Local Area Networks: Software

© Abdou Illia, Spring 2007

School of BusinessEastern Illinois University

(Week 8, Thursday 3/1/2007)

2Learning Objectives

Identify main functions of operating systems

Describe basic features of common Network operating systems

Explain main features of Network Operating Systems: Remote Access service Directory service Software Disk Fault-tolerance Clustering Network Load Balancing

3Software and Support Systems

- Workstation Operating System- Client application programs

- Network Operating System-Utility programs- Application programs:

- Word processor- Spreadsheets- Accounting

• Workstation Operating System on workstations• Network Operating System on servers

4Operating Systems

Program initially loaded into computer memory

Manages hardware & software resources:– Disks, memory, processors, application programs, etc.

Key function: Ensure that each application gets necessary resources

Suppose that a Web browser and a word processor are executed at the same time. Which resources the two applications might need to access to ?

User

Application program

Operating system

Hardware

Interfaces

5Operating Systems

A special program for managing hardware and software resources that ensure each application program gets necessary resources

6Common OS functions: Multitasking

Multi-tasking (multiple prog./tasks running at the same time)– OS allocates small amount of the time to each prog./task– Jumps quickly from one prog./task to another.

7Common OS functions: Virtual Memory,Security Virtual memory management:

– OS feature that allows loading programs even if RAM is limited– Needs enough HD space

Handling:– Input operations from attached devices (e.g. disks)– Output operations to attached devices (e.g. disks, printers)

Providing resource security– E.g. Directory & files security to provide protection from

unscrupulous users

8Network Operating Systems (NOS)

OS designed for Servers use (also called SOS)Same functions as Workstation OS

+

- Ability to manage users and other resources common to the LAN

- Providing key network services

Common resources managed by NOS– Server(s)– Printer(s)– Network interconnection(s) – Users– Group policies to be applied to users and computers

9Network Operating Systems (NOS)

10Summary Questions

Your organization has 12 employees, each with his or her own stand-alone PC running Windows 98. Each computer has a 10 Mbps NIC that could work with coaxial cable or twisted pair (see next slide)

a) List all the additional hardware and software you would have to buy to install a 100BaseTX LAN. Be very sure that you list all the things the organization will have to buy. The organization wishes to use electronic mail, word processing, file sharing, and print sharing with four existing printers fed with parallel ports.

b) How many ports should the hub or switch have? Explain.

11Dual-transmission NIC

BNC “Thinnet” connector

RJ45 connector

12Ethernet standards

13Remote Access Service

Remote Access ServerRemote Access Server

Remote Access Client

Software

14Remote Access Service

User dials into a remote access server

Server authenticates the user (user must prove identity)

If authenticated, user may use network resources

Client PC needs RAS client software

LAN

InternalServer

RAS

Dial-InClient

Dial-UpTelephone

Line

RASClient

Software

15Directory Service

Needed in large networks with dozens or hundreds of servers

Directory database contains info about all network resources

Usually provides: Single login and Resource lookup.

Directory Database

16Disk Fault-tolerance

Disk Fault-tolerance could be achieved through– Hardware RAID (Redundant Array of Independent Disks)– Software RAID

File

Data spread across these disks

Last disk contains ECC* data for

disks 1-4

17Clustering Technique for providing uninterrupted service (even in case of

hardware/software failure)

Combining two or more servers into one virtual server

Services installed on external storage

Users connect to the virtual server (167.10.11.5 in illustration)

One of the clustered servers provides the service at a time

Server Server

HubHub

Virtual server167.10.11.5

SharedFolder- Web service- Email service

Win 2000 Pro WorkstationWin 98 Workstation

External Disk

Mac client Windows client

18Load Balancing

Hub

Load balancing = Distributing the load among multiple servers

No External disk containing services to be provided

Multiple independent servers configured to participate in the load balancing

Same service with the same content on each server

Users connect to the virtual server (167.10.11.5 in illustration)

Users’ requests are redirected to one server at a time so that the load is distributed among all the servers

Server

Webservice

Server

Webservice

Server

Webservice

Server

Webservice

Server

Webservice

Virtual server167.10.11.5

19Current Network Operating Systems

Novell NetWare SOS– Once dominant, but market share has shrunk

– Excellent file service

– Excellent directory service called NetWare Directory Services (NDS), now eDirectory.

NetWare strong directory service is convincing many medium firms to continue using NetWare.

NetWare 286 Released in 1986, Uses IPX/SPXVersion Comment

NetWare 3.x – 4.x Included clustering, NDSNetWare 5.x – 6.x Switch to TCP/IP, Apache webserver

Novell Open Enpterprise Server Released in 2005, Linux platform

20Current Network Operating Systems

Microsoft Windows Server Operating Systems– Microsoft Windows NT Server

– Microsoft Windows Server 2000: Windows 2000 Server Windows 2000 Advanced Server Windows 2000 DataCenter Server

– Microsoft Windows Server 2003 Windows Server 2003 Standard Edition Windows Server 2003 Enterprise Edition Windows Server 2003 DataCenter Edition Windows Server 2003 Compute Cluster Edition

21Current Network Operating Systems

Microsoft Windows Server Operating Systems– Easy to install, learn, and use because resembles

desktop Windows

– Is dominant for small business and small department servers

– Windows Server OS has serious reliability problems:

– Tend to crash more frequently than other OS

– Windows 2003 Server versions promise to improve reliability, but:

– A path called Windows Server 2003 R2 released in 2005

22Current Network Operating Systems

UNIX– Extremely reliable (speed, stability)

– UNIX server OS dominate the enterprise server market

– Many versions of UNIX exist UNIX: Must with the Single UNIX Specification Free UNIX-Like versions initiated by GNU project Different management utilities

23Current Network Operating Systems

LINUX– Version of UNIX (Free UNIX-Like)– Runs on Intel PCs; low cost– Available free

But usually pay around $50 to $150 for packaged version

– Reliable like other UNIX versions– Open Source: Many people are developing tools to add

to the LINUX core

24Current Network Operating Systems

Mac Server OS– "Classic" Mac OS (1984-2001)

User-friendly, completely graphical operating system – Mac OS X Workstation and Server (2001-present)

based on the BSD* implementation of UNIX

* Berkeley Software Distribution or Berkeley UNIX

Mac OS X versions Date ReleasedMac OS X v10.0 “Cheetah” March 2001Mac OS X v10.3 “Panther” October 2003Mac OS X v10.4 “Tiger” April 2005

Mac OS X v10.5 “Leopard” Upcoming in 2007

25Summary Questions

1. In remote access service, what kind of software does the remote PC need? What is needed on the LAN side?

2. What kind of services are provided by Directory servers? What is disk fault-tolerance? What is the difference between Clustering and Network Load Balancing?

3. What is the difference between a Workstation Operating System and a Network Operating System?

4. Name two Workstation Operating System and two NOS.

5. Name one important strength of Novell NetWare NOS that is convincing many firm to continue using it.

6. What is virtual memory?