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."
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.
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.
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:
The following services are optional, but provide important networking support:
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.
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 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
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."
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:
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:
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.
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.
Match the network operating system in the left column with the phrase in the right column that best describes it.
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