Local Area Networks: Software © Abdou Illia, Spring 2007 School of Business Eastern Illinois University (Week 8, Thursday 3/1/2007)

2 Learning Objectives n Identify main functions of operating systems n Describe basic features of common Network operating systems n Explain main features of Network Operating Systems: n Remote Access service n Directory service n Software Disk Fault-tolerance n Clustering n Network Load Balancing

3 Software 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

4 Operating Systems n Program initially loaded into computer memory n Manages hardware & software resources: – Disks, memory, processors, application programs, etc. n Key function: Ensure that each application gets necessary resources n 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

5 Operating Systems n A special program for managing hardware and software resources that ensure each application program gets necessary resources

6 Common OS functions: Multitasking n 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.

7 Common OS functions: Virtual Memory, Security n Virtual memory management: – OS feature that allows loading programs even if RAM is limited – Needs enough HD space n Handling: – Input operations from attached devices (e.g. disks) – Output operations to attached devices (e.g. disks, printers) n Providing resource security – E.g. Directory & files security to provide protection from unscrupulous users

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

9 Network Operating Systems (NOS)

10 Summary 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.

11 Dual-transmission NIC BNC “Thinnet” connector RJ45 connector

12 Ethernet standards

13 Remote Access Service Remote Access Server Remote Access Client Software

14 Remote Access Service n User dials into a remote access server n Server authenticates the user (user must prove identity) n If authenticated, user may use network resources n Client PC needs RAS client software LAN Internal Server RAS Dial-In Client Dial-Up Telephone Line RAS Client Software

15 Directory Service n Needed in large networks with dozens or hundreds of servers n Directory database contains info about all network resources n Usually provides: Single login and Resource lookup. Directory Database

16 Disk Fault-tolerance n Disk Fault-tolerance could be achieved through – Hardware RAID (Redundant Array of Independent Disks) – Software RAID Data spread across these disks Last disk contains ECC* data for disks 1-4

17 Clustering n Technique for providing uninterrupted service (even in case of hardware/software failure) n Combining two or more servers into one virtual server n Services installed on external storage n Users connect to the virtual server ( in illustration) n One of the clustered servers provides the service at a time Mac client Windows client

18 Load Balancing n Load balancing = Distributing the load among multiple servers n No External disk containing services to be provided n Multiple independent servers configured to participate in the load balancing n Same service with the same content on each server n Users connect to the virtual server ( in illustration) n Users’ requests are redirected to one server at a time so that the load is distributed among all the servers Webservice Virtual server

19 Current Network Operating Systems n 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 286Released in 1986, Uses IPX/SPX VersionComment NetWare 3.x – 4.x Included clustering, NDS NetWare 5.x – 6.xSwitch to TCP/IP, Apache webserver Novell Open Enpterprise ServerReleased in 2005, Linux platform

20 Current Network Operating Systems n Microsoft Windows Server Operating Systems – Microsoft Windows NT Server – Microsoft Windows Server 2000: n Windows 2000 Server n Windows 2000 Advanced Server n Windows 2000 DataCenter Server – Microsoft Windows Server 2003 n Windows Server 2003 Standard Edition n Windows Server 2003 Enterprise Edition n Windows Server 2003 DataCenter Edition n Windows Server 2003 Compute Cluster Edition

21 Current Network Operating Systems n 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

22 Current Network Operating Systems n UNIX – Extremely reliable (speed, stability) – UNIX server OS dominate the enterprise server market – Many versions of UNIX exist n UNIX: Must with the Single UNIX Specification n Free UNIX-Like versions initiated by GNU project n Different management utilities

23 Current Network Operating Systems n LINUX – Version of UNIX (Free UNIX-Like) – Runs on Intel PCs; low cost – Available free n 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

24 Current Network Operating Systems n Mac Server OS – "Classic" Mac OS ( ) n User-friendly, completely graphical operating system – Mac OS X Workstation and Server (2001-present) n based on the BSD* implementation of UNIX * Berkeley Software Distribution or Berkeley UNIX Mac OS X versions Date Released Mac OS X v10.0 “Cheetah”March 2001 Mac OS X v10.3 “Panther” October 2003 Mac OS X v10.4 “Tiger”April 2005 Mac OS X v10.5 “Leopard” Upcoming in 2007

25 Summary 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?