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LESSON 7BENEFITS OF NETWORK OPERATING SYSTEM

IntroductionNetwork Operating System is also called a NOS. It is anoperating system which includes software to communicate withother computers via a network and manages network resources.It manages multiple requests (inputs) concurrently and providesthe security necessary in a multiuser environment. It may be acompletely self-contained operating system, such as NetWare,UNIX and Windows NT, or it may require an existing operat-ing system in order to function (LAN Server requires OS/2;LANtastic requires DOS, etc.).

ObjectiveOn completion of this lecture, students would able to knowthe operations and benefits of networking operating system.

NETWORK OPERATING SYSTEMOne piece of the network operating system resides in each clientmachine and another resides in each server. It allows the remotedrives on the server to be accessed as if they were local drives onthe client machine. It allows the server to handle requests fromthe client to share files and applications as well as networkdevices such as printers, faxes and modems.In a peer-to-peer network, the network operating system allowseach station to be both client and server. In a non-peer-to-peernetwork, dedicated servers are used, and files on a clientmachine cannot be retrieved by other users.In networks of PCs, NetWare is the most widely used networkoperating system. Windows NT, Windows for Workgroups,Windows 95/98, VINES, LAN Server, LAN Manager andLANtastic are also examples.UNIX, combined with TCP/IP and NFS, VMS combined withDECnet, the Mac OS combined with AppleTalk, and SNA,combined with VTAM and NCP, also provide networkoperating system services.Along with file and print services, a network operating systemmay also include directory services and a messaging system aswell as network management and multiprotocol routingcapabilities.

1.12.1 EXAMPLES OF OPERATING SYSTEMS

NetWare

A family of network operating systems from Novell thatsupport DOS, Windows, OS/2 and Macintosh clients. UNIXclient support is available from third parties. NetWare is thelargest installed base of LAN operating systems.Except for Personal NetWare and NetWare ELS, which wereearlier peer-to-peer versions, NetWare is a stand-alone operatingsystem that runs in the server. Until NetWare 5, which nativelysupports TCP/IP and Java, NetWare has always been aproprietary system. NetWare’s native communications protocolsare IPX, SPX and NCP. Its hard disks are formatted with the

NetWare format, and although DOS and Windows applicationsreside in the server, they cannot be run in the server. Allprograms that run on a NetWare server are typically written in Cand must be compiled using Novell libraries into executablefiles known as NetWare Loadable Modules (NLMs).Introduced in late 1998, the latest version is NetWare 5. FullyTCP/IP and Java based, Novell added significant enhancementsto its flagship product, including a kernel that natively supportssymmetric multiprocessing (SMP).Introduced in 1993, NetWare 4 was the first NetWare version touse the much-acclaimed Novell Directory Services (NDS), whichprovides directory services for a global enterprise.Introduced in 1989 as NetWare 386 and then again in 1992 asNetWare 3.11, it was the first 32-bit version of NetWare, whichhas a limit of 250 concurrent users. Still being sold, it uses theNovell bindery which provides directory services for a singleserver unlike the global NDS directory. NetWare 2.x (originallyAdvanced NetWare 286 in 1985) ran in a 286 and supported upto 100 concurrent users. See IPX, SPX, NCP and MHS.

UNIXPronounced yoo-niks, it is a multiuser, multitasking operatingsystem that is widely used as the master control program inworkstations and especially servers. Myriads of commercialapplications run on UNIX servers, and most Web sites rununder UNIX. There are many versions of UNIX, and, exceptfor the PC world, where Windows dominates, almost everyhardware vendor offers it either as its primary or secondaryoperating system. Sun has been singularly instrumental incommercializing UNIX with its Solaris OS (formerly SunOS).HP, SCO, IBM and Digital have also been major UNIX vendorsand promoters.UNIX is written in C. Both UNIX and C were developed byAT&T and freely distributed to government and academicinstitutions, causing it to be ported to a wider variety ofmachine families than any other operating system. As a result,UNIX became synonymous with “open systems.”UNIX is made up of the kernel, file system and shell (com-mand line interface). The major shells are the Bourne shell(original), C shell and Korn shell. The UNIX vocabulary isexhaustive with more than 600 commands that manipulate dataand text in every way conceivable. Many commands are cryptic(see below), but just as Windows hid the DOS prompt, theMotif GUI presents a friendlier image to UNIX users. Command UNIX DOS List directory ls dir Copy a file cp copy Delete a file rm del Rename a file mv rename

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Display contents cat type Print a file lpr print Check disk space df chkdsk Change directory cd cd

The History of UNIXUNIX was developed in 1969 by Ken Thompson at AT&T,who scaled down the sophisticated MULTICS operating systemfor the PDP-7. The named was coined for a single-user version(UNo) of “multIX.” More work was done by Dennis Ritchie,and, by 1974, UNIX had matured into an efficient operatingsystem primarily on PDP machines. UNIX became very popularin scientific and academic environments.Considerable enhancements were made to UNIX at theUniversity of California at Berkeley, and versions of UNIX withthe Berkeley extensions became widely used. By the late 1970s,commercial versions of UNIX, such as IS/1 and XENIX,became available.In the early 1980s, AT&T began to consolidate the many UNIXversions into standards which evolved into System III andeventually System V. Before Divestiture (1984), AT&T licensedUNIX to universities and other organizations, but wasprohibited from outright marketing of the product. Afterdivestiture, it began to market UNIX aggressively.

Advantages of UNIXEven with its many versions, UNIX is widely used in missioncritical applications for client/server and transaction processingsystems. UNIX components are of world class standards. TheTCP/IP transport protocol and SMTP e-mail protocol are defacto standards on the Internet. NFS allows files to be accessibleacross the network, NIS provides a “Yellow Pages” directory,Kerberos provides network security, and X Window lets usersrun applications on remote servers and view the results on theirmachines.

Windows NT(Windows New Technology) An advanced 32-bit operatingsystem from Microsoft for Intel x86 and Alpha CPUs. Supportfor the PowerPC and MIPS platforms was dropped. Introducedin 1993, NT does not use DOS, it is a self-contained operatingsystem that runs 16-bit and 32-bit Windows applications aswell as DOS applications.There are actually two versions of Windows NT: Windows NTServer, designed to act as a server in networks, and WindowsNT Workstation for stand-alone or client workstations.Features include peer-to-peer networking, preemptivemultitasking, multithreading, multiprocessing, fault toleranceand support for the Unicode character set. NT providesextensive security features and continually tests the validity ofapplication requests even after the application has been opened.Windows NT supports 2GB of virtual memory for applica-tions and 2GB for its own use. Windows NT and WindowsNT Workstation are the first and second releases of the clientversion. Windows NT Advanced Server (NTAS) and WindowsNT Server (NTS) are first and second releases of the serverversion, which supports symmetric multiprocessing (SMP) and

provides transaction processing for hundreds of online users.NT includes a dual boot feature.NT Server is being widely implemented. NT’s SMP capabilitytakes advantage of Pentium Pro and Pentium II systems thatcontain two, four and more CPUs. As these multiprocessorsystems become mainstream, NT competes squarely againstRISC-based multiprocessor servers running UNIX. NTWorkstation is also gaining market share in high-end desktopsystems.The last version of Windows NT with the Program Managerinterface was Version 3.51. Introduced in the summer of 1996,Windows NT 4.0 contains the Windows 95 user interface.There are differences in some of the dialog boxes as NTcontains features not available in Windows 95, and vice versa.NT 4.0 also includes Microsoft’s DCOM interface that allowsapplications to be distributed across the network. NT 4.0 doesnot support Plug and Play, as does Windows 95.NT Server 4.0 comes with Microsoft’s Internet InformationServer (IIS), which provides Web server capability.NT Version 5.0, which was renamed Windows 2000, is expectedin 1999. It adds Plug and Play support, Direct3D support,Active Directory, Zero Administration for Windows (ZAW)and other enhancements. Version Date/Intro 3.1 July 1993 3.5 Sept 1994 3.51 Aug 1995 4.0 Aug 1996 2000 1999

1.12.2 Benefits of Network Operating SystemA network operating system (NOS) causes a collection ofindependent computers to act as one system. A networkoperating system is analogous to a desktop operating systemlike DOS or OS/2, except it operates over more than onecomputer. Like DOS, a network operating system works behindthe scenes to provide services for users and application pro-grams. But instead of controlling the pieces of a singlecomputer, a network operating system controls the operationof the network system, including who uses it, when they canuse it, what they have access to, and which network resources areavailable.At a basic level, the NOS allows LAN users to share files andperipherals such as disks and printers. Most NOSs do muchmore. They provide data integrity and security by keepingpeople out of certain resources and files. They have administra-tive tools to add, change, and remove users, computers, andperipherals from the network. They have troubleshooting toolsto tell LAN managers what is happening on the network. Theyhave internetworking support to tie multiple networkstogether.

RedirectionAt the heart of the NOS is redirection. Redirection is takingsomething headed in one direction and making it go in adifferent direction. With redirection, an operating program doesnot know or care where its output is going.

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GYou are probably familiar with DOS redirection. For example,the DOS command DIR > FILENAME will redirect a directorylisting to a file instead of to the screen. The “>” tells DOS togive the results of the command to the entity on the right.Network operating systems depend heavily on redirection, onlyin this case data is being redirected from one computer toanother over the network cable, not over the PC’s bus to localfiles or printers. Nevertheless, the operation is similar. If youtype “COPY C: FILEA F:”, FILEA will be copied from yourlocal drive C: to the network drive F:. The NOS makes it appearto the COPY command that drive F: is local, when it reallyresides on another computer that is attached to the samenetwork. The COPY command doesn’t know or care that driveF: is across the network. It sends the file to DOS and the NOSreroutes the file across the LAN to drive F:.Redirection can be done with printers and other peripherals.Thus, LPT1: or COM1: can be a network printer instead of alocal printer and the NOS redirects file to these devices. With aNOS, users don’t need to know about redirection; they justtype the drive designator or print from their word processors asalways.

Server SoftwareThe computer with drive F: must expect data, if the outputfrom the user’s PC can be redirected successfully. To do this, itmust make its drive available to network users. This is part ofthe NOS’s function at the server.A NOS is made of a redirector and a server. Not all machinesneed to run the server software, because not all computers needto share their resources. But all LAN workstations must runredirector software because every client has to be able to put dataonto the network.With some NOSs, the computer running the server softwarecannot be used as a workstation. This is called a dedicatedserver. Novell’s NetWare uses this kind of setup almostexclusively (although the low-end NetWare Lite can usenondedicated servers). With some other NOSs, all workstationson the network can also be servers. This a nondedicated serversetup. This approach is used by Sitka and Artisoft, amongothers.The two server approaches have advantages and disadvantages.Nondedicated servers allow for more flexibility, since users canmake resources available on their computers as necessary.However, a nondedicated server approach requires that the usersare willing to take some administrative responsibility for theircomputers and it necessitates that they be somewhat LAN-literate. Backing up the shared data, setting up security, andsetting up access rights become more complicated and oftenbecome the responsibility of the user, not the administrator.Another drawback is that non-dedicated servers often suffersome performance degradation when being used simulta-neously as a workstation and as a server.Dedicated servers have the opposite advantages and disadvan-tages. They are easier to administer since all data is in one place.They are faster because they don’t have a local user to serve. Onthe other hand, it is harder to make resources available on an adhoc basis, since setting up a server is more difficult and time-

consuming. If a dedicated server fails, all users are forced tostop working because all resources are centralized. Your choiceof dedicated or non-dedicated operation will depend on thework your network is doing.

File Service

A file server’s primary task is to make files available to users,although it also makes other resources available, includingprinters and plotters. File service allows users to share the fileson a server. The server PC can make its whole disk, certaindirectories, or certain files available. The file server’s hard diskbecomes an extension of each user’s PC.The NOS can let the LAN administrator determine which usersare allowed to use which files, for example, keeping the mailclerk out of the payroll file. Suppose a user wants to use a fileresiding on the file server’s hard disk. Drive F: is set to corre-spond with the file server’s hard disk. The actual process ofsetting up virtual drives has several names, including mapping,mounting, and publishing.Now, suppose a user wants to run WordPerfect. At the F:prompt, the user types “WP” to load WordPerfect. WordPerfectis loaded from the server over the network, and into the user’sPC’s memory. Meanwhile, other people can use WordPerfectfrom the file server (assuming there is a license for multipleusers). WordPerfect makes sure no other user can get thedocument file being used by “locking” the file. With manyapplications, file locking allows other users to read the docu-ment but not edit it.File service is an extension of the local PC. Applications workjust as they would on a local PC. Some programs, however,have been designed to take advantage of the network, ratherthan just run on one. For example, some databases allow twousers to edit the same table but not the same record and eachuser can see the other’s changes.The NOS provides much more than just file service; it providessecurity, administration, printer sharing, backup, and faulttolerance.

Server OperationThe server software makes a single-user computer into amultiuser machine. Instead of just one user, a server has manyusers. But we must qualify what we mean by “many users.” ANOS allows many users to share the server’s peripherals,printers, disks, and plotters, but it does not allow multipleusers to share its processor. For now let’s see how the file serverallows users to share its peripherals.In many cases, the file server is running the PC’s native operat-ing system (such as DOS or the Macintosh OS) as well as theNOS. When users’ requests come in, the NOS receives andinterprets them, then hands them to the operating system forexecution. So if a request comes in to open a file, DOS opensthe file and gives it to the NOS, which gives it to the user. Ifmany users make requests at the same time, the NOS queuesthem and hands them to DOS one at a time.High-performance NOSs, including Novell NetWare, BanyanVINES, and Microsoft LAN Manager, do not run DOS in thefile server. DOS is replaced with a multitasking operatingsystem, thereby gaining a performance advantage; however, they

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lose some compatibility and require dedicated file servers. InNetWare’s case, it is a proprietary OS. VINES runs Unix; LANManager currently runs OS/2 but eventually will use WindowsNT.

The OS/2 NOSFile service is a tremendous improvement over single-useroperation, it pales in significance to the enhancements that comewith the new NOSs based on multitasking operating systemssuch as IBM/Microsoft OS/2.The biggest advantage of a multitasking operating system is aserver can offer a task. That is, the server can offer its processorto other users while it is serving requests for files and printers.A fast server can be used to do onerous chores like programcompiling, calculations, and database sorting. It also means newtypes of programs can take advantage of the server processor.

SummaryIn this lecture we have seen that Instead of just getting filesfrom the server, the server can run programs that work with theprograms users are running. The best example is a databaseserver. A database server does things like sorting, searching, andindexing so the user’s program and PC don’t have to. This cutsdown on network traffic since fewer items are travelling betweenthe user and server. It also improves security, since all data isstored centrally.

Questions

1. Explain networking Operating System.2. Explain the Advantages of UNIX.3. Explain client and server operations.