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CS-

COMPUTER

NETWORKING

Table of Contents

• CHAPTER 1: INTRODUCTION TO NETWORKING..............1-
• 1.1 What is a Network?..................................................................................1-
• 1.2 Basic Components of Network.................................................................1-
  • 1.2.1 Terminal.........................................................................................1-
  • 1.2.2 Workstation....................................................................................1-
  • 1.2.3 Server.............................................................................................1-
  • 1.2.4 Network Interface Card..................................................................1-
  • 1.2.5 Communication Media...................................................................1-
• 1.3 Exercises...................................................................................................1-
• CHAPTER 2: COMMUNICATION MEDIA...............................2-
• 2.1 What is Communication...........................................................................2-
  • 2.1.1 Unshielded Twisted (UTP) Cable..................................................2-
  • 2.1.2 Shielded Twisted (STP).................................................................2-
• 2.2 Fiber Optic................................................................................................2-
  • 2.2.1 Advantages of Fiber Optic.............................................................2-
  • 2.2.2 Disadvantages of Fiber Optic.........................................................2-
• 2.3 Unguided Transmission Media.................................................................2-
  • 2.3.1 Terrestrial Microwave....................................................................2-
  • 2.3.2 Microwave Transmission...............................................................2-
  • 2.3.3 Satellite Communication................................................................2-
  • 2.3.4 Infrared Transmission....................................................................2-
• 2.4 Transmission Impairments.......................................................................2-
• 2.5 Review Questions.....................................................................................2-
• CHAPTER 3: NETWORK TOPOLOGIES.................................3-
• 3.1 What is a Topology?.................................................................................3-
• 3.2 Bus Topology...........................................................................................3-
  • 3.2.1 How a Bus Network Works...........................................................3-
  • 3.2.2 Advantages of Bus.........................................................................3-
  • 3.2.3 Disadvantages of Bus.....................................................................3-
• 3.3 Star Topology...........................................................................................3-
  • 3.3.1 How a Star Network Works...........................................................3-
  • 3.3.2 Advantages of the Star...................................................................3-
  • 3.3.3 Disadvantages of Star.....................................................................3-
• 3.4 Ring Topology..........................................................................................3-
  • 3.4.1 How a Ring Network Works..........................................................3-
  • 3.4.2 Advantages of Ring........................................................................3-
  • 3.4.3 Disadvantages of Ring...................................................................3-
• 3.5 Mesh Topology.........................................................................................3-
  • 3.5.1 Advantages of Mesh.......................................................................3- CN110 TABLE OF CONTENTS
  • 3.5.2 Disadvantages of Mesh..................................................................3-
• 3.6 Variations of the Major Topologies..........................................................3-
  • 3.6.1 Hybrid Star.....................................................................................3-
  • 3.6.2 Star Bus..........................................................................................3-
  • 3.6.3 Star Bus Topology.........................................................................3-
  • 3.6.4 Hybrid Topologies.........................................................................3-
• 3.7 Medium Access Control Techniques for Bus and Ring Topology...........3-
  • 3.7.1 CSMA/CD......................................................................................3-
  • 3.7.2 Token Bus....................................................................................3-
  • 3.7.3 Token Ring...................................................................................3-
  • 3.7.4 Features of Token Passing Mechanism........................................3-
• 3.8 Review Questions...................................................................................3-
• DEVICES..........................................................................................4- CHAPTER 4: NETWORKING AND INTERNETWORKING
• 4.1 Introduction..............................................................................................4-
  • 4.1.1 Networking Devices.......................................................................4-
  • 4.1.2 Internetworking Devices................................................................4-
  • 4.1.3 Hub.................................................................................................4-
  • 4.1.4 Repeater.........................................................................................4-
  • 4.1.5 Strengths and Limitations of Repeaters.........................................4-
• 4.2 Bridge.......................................................................................................4-
  • 4.2.1 Types of Bridges............................................................................4-
  • 4.2.2 Strengths and Limitations of Bridges.............................................4-
  • 4.2.3 Router.............................................................................................4-
  • 4.2.4 Routing Table...............................................................................4-
  • 4.2.5 Strengths and Limitations of Routers...........................................4-
• 4.3 Brouters..................................................................................................4-
• 4.4 Gateway..................................................................................................4-
  • 4.4.1 Strengths and Limitations of Gateway.........................................4-
• 4.5 Review Questions...................................................................................4-
• CHAPTER 5: TYPES OF NETWORKING.................................5-
• 5.1 Network Types.........................................................................................5-
  • 5.1.1 Peer-To-Peer Network...................................................................5-
  • 5.1.2 Server-Based Network...................................................................5-
• 5.2 Categories of the Networks......................................................................5-
  • 5.2.1 Local Area Network.......................................................................5-
  • 5.2.2 Metropolitan Area Network...........................................................5-
  • 5.2.3 Wide Area Network.......................................................................5-
  • 5.2.4 Internetworks.................................................................................5-
• 5.3 Exercises...................................................................................................5- CN110 TABLE OF CONTENTS
• FORMAT..........................................................................................6- CHAPTER 6: COMMUNICATION PROTOCOLS & DATA
• 6.1 Introduction..............................................................................................6-
• 6.2 Analog and Digital Signals.......................................................................6-
  • 6.2.1 Information....................................................................................6-
• 6.3 Switching Techniques...............................................................................6-
  • 6.3.1 Circuit Switching...........................................................................6-
  • 6.3.2 Packet Switching............................................................................6-
  • 6.3.3 Message Switching........................................................................6-
• 6.4 Network Communication and Data Packets.............................................6-
  • 6.4.1 Packet Structure.............................................................................6-
• 6.5 Data Transmission and Access Method....................................................6-
  • 6.5.1 Contention......................................................................................6-
  • 6.5.2 Token Passing..............................................................................6-
  • 6.5.3 Demand Priority...........................................................................6-
  • 6.5.4 Polling..........................................................................................6-
• 6.6 Multiplexing...........................................................................................6-
  • 6.6.1 Frequency Division Multiplexing................................................6-
  • 6.6.2 Time Division Multiplexing.........................................................6-
  • 6.6.3 Synchronous TDM.......................................................................6-
• CHAPTER 7: OSI MODEL AND PROTOCOLS........................7-
• 7.1 Introduction..............................................................................................7-
• 7.2 OSI Reference Model...............................................................................7-
  • 7.2.1 Layered Architecture of OSI..........................................................7-
  • 7.2.2 Function Each Layer......................................................................7-
  • 7.2.3 Some Popular Communications Architectures..............................7-
  • 7.2.4 Comparison between OSI and TCP/IP Model...............................7-
• 7.3 Review Questions...................................................................................7-
• CHAPTER 8: NETWORK SECURITY.......................................8-
• 8.1 Security.....................................................................................................8-
• 8.2 Threat Classification.................................................................................8-
• 8.3 Network Security Techniques..................................................................8-
  • 8.3.1 Access Control Techniques............................................................8-
  • 8.3.2 Password........................................................................................8-
  • 8.3.3 Dial Back .......................................................................................8-
  • 8.3.4 Biometric Techniques....................................................................8-
  • 8.3.5 Encryption Techniques..................................................................8-
  • 8.3.6 Encryption Methods.......................................................................8-

CHAPTER 1: INTRODUCTION TO

NETWORKING

Chapter Objectives:

At the completion of this chapter, students should have learned:  The basic concepts of networking; How the computers are connected together and communicate with each other; How it can be advantageous to a company; What are the disadvantages of networking:

Contents:

 What is a network?  Basic components of network  Terminal  Workstation  Server  Network interface card  Communication media  Network operating system  Peripheral devices  Advantages and disadvantages of networking  Advantages and disadvantages of networking  Exercises

CS163 CHAPTER 1: INTRODUCTION TO NETWORKING

1. Dumb Terminals Dumb terminals are those which have limited functions and are driven with information from a host computer. Normally, they consist of a Cathode Ray Tube (CRT) display screen with a full alphanumeric keyboard and can be connected directly to a computer system (host computer) through some sort of communications interface. In most cases, data is transmitted directly through the communication interface as it is typed on the keyboard. 2. Intelligent Terminals The category of intelligent or programmable terminals is probably the largest and widest ranging group. Unlike dumb terminals, intelligent terminals are equipped with a processor that can support an instruction set to direct the basic functions of the terminal. Like any other type of computer that has a processor, these terminals normally have additional memory and storage devices such as disc drives. Intelligent terminal are, therefore, capable of stand-alone processing and can support a variety of software applications which, in turn, enable them to support a variety of communications interfaces through the use of emulation program. This is also means that, unlike dumb terminals, intelligent terminals are able to use addresses and sophisticated access method to transmit and receive messages. 3. Graphic Terminals Graphic terminals are display devices that provide a means not only for displaying data in graphical form, but also for manipulating and modifying the data presented. Generally, graphic terminal keyboards have a number of specific or programmable function keys in addition to the full alphanumeric keys of a normal keyboard and the resolution of the display screen is normally a lot higher to enable more detailed displays 1.2.2 Workstation A workstation is a client. More specifically, it is a standalone computer equipped with it’s own processor and system and application software. It can perform its functions independent of the network. To expand its resources and knowledge, it may get connected to a network. Workstation

CS163 CHAPTER 1: INTRODUCTION TO NETWORKING 1.2.3 Server Network plays one of two basic roles at any given moment, the computer is either acting s a client or as a server. A server is a computer that shares its Resources across the network, and a client are one that accesses shared resources. Depending on the size and requirements of the network, servers can be classified as below:

1. File Server A file server allows user to share files. It several LAN users need access to an application such as word processing, only one copy of the application software needs to reside on a file server. This copy can be shared among all the users. When a user requests to start an application, that application is downloaded into the users workstation. Consider the saving in disk space in a company having 100 users for application package that requires 10 MB of disk storage. Storage on the file server requires only 10 MB of disk space for all users. Storing the same application on 100 users’ local disk drives will require 1, MB of disk space. This is only an example of one application. Same logic can be applied when hundreds of different application programs needed. 2. Database Server The database server was developed to solve the problem of passing an entire file over the medium. The most common example of a database server is the SQL server. Structured Query Language (SQL) is standard database definition, access, and update language for relational database. An SQL server accepts a database request, accesses all necessary records locally, and then sends only the result back to the requester (not the whole database). 3. Print Server Print server allows anyone on the network to have access to a printing service. 4. Disk Server It is server with large storage. A portion of storage is given to each user to store their files/data. It is very useful in university where each student is given a user account with password and some storage space in disk server. Once the student completes the education the same space can be assigned to new student. 5. Dedicated Vs Non-Dedicated Server Many networks will let their user run standard programs while their computer is simultaneously functioning as a server to others. A computer that both runs standard programs and lets other user see its data at the same time is said to be “non-dedicated server”. Non- dedicated servers can be clever way of setting up a small LAN without having to buy any extra system. Dedicated server are specially

CS163 CHAPTER 1: INTRODUCTION TO NETWORKING  Increased administrative overheads  Increased dependency

1.3 Exercises

 List and describe the basic components of a network with their function.  List the functions of NIC.  Distinguish between dedicated and non-dedicated server.  List and describe the advantages and disadvantages of networking.  List different types of server and their purpose.

CHAPTER 2: COMMUNICATION MEDIA

Chapter Objectives:

To make a network, all the computers and resources (studied in first chapter) have to be linked with each other. At the completion of this chapter, students should have learned:  Different types of wireless and non-wireless communication media;  Their advantages and disadvantages;  Comparison of these media in terms of cost effectiveness, durability and distance covered;  Scenarios discussions to choose appropriate media for different purposes;

Contents:

 What is communication?  Types of communication  Guided communication media  Twisted  Coaxial cable  Fiber optic  Unguided communication  Infrared  Microwave  Satellite  Transmission Impairments  Attenuation  Noise  Exercise

CS163 CHAPTER 2: COMMUNICATION MEDIA Category 1 : Applies to transmit traditional UTP telephones cabling, which is designed to carry voice but not data. Category 2 : Certifies UTP cabling for bandwidth up to 4 Mbps and consists of four pair of wires. Since 4 Mbps is slower than most networking technologies in the use today. Category 2 is rarely encountered in networking environment. Category 3 : Certifies UTP cabling for bandwidth up to 10Mbps. This includes most conventional networking technologies, such as 10BaseT Ethernet and 4Mbps token ring etc. Category 3 consists of four pairs, each having minimum 3 twist per foot. Category 4 : Certifies UTP cabling for bandwidth up to 10Mbps. This includes primarily 10BaseT Ethernet and 16Mbps token ring. Category 4 consists of four pairs. Category5 : Used for data transmission up to 100Mbps Category 5 also consists of four pairs. UTP is particularly prone to cross talk, and the shielding included with STP is designed specifically to reduce this problem. 2.1.2 Shielded Twisted (STP) STP includes shielding to reduce cross talk as well as to limit the effects of external interference. For most STP cables, this means that the wiring includes a wire braid inside the cladding or sheath material as well as a foil wrap around each individual wire. This shield improves the cable's transmission and interference characteristics, which, in tern, support higher bandwidth over longer distance than UTP. Coaxial Cable : Coaxial cable, commonly called coax, has two conductors that share the same axis. A solid copper wire runs down the center of the cable, and this wire is surrounded by plastic foam insulation. The foam is surrounded by a second conductor, wire mesh tube, metallic foil, or both. The wire mesh protects the wire from EMI. It is often called the shield. A tough plastic jacket forms the cover of the cable, providing protection and insulation. Where Ethernet is concerned, there are two types of coaxial cable, called this Ethernet (also known as thinnet or thinwire,) and thick Ethernet (also known as thinnet or thickwire). The Institute of Electrical and Electronics Engineers (IEEE) designates these cable types as 10Base2 and 10Base5, respectively, where these notations indicates: Total bandwidth for the technology: in this case, 10 means 10Mbps Base: indicates that the network uses baseband signaling and this applies to both types of cable. 2 or 5: a rough indicator of maximum segment length, measured in hundreds of meters; thinwire support a maximum segment length of 185 meters, which rounds up to 200; thickwire supports a maximum segment length of 500 meter

CS163 CHAPTER 2: COMMUNICATION MEDIA Fiber Optic Cable : fiber optic cable transmits light signals rather than electrical signals. It is enormously more efficient than the other network transmission media. As soon as it comes down in price (both in terms of the cable and installation cost), fiber optic will be the choice for network cabling. A light pulse can be used to signal a ‘1’ bit; the absence of a pulse signals a ‘0’ bit. Visible light has a frequency of about 108 MHz, so the bandwidth of an optical transmission system is potentially enormous. An optical transmission system has three components: the transmission medium, the light source and the detector. The transmission medium is an ultra-thin fiber of glass or fused silica. The light source is either a LED (Light Emit Diode) or a laser diode, both of which emits light pulses when a electrical current is applied. The detector is a photo diode, which generates an electrical pulse when light falls on it. Silica tube

2.2 Fiber Optic

A cable may contain a single fiber, but often fibers are bundled together in the center of the cable. Optical fiber are smaller and lighter than copper wire. One optical fiber is approximately the same diameter as a human hair. 2.2.1 Advantages of Fiber Optic  Noise resistance: it is immune to EMI  Less signal attenuation: signal can run for miles without requiring regeneration  Higher bandwidth: fiber optic cable can support dramatically higher bandwidths (and hence data rate) than all other cables. Currently, data rates and bandwidth utilization over fiber-optic cable are limited not by the medium but by the signal generation and reception technology available. A typical bandwidth for fiber optic is 100Mbps to 1Gbps. Led Photo Diode

CS163 CHAPTER 2: COMMUNICATION MEDIA River 2.3.2 Microwave Transmission Terrestrial microwave systems are typically used when using cabling is very costly and difficult to set. 2.3.3 Satellite Communication Satellite transmission is much like line of sight microwave transmission in which one of the stations is a satellite orbiting the earth. The principle is the same as terrestrial microwave, with a satellite acting as a super-tall antenna and repeater. Although in satellite transmission signals must still travel in straight lines, the limitations imposed on distance by the curvature of the earth are reduced. In this way, satellite relays allow microwave signals to span continents and ocean with a single bounce. Satellite microwave can provide transmission capability to and from any location on earth, no mater how remote. This advantage makes high Building A Building B Satellite dish Satellite dish Satellite USA Singapore Mother Earth

CS163 CHAPTER 2: COMMUNICATION MEDIA quality communication available to undeveloped parts of the world without requiring a huge investment in ground based infrastructure. Satellite themselves are extremely expensive, of course, but leasing time or frequencies on one can be relatively cheap. 2.3.4 Infrared Transmission Infrared media uses infrared light to transmit signals. LEDs transmit the signals, and photodiodes receive the signals. The remote control we use for television, VCR and CD player use infrared technology to send and receive signals. Because infrared signals are in high frequency range, they have good throughput. Infrared signals do have a downside; the signals cannot penetrate walls or other objects, and they are diluted by strong light sources. Summary Table of the Characteristic of Wireless Communication Media Factor Terrestrial Microwave Satellite Microwave Infrared Transmission Cost Moderate to high High Moderate to high Installation About 1 to 10Mbps About 1 to 10Mbps 100Kps to 16Mbps Bandwidth capacity About 1 to 10Mbps About 1 to 10Mbps 100Kbps to 16Mbps Node capacity per segment 2 (sender and receiver) 2 (sender and receiver) 2 (sender and receiver) Attenuation Depends on condition (affected by atmospheric conditions) Depends on condition (affected by atmospheric conditions) Depends on condition (affected by atmospheric conditions) Security Depends on condition (affected by atmospheric conditions) Depends on condition (affected by atmospheric conditions) Depends on condition (affected by atmospheric conditions)

CS163 CHAPTER 2: COMMUNICATION MEDIA d) electricity

5. Smoke signal are an example of communication through ………. a) a guided medium b) an unguided medium c) a refractive medium d) bounded medium
6. If a satellite is in geosynchronous orbit, it completes one orbit in … a) one hour b) 24 hours c) one month d) one year
7. If a satellite is in geosynchronous orbit, its distance from the sending station … a) is constant b) varies according to the time of day c) varies according to the radius of the orbit d) none of above
8. Optical fibers, unlike wire media, are highly resistant to … a) high frequency transmission b) low frequency transmission c) electromagnetic interference d) refraction Answer the following questions:
9. Explain what is attenuation.
10. What do you understand by guided and unguided communication media. List three example of each.
11. Twisted pair cables are twisted in a helical form, what purpose does it serve. Explain with the aid of diagram.
12. Give two advantages and disadvantages of using twisted pair over coaxial cable.
13. Give two advantages and disadvantages of using coaxial cable over twisted pair.
14. Briefly explain two types of coaxial cable.
15. Describe the components of a fiber optic cable.
16. Give three advantages and disadvantages of using fiber optic cable over metallic cable.
17. Compare twisted pair, coaxial cable, and fiber optic cable based on following factor:  Cost  Installation  Bandwidth capacity  Attenuation  EMI

CS163 CHAPTER 2: COMMUNICATION MEDIA

10. What is line of sight transmission.
11. describe the components of a satellite communication.
12. With the aid of diagram explain how
    13. Compare microwave, satellite, and infrared transmission system, based on following factor:  Cost  Installation  Bandwidth capacity  Attenuation