1. Module E: Network BASICS

2. INTRODUCTION Computer network – two or more computers connected so that they can communicate with each other and share information, software, peripheral devices, and/or processing power

3. INTRODUCTION

4. Number of connections For n nodes, you would need n(n-1)/2 connections For examples to connect 5 nodes we would need 5 (5-1)/2=10 connections

5. Basic Principles of Networks Four main principles 1. Each computer must have a network interface to provide a doorway for information 2. The network usually has at least one connecting device 3. The network must have communications media to transport information

6. Basic Principles of Networks 4. Each computer must have software to move information in and out of the computer These four principles apply to all networks, large and small

7. HOME NETWORKS A typical home network setup has 1. An Ethernet network card in each computer or a wireless card in each laptop 2. Network cables to transmit signals, or no cables for wireless 3. A DSL or cable modem connection and a broadband/home router

8. Network Cards Network interface card (NIC) – an expansion card or PC card that connects your computer to a network Ethernet card – the most common type of network interface card Built into the motherboards of many new computers – looks like a telephone jack, but wider

9. Wired Transmission Media Cat 5 (Category 5) cable – better- constructed version of phone twisted-pair cable

10. Wireless Transmission Media Wireless Access Point (WAP) – device that allows a computer to use radio waves to access a network Connects to hub or switch with a cable like a wired computer May be built into broadband router and not require separate cabling

11. Home Internet Service Broadband router or home router – a device to connect computers together to share DSL or cable Internet service in a home or small office One port to plug into DSL or cable connection to connect to the Internet Usually several ports to build a network for home computers or printers and share Internet connection

12. Network Software Makes each computer's hardware work Can use Windows Turn on filesharing to make files available to other computers on the network

13. NETWORK COMPONENTS Hub – a device that connects computers into a network and repeats all transmissions to every connected computer Only one computer can transmit at a time All computers see every message Can have collisions when two computers try to transmit at the same time

14. NETWORK COMPONENTS Switch – a device that connects computers and repeats transmissions only to intended recipient Multiple conversations can occur simultaneously between different sets of computers Only recipient computer sees each message Computers can still broadcast messages to all other computers on the network

15. NETWORK COMPONENTS Router – a device that connects subnetworks (subnets) of a larger network Can connect different buildings at same or different locations Passes transmissions from one network to another May pass through multiple routers on the way from source to destination

16. NETWORK COMPONENTS More on routers Home/broadband routers often have built- in switches or hubs Corporate routers generally require separate switches or hubs Routers must be configured with information about the networks they connect

17. NETWORKS BY DISTANCE Large networks can be classified by the proximity of the area(s) they serve: Local Area Network (LAN) – network that serves a building or buildings in a contiguous area

18. NETWORKS BY DISTANCE More networks by distance Wide Area Network (WAN) – a set of connected networks serving areas not immediately contiguous Metropolitan Area Network (MAN) – a set of connected networks within the same city or metropolitan area but not in immediate proximity to each other

19. THE INTERNET A vast network of computers that connects people all over the world Computers pass messages through routers to their ultimate destinations Each router determines whether it has a direct path to the recipient or whether to send the message on to another router

20. Bandwidth The amount of information that can be transferred in a given amount of time Usually expressed as bits per second (bps) Higher bandwidths expressed as kilobits per second (Kbps) – thousands of bits per second megabits per second (Mbps) – millions of bits per second gigabits per second (Gbps) – billions of bits per second

21. Internet Connection Types Phone line and dialup modem Phone line and DSL modem Cable TV line and cable modem Satellite modem Dedicated high-speed business lines

22. Broadband Internet Connection Broadband – high-capacity telecommunications line capable of providing high-speed Internet service All Internet access methods on the previous slide are broadband except the dialup modem

23. Dialup Connection Modem – connects a computer to a phone line to access another computer or network Modulates outgoing signal from digital to analog form Demodulates incoming signal from analog to digital form

24. Digital Subscriber Line (DSL) Digital Subscriber Line (DSL) – high- speed Internet connection using phone lines, which allows you to use your phone for voice communications at the same time Runs at a higher frequency than voice conversations, so not supported on some older phone lines

25. Cable Modem Cable modem – uses your TV cable to deliver an Internet connection

26. Satellite Modem Satellite modem – delivers Internet access from satellite dish Satellite TV and modem may share same dish or may be separate Connects to computer or broadband router like cable modem

27. T1 and DS3 Business Lines T1 and DS3 developed by phone companies to carry many long-distance voice conversations T1 runs up to about 1.5 Mbps DS3 runs up to about 45 Mbps Can carry both voice and network over the same lines

28. Frame Relay and ATM Business Services Frame Relay and ATM are used to connect many branch offices to the main office Use virtual circuits to simulate having a line from every office to every other office Virtual Circuits

29. Comparison of Connection Types Telephone modem + Inexpensive and available anywhere there's a phone line - Slow, and ties up the line for voice calls too DSL + Higher-speed connection, doesn't tie up the phone line for voice calls, and can be left on all the time - Not available in all areas or on all lines

30. Comparison of Connection Types Cable modem + Higher-speed connection, doesn't use the phone line at all, and always-on - Connection shared with the neighborhood, so speed may vary Satellite modem + Available in remote locations where DSL and cable aren't - High cost

31. Comparison of Connection Types T1 and DS3 + High-speed to very-high-speed connections, can transmit both voice and data - High cost that may be mileage-dependent Frame relay and ATM + Use virtual circuits to simulate more inter- office connections than are physically present - High cost normally affordable only by mid- to large-scale enterprises

32. Voice Over IP Voice over IP – allows you to send voice communications over the Internet and avoid long-distance toll charges No long-distance calling cost

33. NETWORK COMMUNICATIONS MEDIA Communications media – the paths in a network over which information travels Wired communications media – transmit information over a closed, connected path Wireless communications media – transmit information through the air

34. Wired Communications Media Twisted-pair cable – a bundle of copper wires for transmitting voice or data Cat 5 and Cat 5e are common for modern networks Coaxial cable (coax) – one central wire surrounded by insulation, a metallic shield, and a covering of insulation

35. Wired Communications Media Optical fiber – uses a very thin glass or plastic fiber through which pulses of light travel

36. Wireless Communications Media Infrared – uses red light to send and receive information Bluetooth – a standard for transmitting information in the form of short-range radio waves over distances of up to 30 feet and is used for purposes such as wirelessly connecting a cell phone or PDA to a computer Microwave – a type of radio transmission Repeater – receives a radio signal, strengthens it, and sends it on

37. Wireless Communications Media

38. Communications Satellite – microwave repeater in space

39. NETWORK SECURITY The four principles of network security are: 1. Confidentiality 2. Authenticity 3. Integrity 4. Availability

40. NETWORK SECURITY Confidentiality – information can be obtained only by those authorized to access it Bank statements, credit reports, employee evaluations Threatened by capture of network transmissions and easily-guessed passwords

41. NETWORK SECURITY Authenticity – information really comes from the source it claims to come from Military orders, medical diagnoses, stockbroker directions Threatened by fraudulent e-mails and misspellings of popular Web site names

42. NETWORK SECURITY Integrity – information has not been altered Bank balance, corporate Web site, prescriptions, credit card charges Threatened by forged network transmissions and faulty server software

43. NETWORK SECURITY Availability – a service or resource is available when it's supposed to be Mail-order Web site, corporate e-mail server Threatened by network failures, faulty server software, and high volumes of malicious network traffic

44. Firewalls & Intrusion Detection Systems Firewall – protects a computer from intruders Intrusion detection system (IDS) – watches for and reports intrusion attempts Intrusion prevention system (IPS) – type of IDS that also takes action against intrusion attempts

45. Encryption Encryption – scrambles data so you can't read it without having the decryption key Virtual Private Network (VPN) – encrypts all network transmissions between two endpoints to protect confidentiality and integrity of data

46. Firewalls & Intrusion Detection Systems

47. Malware Malware – software designed to harm your computer or security 1. Virus – software written with malicious intent to cause annoyance or damage 2. Worm – spreads itself from computer to computer via e-mail and other network traffic 3. Spyware – collects information about you and reports it to someone else without your permission

48. CLIENT/SERVER SOFTWARE MODEL Client/server network – a network in which one or more computers are servers and provide services to the other computers, called clients

49. Client/Server: A Business View Client/server networks differ according to 1. Where the processing for the presentation of information occurs 2. Where the processing of logic or business rules occurs 3. Where the data management component (DBMS) and information (database) are located

50. Client/Server: Model 5

51. Five Models of Client/Server

52. 1. Distributed Presentation The server handles almost all functions, including a major portion of the presentation 2. Remote Presentation The client handles all presentation functions 3. Distributed Logic The server handles all data management, the client handles all presentation formatting, and the logic processing is shared

53. Five Models of Client/Server 4. Remote Data Management The server handles data management only, and the client processes business rules and formats the presentation of results 5. Distributed Data Management The client handles all presentation formatting and business rule processing, and both the server and client share data management duties