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Project Report On

Network Operating System

Strength to Client/Server Architecture

Submitted To Submitted By

Mr. Ashish B.Khare Kavita KarkiAsst. Professor MCA Vth Sem (24)

[Colloquium]

Amrapali Institute of Management and Computer Application

Haldwani

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CONTENT SHEET

(1). Introduction

(1.1). Project Introduction(1.2). Types of Network Operating System(1.3). Why Client/Server Architecture is Important

(2). Evolution

(2.1). First-Generation(2.2). Second-Generation(2.3). Third-Generation

(3).Different Types of NOS

Artisoft's LANtastic

Banyan Vines

Novell's NetWare

Microsoft's LAN Manager

Unix

OS/2

(4).Market Scenario

Novell Netware

Current Netware Situation

(5). Services Provided by NOS

(6).NOS Performance in Client/Server Architecture

(7). Conclusion

(8). Reference

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(1). Introduction:

Client/server architecture is an application design approach that results in the decompositionof an information system into a small number of server functions, executing one ormore hardware platforms, that provides commonly used services to a large number of

client functions, executing on one or more different but interconnected hardwareplatforms.

Client/server is a computational architecture that involves client processes requesting servicefrom server processes Client/server computing is the logical extension of modular

programming. In basic client-server architecture, a personal or centralizedapplication is split into two parts: a client part on a personal platform, and a server

part on a server platform. The terms client and server are used to refer to thehardware platforms and the application software components. Basic client-serverarchitecture are normally organized around a local area network (LAN). The wholeassembly is usually described as a PC-LAN, and consists of many PCs for personal

use (personal platforms), plus one or more shared PCs (server platforms). The localserver platforms on these PC-LANs usually provide gateways into enterprise-wideand external networks, and to the servers on them.

Network Operating System:

A network operating system is a computer operating system that is designed primarily tosupport workstation, personal computer, and in some instance, older terminal thatare connected on a local area network. NOS is an operating system that includesspecial functions for connecting computers and devices into a local area network(LAN) or internetworking. Network Operating Systems (NOS) typically are used to

run computers that act as servers. They provide the capabilities required fornetwork operation.

(1.2). Types Of Network Operating System:

Unlike operating systems, such as Windows that are designed for single users to control onecomputer network operating systems (NOS) coordinate the activities of multiplecomputers across a network. The network operating system acts as a director tokeep the network running smoothly.

The two major types ofnetwork operating systems are:

Peer-to-Peer

Client/Server

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Peer-to-Peer Network Operating System:

Peer-to-peer network operating systems allow users to share resources and files located ontheir computers and to access shared resources found on other computers. However,they do not have a file server or a centralized management source. In a peer-to-peer

network, all computers are considered equal; they all have the same abilities to use theresources available on the network. Peer-to-peer networks are designed primarily forsmall to medium local area networks.

In a wired peer-to-peer network the NOS is installed on every networked computer so thatany networked computer can provide resources and services to all other networkedcomputers. For example, each networked computer can allow other computers to accessits files and use connected printers while it is in use as a workstation. In a wireless peer-to-peer network, each networked device contains a short-range transceiver thatinterfaces with the transceivers of nearby devices or with APs. Like their wiredcounterparts, wireless peer-to-peer networks offer file and resource sharing.

AppleShare and Windows for Workgroups are examples of programs that can function aspeer-to-peer network operating systems.

Fig: peer-to-peer network

Advantages of a peer-to-peer network:

Less initial expense - No need for a dedicated server.

Setup - An operating system (such as Windows XP) already in place may only need to bereconfigured for peer-to-peer operations.

Disadvantages of a peer-to-peer network:Decentralized - No central repository for files and applications.

Security - Does not provide the security available on a client/server network.

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Maintenance is also often more difficult. Because there is no method of centralizedmanagement, there can be many servers to manage (rather than one centralized server), andmany people may have the rights to change the configuration of different server computers. Inthe case of wireless peer-to-peer networks, however, an AP may be one node in the network,allowing users both to share files directly from their hard drives and to access resources from

the servers on the LAN.

2. Client/Server Network Operating System:

Client/server network operating systems allow the network to centralize functions andapplications in one or more dedicated file servers. Individual workstations (clients) haveaccess to the resources available on the file servers. The network operating system providesthe mechanism to integrate all the components of the network and allow multiple users tosimultaneously share the same resources irrespective of physical location. Novell Netwareand Windows 2000 Server are examples of client/server network operating systems.A System software of a local area network (LAN) that integrates the network hardware

components, usually adequate for connecting up to 50 workstations. Controls a network andits message (e.g., packet) traffic and queues, control access by multiple users to networkresources such as files and provides for certain administrative functions, including security.To keep networks running at optimal performance. Network operating system allows large

businesses to function as a single Unix.

Advantages of a client/server network:

Centralized - Resources and data security are controlled through the server.

Scalability - Any or all elements can be replaced individually as needs increase.

Flexibility - New technology can be easily integrated into system.

Interoperability - All components (client/network/server) work together.

Accessibility - Server can be accessed remotely and across multiple platforms.

Disadvantages of a client/server network:

Expense - Requires initial investment in dedicated server.

Maintenance - Large networks will require a staff to ensure efficient operation.

Dependence - When server goes down, operations will cease across the network.

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(1.3): Client-Server Architecture Importance: To understand why Client/Serverarchitecture is so important, let us have a look on some traditional computingarchitectures:

Centralized Multiuser Architecture (Not a Client/Server Architecture):With mainframe

software architecture all intelligence is within the central host computer. Users interactwith the host through a terminal that captures keystrokes and sends that information tothe host. Mainframe software architectures are not tied to the hardware platform. Userinteraction can be done using PCs and UNIX workstations.

This traditional architecture have several advantages such as it is stable, reliable, costeffective for large number of users, single vendor system, etc. But also have severaldisadvantages such as such as its proprietary (incompatible) expensive, license free etc.

File Sharing Architecture (Not Client/Server Architecture): The original PC networkswere based on file sharing architectures, where the server downloads file from the

shared location to the desktop environment. The requested user job then runs in thedesktop environment. This architecture work if shared usage is low, and the volume ofdata to be transferred is low.

Client/Server Architecture: This architecture was developed to overcome limitations of filesharing architecture. In this approach a database server is used to replace file server.Using a relational database management system (RDBMS), User queries could beanswered easily and directly. Network traffic can also be reduced as query response is

provided rather than total file transfer as in file/server architecture.

Fig: Client/Server Architecture

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The basic characteristics of client/server architectures are:

Combination of a client or front-end portion that interacts with the user, and a server or back-end portion that interacts with the shared resource. The client process contains solution-specific logic and provides the interface between the user and the rest of the application

system. The server process acts as a software engine that manages shared resourcessuch as databases, printers, modems, or high-powered processors.

The front-end task and back-end task have fundamentally different requirements forcomputing resources such as processor speeds, memory, disk speeds and capacities, andinput/output devices.

The environment is typically heterogeneous and multi Finder. The hardware platform andoperating system of client and server are not usually the same. Client and server

processes communicate through a well-defined set of standard application programinterfaces (API's) and RPC's.

An important characteristic of client-server systems is scalability. They can be scaledhorizontally or vertically. Horizontal scaling means adding or removing clientworkstations with only a slight performance impact. Vertical scaling means migratingto a larger and faster server machine or multi servers.

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(2). Evolution:

In this section, review networking products that have been through several generations ofsoftware releases to help provide the best examples of the differences seen with differentgenerations of network operating systems. Within various environments, it is not uncommon

to find routers or switches that started life under older, monolithic software and later migratedto more contemporary later generation designs. By reviewing these generations, the positiveeffect on stability and operational efficiency is easy to notice and appreciate.

In general, network operating systems can be traced back to three generations ofdevelopment, each with distinctively different architectural and design goals.

(2.1). First-Generation Network OS: Monolithic Architecture:

Most of the first-generation network operating systems for routers and switches wereproprietary images running in a flat memory space, often directly from flash memory orROM. While supporting multiple processes for protocols, packet handling, and management,they operated using a cooperative, multitasking model in which each process would run tocompletion or until it voluntarily relinquished the CPU.

All of these first-generation network operating systems shared one trait: They eliminatedthe risks of running full-size commercial operating systems on embedded hardware. The

primary goal of these early network operating systems were to operate in a small footprintand to provide speed of operation, while additional features like memory management,

protection, and context switching were either rudimentary or nonexistent. These first-generation network operating systems helped make networking commercially viable andwere deployed on a wide range of products. The downside was that these systems were

plagued with a host of problems associated with resource management and fault isolation;a single runaway process could easily consume the processor or cause the entire system tofail. Such failures were not uncommon in the data networks controlled by older softwareand could be triggered by software errors, rogue traffic, and operator errors.

Legacy platforms of the first generation are still seen in networks worldwide, althoughthey are gradually being pushed into the lowest end of the telecom product lines.

(2.2). Second-Generation Network OS: Control Plane Modularity:

By the mid-1990s, there was a significant increase in the use of data networks worldwide,which quickly challenged the capacity of existing networks and routers. By this time, itwas becoming evident that embedded platforms could actually run full-size commercialoperating systems, at least on high-end hardware, but with one catchthey could notsustain packet forwarding with satisfactory data rates. To help solve this issue, a

breakthrough solution was introduced through implementation of a hard separation between the networking devices control and forwarding planesan approach thatoccurred in the industry's first ASIC-driven routing platform. Forwarding packets entirelyin silicon proved to be viable, clearing the path for next-generation network operatingsystems.

Since second-generation network operating systems were now free from handling packetswitching functions, they were able to focus entirely on control plane functions. Unlike

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their first-generation counterparts, a second-generation OS could now fully use thepotential of multitasking, multithreading, memory management, and context manipulationall making system-wide failures less common. Most core and edge routers installed inthe past few years are running second-generation operating systems, and it is thesesystems that are currently responsible for moving the bulk of traffic on the Internet and in

corporate enterprise networks.

(2.3). Third-Generation Network OS: Flexibility, Scalability, and Continuous

Operation:

Although second-generation designs were very successful, the past 10 years have broughtnew challenges. Organizations are constantly pressured to deliver high-performancenetworks that are flexible, scalable, and reliable, while also lowering operating expenses.Running multiple "best-in-class" operating systems in multiple terabit routers, Layer 2switches, and even security appliances across an organization's network, produced asplintered operational experience where there is no true "network" operating system.

Third-generation network OS are designed to provide a single network operating systemthat is flexible enough to be deployed into multiple types and sizes of network andsecurity devices across an organization's network infrastructure. This single OS must alsoachieve continuous operation, so that software failures in the routing code will not affectthe state of the operational network. Meeting this challenge requires availability andconvergence characteristics that go far beyond the hardware redundancy available insecond-generation routers.

Another key goal of third-generation operating systems is the capability to run with zerodowntime during both planned and unplanned events. Drawing on the lesson learned from

previous designs regarding the difficulty of moving from one OS to another, third-generation operating systems should make the migration path completely transparent tocustomers. They should offer an evolutionary, rather than a revolutionary upgradeexperience typical of the retirement process of legacy software designs.

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(3). Different Types of Network Operating System:

The client process sends a request to the server. The server interprets the message and thenattempts to fulfill the request. In order to fulfill the request, the server may have to referto a knowledge source (database), process data (perform calculations), control a

peripheral, or make an additional request of another server. In much architecture, aclient can make requests of multiple servers and a server can service multiple clients.

The list of network operating systems includes Artisoft's LANtastic, Banyan VINES, Novell'sNetWare and Microsoft's LAN Manager. Some of the main functions of a networkoperating system are printer sharing, common file systems, database sharing,application sharing, managing network name directory and the ability to dohousekeeping for the network's system.

Artisoft's LANtastic:

LANtastic supports a wide variety of PC operating systems like Windows NT 4.0/2000/2003

(Workstation and/or Server), and Windows XP. It comes with an enhanced multi-platformsupport. The installation and operation of the system is fast and user friendly, along with animproved interface that allows all networked PCs to be able to communicate by just using theChat feature. Users are not required to employ a dedicated server or a full-time networkmanager because the system is simple and easy to maintain.

Banyan VINES:

Banyan Virtual Integrated Network Service (VINES) is a network operating system based on proprietary protocol family. The protocol is basically derived from Xerox Network Systems(XNS) protocols, where it uses a client-server architecture that enables clients to requestspecified services like file and printer access from servers.

Novell's NetWare:

This network operating system is a protocol suite designed based on the XNS protocolarchitecture. It provides comprehensive support to most of the desktop operating systems inthe market, including DOS, Windows, Macintosh, OS/2 and UNIX. Novell also supports thelocal area networks and asynchronous wide area communications.

Microsoft's LAN Manager: LAN Manager is anetwork operating system by Microsoft that works as a server application. It runs underMicrosoft OS/2, and was developed in conjunction with 3Com. The file server may

concurrently be used for other tasks like database services. In other words, the systemprovides a good multi-tasking function. It also supports most desktop operating systemslike DOS, Windows and OS/2 clients. Currently, the LAN Manager feature has beensuperseded by Microsoft Windows NT Server and most parts of the LAN Manager are

being used in the Windows NT and Windows 2000.

UNIX: is an operating system that was developed by some of the members of the Multics

team at the bell labs starting in the late 1960's, many of who also helped create the C

programming language. Today, Unix is not just the work of a couple of programmers, many

other organizations, institutes, and various other individuals have contributed significant

additions to Unix and its variants, making it a widely used and popular operating system

today.

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LINUX:

LINUX refers to the family ofUnix-like computeroperating systems using the Linux kernel.

Linux can be installed on a wide variety of computerhardware, ranging from mobile phones,

tablet computers and video game consoles, to mainframes and supercomputers.Linux is the

leading serverOS, accounting for more than 50% of installations and runs the top 10 fastestsupercomputers in the world. Desktop use of Linux has increased in recent years, partly

owing to the popular Ubuntu, Fedora, and openSUSE distributions and the emergence of

netbooks and smartphones running an embedded Linux.

The development of Linux is one of the most prominent examples of free and open sourcesoftware collaboration; typically all the underlying source code can be used, freely modified,and redistributed, both commercially and non-commercially, by anyone under licenses suchas the GNU General Public License. Typically Linux is packaged in a format known as aLinux distribution for desktop and server use. Linux distributions include the Linux kernel

and all of the supporting software required to run a complete system, such as utilities andlibraries, the X Window System, the GNOME and KDE desktop environments, and theApache HTTP Server. Commonly used applications with desktop Linux systems include theMozilla Firefox web-browser, the OpenOffice.org office application suite and the GIMPimage editor.

OS/2:

Jointly developed by Microsoft Corp. and IBM to operate with Intel Corp.'s microprocessors,

OS/2 was originally a 16-bit operating system that was designed to work with 286 processors

and first introduced in 1987. OS/2 later became a graphical interface similar to Windows but

also supported a command line. In fact, many OS/2 and DOS commands are the same.

In 1992, a new 32-bit version was released to operate with 386 and above PCs and at this time

was now solely an IBM product. Later in 1994, IBM released a version it called OS/2 Warp

that included Internet access and additional features. At the same time Microsoft was working

on OS/2 version 3.0; however, it later became Microsoft Windows NT.

OS/2 never became as popular as the other Microsoft operating systems, and softwaredevelopers never created a substantial number of programs to run primarily under OS/2.Although some computer experts say later versions of OS/2 are superior to Windows,

Windows and the number of products created for it still greatly outnumber OS/2 programs.

IBM officially announces on July 14, 2005 that all sales of OS/2 will end on December 23,2005 and that all support from IBM for OS/2 will end on December 16, 2005.

Windows NT:

Windows NT is a family of operating systems produced by Microsoft, the first version ofwhich was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix.It was intended to complement consumer versions of Windows that were based on MS-DOS.

NT was the first fully 32-bit version of Windows, whereas its consumer-orientedcounterparts, Windows 3.1x and Windows 9x, were 16-bit/32-bit hybrids. Windows 2000,

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Windows XP, Windows Server 2003, Windows Vista, Windows Home Server, WindowsServer 2008 and Windows 7 are based on Windows NT, although they are not branded asWindows NT.

A main design goal of NT was hardware and software portability. Various versions of NT

family operating systems have been released for a variety of processor architectures, initiallyIntelIA-32, MIPS R3000/R4000 and Alpha, with PowerPC, Itanium and AMD64 supported

in later releases. The idea was to have a common code base with a custom Hardware

Abstraction Layer(HAL) for each platform.

The table shows a short list of some of the server OSes available today. Most of these are

based on a Unix core.

Server Operating Systems

Operating System CompanyHardware

PlatformNo. of processors Appropriate for:

Windows 2000 Server/Advanced

Server/DatacentreMicrosoft Intel/AMD

4 (Server)8 (Advanced)32 (Datacentre)

Small, medium andlarge servers

Windows Server 2003 R2

Standard/Enterprise/Datacentre/Web

Server/Small Business

Microsoft

Intel/AMD & IA-64, Opteron for 64-bit versions ofWindows Server2003

4 (Standard)Up to 8(Enterprise)Minimum 8,Maximum 64(Datacentre)

Small, medium andlarge servers

Linux (Red Hat, Mandrake, Debian,SuSE, etc.)

Open SourceMany (esp.Intel/AMD)

32 (Linux isreadily used onmore than 4 CPUs)

Small to largeservers

FreeBSD 7.0 Open Sourcex86, Alpha, IA-64,PC-98 andUltraSPARC

4Small to largeservers

Mac OSX Server v10.4 ApplePowerPC with aG3, G4, or G5processor (Apple)

2 (4 availablelater)

Small to mediumservers

NetWare 6.5 Novell Intel/AMD 32Medium to largeservers

Solaris 10 Sun Microsystems Sparc, Intel x64 orx86

128 Medium toenterprise servers

HP-UX 11i v1.6 & HP-UX 11i v2 Hewlett-PackardPA-RISC, IntelItanium

64 Enterprise servers

IRIX 6.5 SGI MIPS 64 Enterprise servers

AIX 5L 5.2 IBMPowerPC(RS/6000)

32 Enterprise servers

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(4). Market Scenario:

Each operating system has its strengths and weaknesses, and its use may depend on your levelof technical competence.

Windows 2000 Professional, Server and Advanced Server can be readily used as small business servers. The strength of Windows lies in the familiarity of the interface; widesupport there is a mass of third party development for the platform, a reasonable price tagand a plentiful supply of available expertise.

The weaknesses of these OSes is the need for user-based licensing. Additionally, significant

maintenance for security resources is required (there is a history of viruses infecting IIS in

particular).

Linux and FreeBSD actually cover a large range of products. The purchase price ranges from

freely downloadable to packaged and supported corporate products costing hundreds of

dollars. Linux, in particular, comes in a huge variety of distributions; some act and look much

like Windows; others can be used to build an appliance server (see below) that are totally

administered through a Web or other interfaces. The core, or Kernel, of the operating systems

are the same, however (although there may be variations in the version of the kernel used in a

given distribution).

Mac OS X shares origins with FreeBSD, and has many of the same features and stability. The

interface is very Macintosh, and you need to buy Apple hardware to use it. There aren't many

third party applications for it as yet. It comes with an unlimited user license.

In contrast to Mac OS X, Novell NetWare 6 is a very mature server OS. It was long sidelinedas purely a 'file and print server', and missed out on picking up on a lot of the application

server business. It still makes a very capable workgroup or enterprise server. Its file and Web

services are first-rate, and it has a wide range of management interfaces, including a Web

interface. Unfortunately, there are few third-party applications for it, installation is quite

technical and it's not cheap.

NetWare is a network operating system developed by Novell, Inc. It initially used

cooperative multitasking to run various services on a personal computer, with network

protocols based on the archetypal XeroxNetwork Systemsstack. Novell superseded NetWare

with Open Enterprise Server(OES) from 2005. The latest version of NetWare is v6.5 SupportPack 8, which is identical to OES 2 SP1, NetWare Kernel.

NetWare provides transparent remote file access and numerous other distributed networkservices, including printer sharing and support for various applications such as electronic mailtransfer and database access. NetWare specifies the upper five layers of the OSI referencemodel and, and runs on any media-access protocol (Layer 2). In addition, NetWare runs onvirtually any kind of computer system, from PCs to mainframes. NetWare and its supporting

protocols often coexist on the same physical channel with many other popular protocols,including TCP/IP and AppleTalk .

Novell NetWare, introduced in the early 1980s based on Xerox Network Systems (XNS), is based on a client-server architecture. Clients (sometimes called workstations) request

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services, such as file and printer access, from servers. NetWare's client/server architecturesupports remote access that is transparent to users through remote procedure calls. A remote

procedure call begins when the local computer program running on the client sends aprocedure call to the remote server. The server then executes the remote procedure call andreturns the requested information to the local client.

The most popular protocols in the Novell NetWare suite are:

IPX: Internetwork Packet Exchange protocol- Routing and networking protocol at layer 3.

When a device to be communicated with is located on a different network, IPX routes the

information to the destination through any intermediate networks . IPX is similar to IP

(Internet Protocol) in the TCP/IP suite.

SPX: Sequenced Packet Exchange protocol - Control protocol at the transport layer (layer 3)

for reliable, connection-oriented datagram transmission. SPX is similar to TCP in the TCP/IP

suite.

NCP:Network Core Protocol is a series of server routines designed to satisfy applicationrequests coming from, for example, the NetWare shell. Services provided by NCP include fileaccess, printer access, name management, accounting, security, and file synchronization.

NetBIOS: Network Basic Input/output System(NetBIOS) session-layer interfacespecification from IBM and Microsoft. NetWare's NetBIOS emulation software allows

programs written to the industry-standard NetBIOS interface to run within the NetWaresystem .

NetWare application-layer services:NetWare Message Handling Service(NetWare MHS),Btrieve, NetWare Loadable Modules (NLMs), and various IBM connectivity features.

NetWare MHS is a message delivery system that provides electronic mail transport. Btrieve is Novell's implementation of the binary tree database access mechanism. NLMs areimplemented as add-on modules that attach into the NetWare system. NLMs for alternate

protocol stacks, communication services, database services, and many other services arecurrently available from Novell and third parties.

Since the NetWare 5.0 (the current version of NetWare is 6.5), all Novell network servicescan be run on top of TCP/IP. There, IPS and SPX became Novell legacy network andtransport layer protocols.

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Current NetWare situation:

As of 2010 some organizations still use Novell NetWare, but its ongoing decline in popularitybegan in the mid-1990s. Modern (2009) NetWare and OES installations are used by largerorganizations that may need the added flexibility they provide.

Microsoft successfully shifted market share away from NetWare products toward their own inthe late-1990s. Microsoft's more aggressive marketing was aimed directly to managementthrough major magazines; Novell NetWare's was through IT specialist magazines withdistribution limited to select IT personnel.

Novell did not adapt their pricing structure accordingly and NetWare sales suffered at thehands of those corporate decision makers whose valuation was based on initial licensing fees.As a result organizations that still use NetWare, eDirectory, and Novell software often have ahybrid infrastructure of NetWare, Linux, and Windows servers.

NetWare dominated the network operating system (NOS) market from the mid-80s throughthe mid- to late-90s due to its extremely high performance relative to other NOS technologies.Most benchmarks during this period demonstrated a 5:1 to 10:1 performance advantage over

products from Microsoft, Banyan, and others.

Many quantitative studies of free / open source software focus on topics including marketshare and reliability, with numerous studies specifically examining Linux. The Linux marketis growing rapidly, and the revenue of servers, desktops, and packaged software runningLinux was expected to exceed $35.7 billion by 2008.

IDCs Q1 2007 report indicated that Linux held 12.7% of the overall server market at thattime. This estimate was based on the number of Linux servers sold by various companies anddid not include server hardware purchased separately and had Linux installed on it later. InSeptember 2008 Microsoft CEO Steve Ballmeradmitted that 60% of web-servers run Linuxversus 40% that run Windows Server.

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Fig: OS Shipments With PC Systems Worldwide Market Share

The Microsoft Disk Operating System (DOS) and the windowing system that runs on top ofit, Microsoft Windows 3.x, are very nearly ubiquitous in the PC environment. Almost everyPC ever made has been bundled with some flavor of DOS (including some compatible non-Microsoft versions such as products from IBM and Digital Research). Since the introductionof Microsoft Windows 3.0, almost all PCs are also bundled with Windows. Windows 9x andWindows NT have replaced DOS and Windows 3.x see Figure in recent years in bundles

with new machines.

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(5). Services Provided by Network Operating System:

The NOS is the "brain" of the entire network, acting as the command center and enabling thenetwork hardware and software to function as one cohesive system.

In a client-server network the NOS runs on a computer called the network server. The servermust be a specific type of computer. For example, the most commonly used client-serverversion of the NetWare NOS runs on Intel-based computers.

The client part of a client-server network is any other network device or process that makesrequests to use server resources and services. For example, network users at workstationsrequest the use of services and resources though client software, which runs in theworkstation and communicates with the NOS in the server by means of a common protocol.

Fig: Services Provided by NOS in Client Site.

"Resources" generally refers to physical devices that an application may need to access:hardware such as hard disks, random access memory (RAM), printers, and modems. The

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network file system is also a server resource. The NOS manages access to all these serverresources.

A client-server NOS is responsible for coordinating the use of all resources and servicesavailable from the server on which it is running. NOSis generally reserved for software thatenhances a basic operating system by adding networking features.

A server-based network operating system provides networking support for multiplesimultaneous users, each with the ability to access network resources, as well as security andother administrative functions.

Fig: Services Provided by NOS in Server Site.

The NOS also provides many "services," which are tasks performed or offered by a serversuch as coordinating file access and file sharing (including file and record locking), managingserver memory, managing data security, scheduling tasks for processing, coordinating printeraccess, and managing internetwork communications.

Among the most important functions performed by a client-server NOS are ensuring thereliability of data stored on the server and managing server security.

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Network Operating System Functions are defined below.

(5.1). File and print sharing:File sharing involves setting up a common storage point for a

company's documents - a network drive, as it were. Print sharing allows multiple computersto use a single printer. Windows 95, 98 and ME do have file and print sharing, but are notrecommended for use as server OSes.

(5.2). Web site services:A hypertext transfer protocol (HTTP) server is included with manyserver OSes, either via an integrated application, or other HTTP applications such as theApache open source server. Some OSes also come with more advanced features, such asdatabase integration (so you can dynamically build Web pages based on information in adatabase), personalization and scripting. The world's most popular HTTP server application,Apache, comes with just about every version of UNIX and also runs on Windows. Microsoft

provides Internet Information Server (IIS) for Windows platforms.

(5.3). Account administration for users: User management and support for Logon andLogoff.

(5.4). Security: Security features such as authentication, authorization, logon restriction andaccess control. On a NetWare client-server network, you "log on" to the network server fromthe workstation. To log on, you provide your user name and passwordalso known as a login

to the server. If your user name and password are valid, the server authenticates you andallows you access to all network services and resources to which you have been grantedrights. As long as you have proper network rights, the client-server NOS provides the services

or resources requested by the applications running on your workstation.

(5.5). Installed Components:

Client functionality

Server functionality

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(6). Network Operating System Performance in Client/Server Architecture:

A network operating system (NOS) is a computer operating system that is designed fornetworkuse.

Usually a NOS is a complete operating system with file, task and job management. However,with some earlier operating systems, it was a separate component that enhanced a basic non-networking operating system by adding networking capabilities. Examples include Novell's

Netware and Artisoft's LANtastic.

A variation on the client-server network is the server-based network or thin client-servernetwork. This kind of network also consists of servers and clients, but the relationship

between client and server is different. Thin clients are similar to terminals connected tomainframes: the bulk of the processing is performed by the server and the client presents theinterface. Unlike mainframe terminals, however, thin clients are connected to a network, notdirectly to the server, which means the client does not have to be physically near the server.

The term "thin client" usually refers to a specialized PC that possesses little computing powerand is optimized for network connections. Windows-based terminal (WBT) and networkcomputer (NC) are two terms often used interchangeably with thin client. These machines areusually devoid of floppy drives, expansion slots, and hard disks; consequently, the "box" orcentral processing unit is much smaller than that of a conventional PC.

The "thin" in thin client refers both to the client's reduced processing capabilities and to theamount of traffic generated between client and server. In a typical thin-client environment,only the keystrokes, mouse movements, and screen updates travel across the connection. (Theterm "thin" is also used generically to describe any computing process or component that usesminimal resources.)

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Fig: Thin clients range from complete dependence on the server to the autonomous PC,

which can both run on its own applications and act as a terminal.

Figure shows where clients fall on the "thinness" continuum: mainframe terminals are thethinnest of all, followed by thin clients and conventional PCs. Thin clients are "fatter" thanmainframe terminals because they run some software locally a scaled-back operating system,a browser, and a network client but they do not store files or run any other applications. PCs,

on the other hand, can either be fully autonomousrunning all applications and storing allfiles locally or they can run browser or terminal-emulation software to function as thin clients.

Unlike mainframe terminals, which show text-only, platform-specific screens, thin clientsdisplay the familiar Windows desktop and icons. Furthermore, the Windows display remainsconsistent even when using non-Windows applications, so you do not have to learn newinterfaces in heterogeneous network environments.

Server-based computing usually involves "server farms," which are groups of interconnectedservers that function as one. Thin clients link to the farm instead of a particular server. If asingle server fails, the other servers in the farm automatically take over the functions of the

failed server so that work is not interrupted and data is not lost.

The two primary protocols for thin-client computing are remote display protocol (RDP) andindependent computing architecture (ICA). RDP was developed by Microsoft for its TerminalServer and ICA is Citrix technology. Both protocols separate the application logic from theuser interface; that is, they pick out the part of the application that interacts with you such askeyboard and mouse input and screens. Only the user interface is sent to the client, leaving therest of the application to run on the server. This method drastically reduces network trafficand client hardware requirements. ICA clients, for example, can have processors as slow as anIntel 286 and connection speeds as low as 14.4 kilobits per second (Kbps).

Although RDP is the older protocol, ICA has become the de facto standard for server-basedcomputing. ICA presents some distinct advantages over RDP, not the least of which is ICA's

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platform independence. ICA transmits the user interface over all standard networkingprotocolsTCP/IP, IPX, SPX, PPP, NetBEUI, and NetBIOSwhereas RDP supports onlyTCP/IP. ICA also supports all standard clients from Windows to UNIX to Macintosh, butRDP can be used only with Windows 3.11 and later. Furthermore, RDP is a streaming

protocol that continuously uses bandwidth while the client is connected, whereas ICA sends

packets over the network only when the mouse or keyboard is in use. As a result, mostnetwork administrators run ICA on top of RDP to obtain the best functionality.

Server-based computing is best used in environments where only a few applications areneeded or when many people will be using the same machine, such as in shift work. Forexample, if you use only a spreadsheet, a word processor, and e-mail, a thin client may be anideal solution. Likewise, if the applications rely on databases and directories that are alreadyserver-based, such as with airline reservations or patient charts, thin-client computing might

be a good choice. Networks with many different platforms can also benefit from server-basedcomputing: you can directly access UNIX, Macintosh, mainframe, or other non-Windowsapplications via ICA without the mediation of cumbersome translation applications. If,

however, you need to use high-end applications such as desktop publishing, graphics, orcomputer-aided design, the conventional PC with its local computing power provides the onlyviable option.

Thin-client computing has several other advantages. Because of their simplicity, thin clientsare easier for an IT staff to maintain: users cannot tamper with the settings or introduceflawed or virus-infected software into the system. The server-centric model also allowsupgrades to be performed at the server level instead of the client level, which is much lesstime consuming and costly than updating individual PCs. Thin clients typically do not

become obsolete as quickly as their fatter counterpartsthe servers will, but they are fewer innumber and therefore easier to upgrade or replace. Furthermore, thin clients are less likely to

be stolen: because they cannot function without a server, they are useless in a homeenvironment.

Disadvantages of thin clients include reduced computing power, which makes them practicalonly in limited circumstances, and absolute reliance on the network. With conventional PCsusers can run applications locally, so when the network goes down, they do not necessarilyexperience work stoppage. On the other hand, the slightest power outage can cripple a thin-client network for long time: after power is restored, all the clients request the initial kernelfrom the server at the same time. Also, it is difficult if not impossible to customize a thinclient. If you need to install a scanner or other peripheral device, a thin client cannot

accommodate it (printers are supported). Furthermore, you cannot customize the look and feelof your desktop, which for some may be disheartening or frustrating.

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