for network applications. Software written for DOS, 16-bit Windows or 32-bit Windows all run under Windows NT. Applications can be written to run as a native NT service to integrate fully into this environment.

Microsoft offers a package called Microsoft BackOffice for Small Business designed for the networking needs of organizations with less than 25 users. This product includes Windows NT Server, plus Microsoft Internet Information Server for Web services, Microsoft Exchange server to support electronic mail and Microsoft SQL server for database applications.

A Windows NT network uses the Domains concept to tie the network together. Multiple computers can be part of a domain, and multiple domains can exist on a network. NT version 5.0 will have a more advanced approach for organizing the network called the Active Directory. While Microsoft's domain system is generally considered less advanced than Novell's NDS architecture, it is certainly adequate for the needs of a small business network. Both Novell and Microsoft would argue fiercely about which approach to network services is superior, but either method would easily handle the challenge of organizing the small networks under consideration here.

NT servers are relatively easy to set up and administer. Any advanced user proficient with Windows 95 or with NT Workstation should be able to learn the basics of NT server with a little bit of effort. All the tools for managing an NT server are easy-to-use graphical applications.

Unix

The third main NOS alternative is comprised of the various flavors of Unix, including Solaris from Sun Microsystems. If your company uses mostly PCs, Unix does not offer the full set of services of NetWare and NT. Unix systems work well as network application servers and are widely used as Web servers and database servers. Many high-end client/server applications rely on Unix for their server.

Unix does not work well as a file server for PCs. The native means for sharing files with Unix servers involves the use of NFS or DFS, which do not come with any of the Windows or Macintosh operating systems. While NFS and DFS clients can be added to PCs through third-party applications, doing so can be expensive.

Unix has a reputation for being more difficult to install and support than either NetWare or NT. But many individuals have experience with Unix. Linux, a freeware version of Unix, has become extremely popular, and many people interested in developing their computer skills have used this operating system to gain experience with Unix.

Most small business should consider using Unix only if they have industry-specific applications that require it. Unix servers tend to be used in addition to, not in place of, an NOS such as NetWare and Windows NT. In an enterprise network, file and print services might be managed through NetWare or NT, while the organization's Web servers and database servers would be based on Unix servers. In a small network, there is a tremendous benefit to running applications servers on the same operating environment as the file servers to avoid additional system administration overhead.