Lesson 1:Network Operating Systems

In the past, there was a significant difference between a stand-alone operating system and a network operating system. The typical operating system provided no networking capabilities, and you had to purchase and install networking software to run on it. Today, virtually all operating systems are network operating systems because they include, right in the box, the software needed to connect to a network. This lesson is concerned primarily with operating systems that provide server functions, although in some cases you can also use the server system as a client or a member of a peer-to-peer network.

For more information about the differences between client/server and peer-to-peer networks, see Lesson 1: Network Communications, in Chapter 1, "Networking Basics."

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After this lesson, you will be able to

• List the network operating systems used for server systems
• Describe the basic networking capabilities of Microsoft Windows 2000 Server, Microsoft Windows NT Server, Novell NetWare, UNIX, and the Apple Macintosh operating system

Estimated lesson time: 40 minutes

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Windows NT and Windows 2000

All Windows operating systems except Windows NT and Windows 2000 are built on the MS-DOS kernel. Windows NT 3.1, first released in 1993, was a radical departure from the MS-DOS tradition. It was newly designed from the ground up to support an entirely different memory architecture and to integrate networking capabilities into the operating system itself. In the years since the original release, Microsoft has released several relatively minor Windows NT upgrades, culminating in version 4, and then finally Windows 2000, which was a major upgrade. Windows NT and Windows 2000 also offer preemptive multitasking, which enables the system processor to run multiple programs simultaneously without relying on the programs themselves to return control to the processor.

Windows NT and Windows 2000 have always existed in versions intended both for servers and for client workstations. Windows NT is available in Server and Workstation versions, and Windows 2000 is available in three Server versions (Server, Advanced Server, and Datacenter Server) for systems with various numbers of processors, and a Professional version for client workstations. The underlying kernels of both server and workstation versions are essentially identical; the primary difference between the two is that the server version includes a large collection of additional programs, services, and utilities designed for server use, many of which are concerned with networking. The following sections examine some of these components and how they affect the networking capabilities of the operating systems.

File Systems

Sharing files is one of the main reasons for networking computers, and all network operating systems include a service that makes file sharing possible. One of the most important elements of file sharing is the ability to restrict access to the server files. Windows NT and Windows 2000 both include a file system called the NT file system (NTFS) that is specifically designed for this purpose. The MS-DOS–based versions of Windows use the file allocation table (FAT) file system, and Windows NT and Windows 2000 support FAT, too. You can share FAT drives with other users on the network, but the FAT file system's security capabilities are extremely limited. When you create NTFS drives during a Windows NT or Windows 2000 installation, you can grant access permissions for specific files and folders to the users and groups on your network with great precision, using the controls shown in Figure 4.1. NTFS also supports larger amounts of storage than do FAT drives.

Figure 4.1  The NTFS file system enables a network administrator to control access to files and folders on Windows NT and Windows 2000 drives

For example, if you store your company's accounting spreadsheets on a Windows NT or Windows 2000 NTFS drive, you can grant the bookkeepers full Read/Write access to the files, grant Read-Only access to other company executives, and prevent any other users from even seeing that the files exist. Maintaining these permissions is an important part of the network administrator's job.

NTFS drives can be read only by the Windows NT and Windows 2000 operating systems. If you were to boot a computer with NTFS drives using an MS-DOS boot disk, for example, the drives would be invisible. However, this compatibility issue has nothing to do with access to the drives over the network. Any operating system can access shared NTFS drives, as long as the appropriate permissions are in place.

Services

In Windows NT and Windows 2000 terminology, a service is a program that runs continuously in the background while other operations are running at the same time (see Figure 4.2). Most of the networking capabilities in Windows NT and Windows 2000, and particularly the server functions, are provided by services. In most cases, you configure services to load when the system boots, and they remain loaded and running even when users log on and log off the computer.

Figure 4.2  Windows NT and Windows 2000 include a variety of services that you can configure to load at boot time

The following services are the core of the operating system's networkingcapabilities:

• Server.  Enables the system to share its resources, such as files and printers
• Workstation.  Enables the system to access the shared resources on another computer
• Computer Browser.  Maintains a list of the shared resources on a network from which users can choose
• Messenger.  Enables the system to display pop-up messages about the activities on other network systems
• Alerter.  Works with the Messenger service to notify selected users ofadministrative alerts that occur on the system
• Netlogon.  Provides secure channels between Windows computers for communications related to the authentication process

The following services are optional, but provide important networking support:

• Internet Information Service (IIS).  Provides Internet services, such as World Wide Web and File Transfer Protocol (FTP) servers
• Windows Internet Naming Service (WINS).  Resolves Windows computer (NetBIOS) names into Internet Protocol (IP) addresses
• Domain Name System (DNS) server.  Resolves DNS host names into IP addresses
• Dynamic Host Configuration Protocol (DHCP) server.  Automatically configures Transmission Control Protocol/Internet Protocol (TCP/IP) settings on multiple client systems
• Routing and Remote Access Service (RRAS).  Enables a server to route traffic between two local area networks (LANs) or a wide area network (WAN) and a LAN, and provides support for various routing protocols
• Distributed file system (Dfs).  Enables shared drives on servers all over the network to appear to clients as a single combined share
• Microsoft Cluster Server.  Enables systems running Windows NT 4Enterprise Server or Windows 2000 Advanced Server to operate as part ofa cluster—a group of servers that work together to provide increased performance and fault tolerance

Security

Security is a primary concern on larger networks, and Windows NT andWindows 2000 provide a much more comprehensive security model than do the MS-DOS-based versions of Windows. Windows NT Server and Windows 2000 Server systems have the ability to function as domain controllers, which store information about accounts and other network resources for access by clients anywhere on the network. Using domain controllers instead of individual computers to store security information makes it easier for network administrators to control access to network resources. For more information about domain controllers, see Lesson 3: Directory Services, later in this chapter.

Clients

Windows NT and Windows 2000 servers support connections with virtually every client operating system in use today. All of the Windows operating systems, as well as MS-DOS (with the proper client software installed), can access Windows NT and Windows 2000 servers. With the Microsoft Services for UNIX and Services for Macintosh products installed, UNIX and Macintosh workstations can access Windows NT and Windows 2000 server resources, such as files and printers.

Novell NetWare

Novell NetWare was the first commercially successful network operating system, and although Windows NT and Windows 2000 have eclipsed its popularity, it still remains a viable networking platform. NetWare is strictly a client/server operating system, unlike the Windows NT Server and Windows 2000 Server products, which can function as both clients and servers. This means that you cannot use a NetWare server to access shared resources on other computers or run workstation applications. The NetWare operating system is not DOS-based (although it does load from a DOS prompt), and it is dedicated solely to server operations. NetWare clients communicate only with NetWare servers and not with each other. To transfer files from one workstation to another, for example, you must copy them from the first workstation to a server, and then from the server to the other workstation.

It is possible, however, for a computer running a NetWare client to run a Windows networking client at the same time, enabling it to access Windows network resources also.

There are two primary versions of NetWare, 3.2 and 5.1. Version 3.2 was the final release of the original NetWare product that stores user account information in a simple flat database called the bindery. Novell Directory Services (NDS) replaced the bindery in NetWare version 4.0 (released in 1993). Novell discontinued version 3.2 in October 2000, but it still has a large installed user base that does not need the more advanced capabilities of NDS, and many of these users have no plans to upgrade their networks. Version 5.1 is the current release of the NDS-based NetWare product that began with version 4.0.

NetWare is a network operating system that was originally designed primarily to provide clients with access to file and print services, and these remain NetWare's primary strengths. As a network application platform, NetWare trails behind both Windows and UNIX, and there is comparatively little application development for NetWare.

Novell Directory Services is NetWare's greatest strength. NDS is a full-featured directory service that was released in 1993, and has thus had a long time to mature. Microsoft's equivalent directory service, called the Active Directory service, was released in 2000. For more information about NDS, see Lesson 3: Directory Services, later in this chapter.

Because they do not have to perform workstation operations, NetWare servers have a relatively simple, character-based interface, as shown in Figure 4.3. There is no need for a graphical interface on a server (although the most current versions have an optional Java-based interface called ConsoleOne that you can use), and as a result, the computer can devote fewer of its resources to maintaining a graphical display and more to performing its server functions.

Like Windows NT and Windows 2000, NetWare has its own file system that enables you to control access to the server resources with great precision. You can assign access permissions based on either bindery accounts or NDS objects, depending on which version of NetWare you are using. The NetWare file system consists of volumes that you create on server drives. By adding specialized components called name space modules, you can create NetWare volumes that support various client file systems, such as Windows Virtual File Allocation Table (VFAT), Macintosh, and Network File System (NFS). This enables clients to store their files on NetWare servers using their own native formats.

Figure 4.3  The NetWare server console is character-based, but uses keyboard-driven menus

NetWare Protocols

When NetWare was first developed in the mid-1980s, networking was more of a proprietary venture, and interoperability between products made by different manufacturers was less of a concern than it is today. Novell, therefore, developed their own set of networking protocols, which have come to be named after the main network layer protocol, called Internetwork Packet Exchange (IPX). Unlike Windows NT, Windows 2000, and UNIX, which have long since adopted the TCP/IP suite as their native protocol, NetWare still relies heavily on IPX. Fortunately, Microsoft has developed its own protocol, called NWLink, to be compatible with IPX. All of the Windows operating systems can use NWLink to access shared NetWare resources.

For more information about the IPX protocols, see Chapter 6, "Network Layer Protocols," and Chapter 7, "Transport Layer Protocols."

NetWare Services

In addition to its core file and print services, which have been present since the early days of NetWare, the latest versions of the software include many other services, such as the following:

• Novell Storage Services (NSS).  This is a 64-bit, indexed storage service that enables administrators to use the storage space on multiple drives to createan unlimited number of logical volumes up to 8 terabytes in size. (A terabyte is approximately 1 trillion bytes, or more precisely, 1,099,511,627,776 bytes.)
• Novell Distributed Print Services (NDPS).  This is a new network printing architecture that replaces NetWare's traditional queue-based printing with a single printer object in NDS that provides simplified, centralized administration.
• NetWare Internet servers.  NetWare includes Web, FTP, News, and Multimedia Servers, as well as a Web Search Server that indexes Web sites for easier client access.
• DNS and DHCP servers.  NetWare now supports TCP/IP in addition to IPX, and it includes DNS and DHCP servers that can resolve host names into IP addresses and configure TCP/IP clients, all from the NetWare platform.
• Multiprotocol WAN router.  This service enables a NetWare server to route multiple network layer protocols between two LANs or between a LAN and a WAN. You can use the router to connect private networks or to connect a network to the Internet.

UNIX

UNIX is a network operating system originally developed in the 1970s, now available in dozens of different versions and variants. Unlike Windows and NetWare, UNIX is not the product of one particular company. A variety of different development teams worked on their own UNIX versions during the ensuing decades, which were released under many different names, including the following:

• UNIX System V.  This is the descendent of the original UNIX development program started by AT&T in the 1970s. The UNIX trademark has changed hands several times over the years, and UNIX System V is now owned by The Santa Cruz Operation, Inc. (SCO).
• Berkeley Software Distribution (BSD) UNIX.  BSD UNIX was one of the first variants to splinter off from the original AT&T development effort, and it has become one of the most consistently popular UNIX products. The most popular BSD UNIX versions today are FreeBSD, OpenBSD, and NetBSD, all of which are open source products, which means that the operating systems and their source code are available for download from the Internet free of charge.
• Sun Solaris.  Sun Microsystems markets Solaris, one of the most popular and user-friendly commercial UNIX operating systems available. Solaris is essentially a modified version of BSD UNIX with elements of SVR4, one of the progenitors of UNIX System V. Solaris also includes Open Windows, one of the better graphical interfaces for UNIX.
• Linux.  Linux is a UNIX-based subculture unto itself, in that there are many different versions, both free and commercial. Originally developed as a school project by a student named Linus Torvalds, Linux is the quintessential open source operating system, because its development and maintenance was almost totally a noncommercial collaboration until quite recently. There are now some Linux versions sold as commercial products with documentation and technical support, but others are still available free of charge.
• Hardware-specific UNIX variants.  Several manufacturers of computer hardware have developed their own UNIX variants, designed specificallyto run on their computers. These include Hewlett Packard's HP-UX and IBM's Advanced Interactive Executive (better known as AIX).

Whereas NetWare runs solely on computers with Intel-based processors, and Windows NT and Windows 2000 run on the Intel and Alpha platforms, the various UNIX operating systems run on computers with a wide variety of processors, including Intel, Alpha, Sun Microsystems' proprietary SPARC processor, and others.

The UNIX operating systems are built around the TCP/IP protocol suite, andalthough all have some similarities, they vary greatly in their capabilities due to the variations in the additional software included with the operating system and the commercial (or noncommercial) nature of the various products. Some UNIX variants are commercial products marketed by large software companies, such as Hewlett Packard, Sun Microsystems, and IBM. Others are developed and maintained as part of the open source movement, in which volunteer programmers work on the software in their spare time, usually communicating with their colleagues over the Internet, and freely releasing their work to the public domain. There are many different UNIX operating systems that you can download from the Internet free of charge, such as FreeBSD, NetBSD, and various forms of Linux.

This noncommercial side of UNIX development is based on the fact that many of the development teams freely post the source code for the operating system. Users with programming expertise then modify the code to suit their particular needs and post the revised code for use by others. This is in stark contrast to the work of companies like Microsoft and Novell, who zealously guard the source code for their operating systems.

UNIX is primarily an application server platform, typically associated with Internet services, such as Web, FTP, and e-mail servers. As with Windows NT and Windows 2000 systems, UNIX systems can function as both servers and clients simultaneously. You can use UNIX as a general-purpose LAN server, but it is much more difficult to install and administer than either Windows or NetWare. There are UNIX programs that provide the file and print services needed by LAN users, such as the NFS and the line printer daemon (LPD), but they are far from being as easy to use as their Windows NT, Windows 2000, and NetWare equivalents. NetWare's strength is in file and print services, and the strength of UNIX is in its network application capabilities. Windows NT and Windows 2000 fall somewhere between the two, fulfilling both roles but doing neither as well as the more specialized operating systems.

Daemon is the UNIX term for an application that runs continuously in the background, like a service in Windows NT or Windows 2000.

UNIX, in general, is a less intuitive operating system than either Windows or NetWare. Although many UNIX variants now include graphical user interfaces (GUIs), UNIX is still primarily a character-based platform, and the command interface requires a good deal of study and practice to use efficiently. A relativelyunsophisticated user can install a Windows NT, Windows 2000, or NetWare server and get it running without too much trouble, but the same cannot be said for the typical UNIX operating system.

The UNIX operating systems use the peer-to-peer networking model and are based on a small kernel, similar in most of the variants, which is enhanced by the addition of processes such as applications and services. Some of the services that provide UNIX with its networking capabilities are common to nearly all of the UNIX versions, such as NFS, which enables systems to share and access shared files, and familiar networking tools like FTP and Telnet. Because these services are based on TCP/IP protocol standards, other operating systems can use them to interact with UNIX computers.

Macintosh

Apple Macintosh computers have included networking capabilities virtually since their inception. Macintosh computers have long included a network interface called a LocalTalk adapter as part of their standard equipment, and the MacOS operating system includes a proprietary protocol suite called AppleTalk. AppleShare is a file and printer sharing solution that enables a Macintosh computer to function as a server and provides the security features needed to password-protect data resources and monitor network activity. The computers on a Macintosh network are divided into zones, which are essentially organizational units that make it easier to locate network resources. Together, these components provide basic networking capabilities that are suitable for joining a handful of Apple computers into a network and sharing files and printers. The performance of an all-Apple network is rudimentary and not designed for heavy traffic, but it does enable Macintosh computers to share resources.

As the years passed, Apple, along with the rest of the computer networking industry, moved away from their proprietary solutions and toward recognized standards. You can now run network interface adapters that use Ethernet and Token Ring on Macintosh systems using data-link layer protocols called EtherTalk and Token Talk, respectively. In addition, Apple has ceased development of the AppleTalk protocols and is concentrating more on TCP/IP for network transport services, using products such as Apple Open Transport and AppleShare IP. Because of the universal desire to connect to the Internet, MacOS now uses TCP/IP as its default network protocol suite. As a server platform, Macintosh lacks the broad-based application support found in Windows and UNIX, but with the proper hardware, it can be a good performer. In most cases, however, Macintosh computers are used as servers on all-Macintosh networks. It isn't common to see a Windows or UNIX shop use Macintoshes as servers.

Exercise 1: Network Operating System Products

Match the network operating system in the left column with the phrase in the right column that best describes it.

1. Linux
2. Windows NT
3. Macintosh
4. UNIX System V
5. NetWare 3.x
6. Windows 2000

1. Uses a bindery to store user accounts
2. Current version of the original AT&T UNIX
3. Available in Server, Advanced Server, and Datacenter versions
4. First version of Windows not based on MS-DOS
5. Originally used a proprietary data-link layer protocol
6. Open source UNIX version

Lesson Review

1. What is name of the Windows NT and Windows 2000 file system that enables administrators to assign permissions to individual files?
   1. Active Directory
   2. NDS
   3. FAT
   4. NTFS
2. Which of the following services on a Windows NT or Windows 2000 network is responsible for configuring TCP/IP clients?
   1. DNS
   2. WINS
   3. DHCP
   4. IIS
3. Which of the following network operating systems is generally considered to be the best application server platform?
   1. Windows NT
   2. UNIX
   3. Windows 2000
   4. Novell NetWare
4. What is a program called that runs in the background on a UNIX system?
   1. A service
   2. A daemon
   3. An application
   4. A domain
5. What is the name of the Windows NT and Windows 2000 service that maintains a list of shared resources on the network?
   1. Server
   2. Client
   3. Computer Browser
   4. Messenger

Lesson Summary

• The Windows NT, Windows 2000, and UNIX operating systems all include both server and client functionality.
• NTFS is a file system that enables network administrators to control access to shared files and folders.
• Many of the Windows NT and Windows 2000 networking functions are performed by services.
• Novell NetWare is strictly a client/server network operating system.
• Early versions of NetWare used a bindery to store user accounts, and later versions use Novell Directory Services.
• UNIX is available in many different versions produced by different companies.
• UNIX systems excel in running network applications. NetWare's strength is file and print services. Windows NT and Windows 2000 can fulfill both roles.
• Macintosh computers have included rudimentary proprietary networkingcapabilities from the beginning but are now conforming to industry networking standards.