1. CSCI 370 CSCI-370 C omputer Networks: Shrinking the globe one click at a time Lecture 2 Khurram Kazi

2. Major sources of the slides for this lecture  Slides from Tanenbaum’s and William Stallings’ website are used in this lecture K KaziCSCI 370 2

3. Mankind and Communication  “ O mankind! We have created you from a single (pair) of a male and female, and have made you into nations and tribes, so that you may know each other … ” [Quran 49.13]  When one ponders over how we get to know each other; certain thoughts come to mind.  As we venture outside our own region or domain, we tend to follow certain protocols that allow us to communicate with each other.  Try to use common language that both parties understand  Sign language  Draw pictures, use hand gestures…  In short we find a command ground or similar footing which to build a communication platform on, even though we may come from diverse cultures and background K KaziCSCI 370 3

4. Mankind and Communication  Just as we have diversity in mankind, we have disparate, ever-evolving communications networks  These networks are evolving towards providing seamless connectivity between different platforms and applications so that they cater to our insatiable need to communicate  An integral component of networking is PROTOCOLS K KaziCSCI 370 4

5. OSI: A Model developed by International Standards Organization (ISO)  Open Systems Interconnection  Developed by the International Organization for Standardization (ISO) has seven layers  Is a theoretical system delivered too late!  TCP (Transmission Control Protocol) /IP is the de facto standard K KaziCSCI 370 5

6. Networking Reference Models  The OSI Reference Model  The TCP/IP Reference Model K KaziCSCI 370 6

7. TCP/IP Protocol Architecture  developed by US Defense Advanced Research Project Agency (DARPA)  for ARPANET packet switched network  used by the global Internet  protocol suite comprises a large collection of standardized protocols K KaziCSCI 370 7

8. OSI vs. TCP/IP  The OSI & TCP/IP reference model. K KaziCSCI 370 8

9. Reference Models  Protocols and networks in the TCP/IP model initially. K KaziCSCI 370 9

10. Key Elements of a Protocol  syntax - data format  semantics - control info & error handling  timing - speed matching & sequencing K KaziCSCI 370 10

11. Simplified Network Architecture K KaziCSCI 370 11

12. TCP/IP Layers  no official model but a working one  Application layer  Host-to-host, or transport layer  Internet layer  Network access layer  Physical layer K KaziCSCI 370 12

13. Physical Layer  concerned with physical interface between computer and network  concerned with issues like:  characteristics of transmission medium  signal levels  data rates  other related matters K KaziCSCI 370 13

14. Network Access Layer  exchange of data between an end system and attached network  concerned with issues like :  destination address provision  invoking specific services like priority  access to & routing data across a network link between two attached systems  allows layers above to ignore link specifics K KaziCSCI 370 14

15. Internet Layer (IP)  routing functions across multiple networks  for systems attached to different networks  using IP protocol  implemented in end systems and routers  routers connect two networks and relays data between them K KaziCSCI 370 15

16. Transport Layer (TCP)  common layer shared by all applications  provides reliable delivery of data  in same order as sent  commonly uses TCP K KaziCSCI 370 16

17. Application Layer  provide support for user applications  need a separate module for each type of application K KaziCSCI 370 17

18. Operation of TCP and IP K KaziCSCI 370 18

19. Addressing Requirements (will discuss at length in later lectures)  two levels of addressing required  each host on a subnet needs a unique global network address  its IP address  each application on a (multi-tasking) host needs a unique address within the host  known as a port K KaziCSCI 370 19

20. Operation of TCP/IP K KaziCSCI 370 20

21. Transmission Control Protocol ( TCP)  usual transport layer is (TCP)  provides a reliable connection for transfer of data between applications  a TCP segment is the basic protocol unit  TCP tracks segments between entities for duration of each connection K KaziCSCI 370 21

22. TCP Header K KaziCSCI 370 22

23. User Datagram Protocol (UDP)  an alternative to TCP  no guaranteed delivery  no preservation of sequence  no protection against duplication  minimum overhead  adds port addressing to IP K KaziCSCI 370 23

24. UDP Header K KaziCSCI 370 24

25. IP Header K KaziCSCI 370 25

26. IPv6 Header K KaziCSCI 370 26

27. TCP/IP Applications  have a number of standard TCP/IP applications such as  Simple Mail Transfer Protocol (SMTP)  File Transfer Protocol (FTP)  Telnet K KaziCSCI 370 27

28. Some TCP/IP Protocols K KaziCSCI 370 28

29. Network Design: Software & Hardware  Protocol Hierarchies  Design Issues for the Layers  Connection-Oriented and Connectionless Services  Service Primitives  The Relationship of Services to Protocols K KaziCSCI 370 29

30. Design Issues for the Layers  Addressing  Error Control  Flow Control  Multiplexing  Routing K KaziCSCI 370 30

31. Connection-Oriented and Connectionless Services  Six different types of service. K KaziCSCI 370 31

32. Service Primitives  Five service primitives for implementing a simple connection- oriented service. K KaziCSCI 370 32

33. Service Primitives (2)  Packets sent in a simple client-server interaction on a connection-oriented network. K KaziCSCI 370 33

34. Starting from the bottom layer of the TCP/IP working model  Physical Layer:  Getting into the Fundamentals K KaziCSCI 370 34

35. The Theoretical Basis for Data Communication Fourier Analysis Bandwidth-Limited Signals Maximum Data Rate of a Channel K KaziCSCI 370 35

36. Bandwidth-Limited Signals A binary signal and its root-mean- square Fourier amplitudes. (b) – (c) Successive approximations to the original signal. K KaziCSCI 370 36

37. Bandwidth-Limited Signals (2) (d) – (e) Successive approximations to the original signal. K KaziCSCI 370 37

38. Guided Transmission Data Magnetic Media Twisted Pair Coaxial Cable Fiber Optics K KaziCSCI 370 38

39. Twisted Pair: Widely used in Telephony and Ethernet cabling (a) Category 3 UTP. (b) Category 5 UTP. K KaziCSCI 370 39

40. Coaxial Cable: Primarily used in Cable networks A coaxial cable. K KaziCSCI 370 40

41. Fiber Optics: Widely used in high speed networks (a) Three examples of a light ray from inside a silica fiber impinging on the air/silica boundary at different angles. (b) Light trapped by total internal reflection. K KaziCSCI 370 41

42. Transmission of Light through Fiber Attenuation of light through fiber in the infrared region. K KaziCSCI 370 42

43. Fiber Cables (a) Side view of a single fiber. (b) End view of a sheath with three fibers. K KaziCSCI 370 43

44. Fiber Cables (2) A comparison of semiconductor diodes and LEDs as light sources. K KaziCSCI 370 44

45. Fiber Optic Networks A fiber optic ring with active repeaters. K KaziCSCI 370 45

46. Wireless Transmission The Electromagnetic Spectrum Radio Transmission Microwave Transmission Infrared and Millimeter Waves Lightwave Transmission K KaziCSCI 370 46

47. The Electromagnetic Spectrum The electromagnetic spectrum and its uses for communication. K KaziCSCI 370 47

48. Radio Transmission (a) In the VLF, LF, and MF bands, radio waves follow the curvature of the earth. (b) In the HF band, they bounce off the ionosphere. K KaziCSCI 370 48

49. Politics of the Electromagnetic Spectrum Industrial, Scientific and Medical (ISM) bands in the United States. Originally reserved internationally for the use of RF electromagnetic fields for industrial, scientific and medical purposes other than communications. K KaziCSCI 370 49

50. Lightwave Transmission Convection currents can interfere with laser communication systems. A bidirectional system with two lasers is pictured here. K KaziCSCI 370 50

51. Communication Satellites Geostationary Satellites Medium-Earth Orbit Satellites Low-Earth Orbit Satellites Satellites versus Fiber

52. Communication Satellites Communication satellites and some of their properties, including altitude above the earth, round-trip delay time and number of satellites needed for global coverage. K KaziCSCI 370 52

53. Communication Satellites (2) The principal satellite bands. K KaziCSCI 370 53

54. Public Switched Telephone System Structure of the Telephone System The Politics of Telephones The Local Loop: Modems, ADSL and Wireless Trunks and Multiplexing Switching K KaziCSCI 370 54

55. Structure of the Telephone System (a) Fully-interconnected network. (Mesh network) (b) Centralized switch. (c) Two-level hierarchy. K KaziCSCI 370 55

56. Structure of the Telephone System (2) A typical circuit route for a medium-distance call. K KaziCSCI 370 56

57. Major Components of the Telephone System Local loops  Analog twisted pairs going to houses and businesses Trunks  Digital fiber optics connecting the switching offices Switching offices  Where calls are moved from one trunk to another K KaziCSCI 370 57

58. The Local Loop: Modems, ADSL, and Wireless The use of both analog and digital transmissions for a computer to computer call. Conversion is done by the modems and codecs (CoDecoder). K KaziCSCI 370 58

59. Modems (a) A binary signal (b) Amplitude modulation (c) Frequency modulation (d) Phase modulation K KaziCSCI 370 59