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2. Computer Networks A Computer Network is a group of computers connected together and communicate with one another for a common purpose A collection of two or more computers interconnected by telephone line, coaxial cables, satellite link, radio and/or some other communication technique

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4. Networking Networking is the interconnection of workstations, peripheral( such as printer, hard drives, scanners and CD- ROM

5. www.imt.edu Networking Macintosh PC Mainframe All the devices speak the same language

6. www.imt.edu Protocol Protocol is a common language that can be understood by all devices on a network Suppose a group of people are assigned to work as a team to complete a project, it does not matter French German Indian American formal description of a set of rules and convention that govern how devices on a network exchange information

7. www.imt.edu Why and How did Networking Start Early computer were : Standalone devices It was not efficient or cost effective way for business to operate. Three problem were addressed Each computer operated on its own, independently from other computer  Duplication of equipment  Inability to communicate efficiently  Lack of Network Management

8. www.imt.edu Solution of the addressed Problem LAN (Local Area Network) WAN (Wide Area Network) Two solution LAN  Local Area Network  used within or between offices WAN  Wide Area Network  used between buildings or within a “complex”

9. www.imt.edu LAN operate within a limited geographic area allow many user to access high wand-width media provide full time connectivity to local services connect physically adjacent devices LAN connect workstations, peripherals, terminals and other devices. LAN are designed to

10. www.imt.edu WAN Business needed a way to move information efficiently and quickly from one LAN to another LAN. The solution was WAN. WAN interconnect LAN’s to provide access to computer or file server in other location, WAN connect networks that serve users across a large geographic area

11. www.imt.edu Source Computer/Source Host Device where computer messages (data) originate (start from)

12. www.imt.edu Receiving Computer/ Destination Host where data should arrive

13. www.imt.edu Data Packet encapsulated bits (data)  Binary Digits  1s and 0s extra information added to ensure reliable communication  source address  destination address used to transport messages

14. www.imt.edu Media Where the data packets travel STP, UTP, Coaxial cable, optical fiber, wireless

15. www.imt.edu Wireless Networking uses electromagnetic (EM) waves  these waves travel in a vacuum at the speed of light  in our atmosphere or in outer space  power waves, radio waves, microwaves, infrared light, violet light, visible light, ultraviolet light, x-rays, gamma rays

16. www.imt.edu Protocols The rules that govern a specific layer of communication  A set of rules that make communication more efficient  Allows data packets to travel from source to destination without misunderstanding  Technical definition: A set of rules, or an agreement, that determines the format and transmission of data

17. www.imt.edu Layer Protocols Network communication occurs layer-to- layer  Layer N on source communicates with Layer N on destination  The rules and conventions for this communication are called the Layer N Protocol

18. www.imt.edu Proprietary vs. Open Technologies Proprietary  Privately developed, owned, and controlled  One company or a small group of companies controls all usage of the technology Open  Free usage of the technology is available to the public

19. www.imt.edu Interoperability The ability of networks to communicate & work together

20. www.imt.edu The Need for standards Different H/W and S/W Different H/W and S/W Network A Network B incompatible and it became difficult for the networks using different specification to communicate with each other. Mid 1980’s Tremendous increase in the number of networks Many different specifications and implementations Proprietary systems in use blocked interoperability

21. www.imt.edu ISO (International Organization for Standards) To address the problem of networks being incompatible and unable to communicate with each other, the International Organization for standardization(ISO), in order to find a set of rules. ISO recognized that Became the primary architectural model for inter computer communication.

22. www.imt.edu Open Systems Interconnection Model (OSI) OSI is the international framework of standards for communication between different systems. Developed by the International Organization for Standardization in 1984. It consists of seven layers.

23. www.imt.edu Use the OSI model to visualize how information (data packets) travels from applications on one computer, through networking media, to an application on another computer

24. www.imt.edu All People Seem To Need Data Processing Why a layered Network Model

25. www.imt.edu OSI Model Layers The highest layer (the application layer) is closest to the user. The lowest layer (the physical layer) is closest to the media technology. Each layer has a different but specific processing function.

26. www.imt.edu Host and Media Layers

27. www.imt.edu The OSI model is like a blueprint for a building car. After a car blueprint is complete, the car must still be built

28. www.imt.edu OSI Model Application Layer

29. www.imt.edu 7. The Application Layer Closest to user Deals with network application such as : File transfer, e-mail, telnet, network management BROWSERS

30. www.imt.edu OSI Model Presentation Layer

31. www.imt.edu 6. The Presentation Layer Ensures that data sent by the application layer of one system is readable by the application layer of another system Encryption, decryption, compression, and decompression. If needed, translates between multiple data formats using a COMMON DATA FORMAT

32. www.imt.edu OSI Model Session Layer

33. www.imt.edu 5. The Session Layer Responisble for establishing a session or logical connection between two application. Provides services to the presentation layer

34. www.imt.edu OSI Model Transport Layer

35. www.imt.edu 4. The Transport Layer Segments data from the sending host & reassembles data on the receiving host Shielding boundary between upper 3 layers (application issues) & lower 3 layers (data transport issues) Establishes, maintains, and terminates virtual circuits (No hardware at this level - all software). Error detection-and-recovery Information flow control QUALITY OF SERVICE, RELIABILITY

36. www.imt.edu OSI Model Network Layer

37. www.imt.edu 3. The Network Layer Provides connectivity and best path selection between two end systems Data is formatted into data packets. Determines the proper path - routing. IP addressing (logical addressing). Packet switching occurs at this layer. Domain of routing PATH SELECTION, ROUTING, ADDRESSING Router

38. www.imt.edu OSI Model Data Link Layer

39. www.imt.edu 2. The Data Link Layer Provides reliable transfer of frames across a physical link (media) Frames are organized in a specified format Responsible for flow control, error detection and correction technique. Functions Framing, error control, flow control and medium access (in shared networks) Bridges and switch

40. www.imt.edu OSI Model Physical Layer

41. www.imt.edu Other layer deals with 0’s and 1’s the physical layer defines the rules for turning those ones and zeroes into electrical signal going out over a copper cable 01001010101101010 NIC 01001010101101010 NIC The repeater takes a electrical signal received from one segments of cable, converts it into binary code, and then converts the binary code back into the a physical signal on the other segments.

42. www.imt.edu 1. The Physical Layer Sends and receives bits has two responsibility : sending and receiving data Defines the electrical and functional specification for activating and maintaining the link between the system Wires, connectors, voltages, data rates SIGNALS, MEDIA Repeaters, hubs, cabling Repeaters, hubs, cabling

43. www.imt.edu Protocol Data Units Different layers in the OSI model have different groupings for data Each layer has a protocol data unit, or PDU Transport layer deals with segments Network layer encapsulates segments into packets Data Link layer encapsulates packets into frames Physical layer converts frames to bit streams

44. www.imt.edu Encapsulation Packaging of data for transmission Data flows down the levels of the source and then up the levels of the destination 5 encapsulation steps:  Build data  Transport layer segments data  Network layers puts data into a packet with header information  Data Link layer puts packet into a frame  Physical Layer converts frame to bits

45. www.imt.edu Data Encapsulation Example

46. www.imt.edu Peer-to-Peer Communication

47. www.imt.edu A Bit of History The TCP/IP Model was develop by the Department of Defense in the late 60s’ to ensure data communications would not be interrupted even under the worse circumstances. Since then, TCP/IP has become the de facto method we use for data communications on the Internet.

48. www.imt.edu The TCP/IP reference model the de facto Internet standard demonstrates arbitrary nature of layers  various models are possible  OSI & TCP/IP are the two most important

49. www.imt.edu The TCP/IP reference model Specifications for development:  information flows regardless of the condition of the network  packets get to their destination every time  packets can travel from any point to any other point TCP/IP resulted  DoD project  standard on which the Internet has grown

50. www.imt.edu Layers of the TCP/IP model Four layers:  A pplication  T ransport  I nternet  N etwork Access IMPORTANT--even though the names may be the same as the OSI layers, do not confuse the layers of the two models. The layers include different functions in each model.

51. www.imt.edu Application Transport Network Access Internet TCP/IP OSI Application Presentation Session Transport Network Data Link Physical

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53. The Four Layers of TCP/IP Application Includes all the functions of the OSI’s Application, Presentation, & Session layers including: Data representation Data encryption and Dialog control

54. www.imt.edu The Four Layers of TCP/IP Application Transport Uses the TCP protocol and is responsible for quality of service issues including: Reliability Flow Control and Error Correction

55. www.imt.edu The Four Layers of TCP/IP Application Transport Internet Uses the IP protocol and is responsible for: Path determination and Packet switching.

56. www.imt.edu The Four Layers of TCP/IP Application Transport Network Access Internet Includes all the functions of the OSI’s Data Link & Physical layers including: processes required by IP to ensure a packet reaches its destination. all the various LAN & WAN Technologies such as 100BaseTX & Frame Relay.

57. www.imt.edu Application Layer One application layer handles all high- level protocols  Includes the functions of the OSI Presentation & Session layers  Assumes data is properly packaged for the next layer Handles issues of representation, encoding, and dialog control

58. www.imt.edu Transport Layer Quality of service  Reliability, flow control, error correction Uses TCP protocol  Transmission Control Protocol  Reliable, low-error  Packages application layer data into segments

59. www.imt.edu Internet Layer Sends source packets across the internetwork independent of path Uses IP  Internet Protocol Best Path determination Packet Switching  Logical connection formed by packets between hosts

60. www.imt.edu Network Access Layer Also Host to Network layer Deals with issues that an IP packet requires to actually make a physical link Includes LAN & WAN technology Includes all the OSI physical and data link layer details

61. www.imt.edu Protocols For Each Layer FTP-File Transfer Protocol HTTP-Hypertext Transfer Protocol SMTP-Simple Mail Transfer Protocol DNS-Domain Name Service TFTP-Trivial File Transfer Protocol Application

62. www.imt.edu Protocols For Each Layer TCP-Transmission Control Protocol UDP-User Datagram Protocol Transport Application

63. www.imt.edu Protocols For Each Layer IP-Internet Protocol Internet Transport Application

64. www.imt.edu Protocols For Each Layer LAN & WAN Technologies Network Access Internet Transport Application

65. www.imt.edu Comparing TCP/IP with OSI

66. www.imt.edu Comparing TCP/IP with OSI Similarities  both have layers  both have application layers, though they include very different services  both have comparable transport and network layers  packet switched (not circuit switched) technology is assumed  networking professionals need to know both

67. www.imt.edu Comparing TCP/IP with OSI Differences  TCP/IP combines the presentation and session layer issues into the application layer  TCP/IP combines the OSI data link layer and physical layers into one layer--the network access layer  TCP/IP appears simpler because it has fewer layers  TCP/IP protocols are the standards around which the Internet is built

68. www.imt.edu Although the OSI model is universally recognized, the historical and technical open standard of the Internet is the TCP/IP reference model and the TCP/IP protocol stack. TCP/IP makes data communication between any two computers, anywhere in (or outside of) the world, at nearly the speed of light,and has historical importance - such as the standards that allowed the telephone, electric, railroad, television, and videotape industries to flourish.

69. www.imt.edu Conceptual nature of the OSI model No networks are built around specific OSI protocols Everyone uses the OSI model to guide their thinking  You will use the OSI model, but the TCP/IP protocols

70. www.imt.edu What the OSI Model Provides to Vendors Standards ensuring greater compatibility and interoperability between the various types of network technologies in existence IBM’S SNA DECNET TCP/IP