1. Fall 2008CSCI 690 CSCI-690 C omputer Networks: Shrinking the globe one click at a time Lecture 2 Khurram Kazi

2. Fall 2008 CSCI 690 2 Major sources of the slides for this lecture  Slides from Tanenbaum’s and William Stallings’ website are used in this lecture

3. Fall 2008 CSCI 690 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

4. Fall 2008 CSCI 690 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

5. Fall 2008 CSCI 690 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

6. Fall 2008 CSCI 690 6 Networking Reference Models  The OSI Reference Model  The TCP/IP Reference Model

7. Fall 2008 CSCI 690 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

8. Fall 2008 CSCI 690 8 OSI vs. TCP/IP  The OSI & TCP/IP reference model.

9. Fall 2008 CSCI 690 9 Reference Models  Protocols and networks in the TCP/IP model initially.

10. Fall 2008 CSCI 690 10 Key Elements of a Protocol  syntax - data format  semantics - control info & error handling  timing - speed matching & sequencing

11. Fall 2008 CSCI 690 11 Simplified Network Architecture

12. Fall 2008 CSCI 690 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

13. Fall 2008 CSCI 690 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

14. Fall 2008 CSCI 690 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

15. Fall 2008 CSCI 690 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

16. Fall 2008 CSCI 690 16 Transport Layer (TCP)  common layer shared by all applications  provides reliable delivery of data  in same order as sent  commonly uses TCP

17. Fall 2008 CSCI 690 17 Application Layer  provide support for user applications  need a separate module for each type of application

18. Fall 2008 CSCI 690 18 Operation of TCP and IP

19. Fall 2008 CSCI 690 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

20. Fall 2008 CSCI 690 20 Operation of TCP/IP

21. Fall 2008 CSCI 690 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

22. Fall 2008 CSCI 690 22 TCP Header

23. Fall 2008 CSCI 690 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

24. Fall 2008 CSCI 690 24 UDP Header

25. Fall 2008 CSCI 690 25 IP Header

26. Fall 2008 CSCI 690 26 IPv6 Header

27. Fall 2008 CSCI 690 27 TCP/IP Applications  have a number of standard TCP/IP applications such as  Simple Mail Transfer Protocol (SMTP)  File Transfer Protocol (FTP)  Telnet

28. Fall 2008 CSCI 690 28 Some TCP/IP Protocols

29. Fall 2008 CSCI 690 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

30. Fall 2008 CSCI 690 30 Design Issues for the Layers  Addressing  Error Control  Flow Control  Multiplexing  Routing

31. Fall 2008 CSCI 690 31 Connection-Oriented and Connectionless Services  Six different types of service.

32. Fall 2008 CSCI 690 32 Service Primitives  Five service primitives for implementing a simple connection- oriented service.

33. Fall 2008 CSCI 690 33 Service Primitives (2)  Packets sent in a simple client-server interaction on a connection-oriented network.

34. Fall 2008 CSCI 690 34 Starting from the bottom layer of the TCP/IP working model  Physical Layer:  Getting into the Fundamentals

35. Fall 2008 CSCI 690 35 The Theoretical Basis for Data Communication Fourier Analysis Bandwidth-Limited Signals Maximum Data Rate of a Channel

36. Fall 2008 CSCI 690 36 Bandwidth-Limited Signals A binary signal and its root-mean- square Fourier amplitudes. (b) – (c) Successive approximations to the original signal.

37. Fall 2008 CSCI 690 37 Bandwidth-Limited Signals (2) (d) – (e) Successive approximations to the original signal.

38. Fall 2008 CSCI 690 38 Guided Transmission Data Magnetic Media Twisted Pair Coaxial Cable Fiber Optics

39. Fall 2008 CSCI 690 39 Twisted Pair: Widely used in Telephony and Ethernet cabling (a) Category 3 UTP. (b) Category 5 UTP.

40. Fall 2008 CSCI 690 40 Coaxial Cable: Primarily used in Cable networks A coaxial cable.

41. Fall 2008 CSCI 690 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.

42. Fall 2008 CSCI 690 42 Transmission of Light through Fiber Attenuation of light through fiber in the infrared region.

43. Fall 2008 CSCI 690 43 Fiber Cables (a) Side view of a single fiber. (b) End view of a sheath with three fibers.

44. Fall 2008 CSCI 690 44 Fiber Cables (2) A comparison of semiconductor diodes and LEDs as light sources.

45. Fall 2008 CSCI 690 45 Fiber Optic Networks A fiber optic ring with active repeaters.

46. Fall 2008 CSCI 690 46 Wireless Transmission The Electromagnetic Spectrum Radio Transmission Microwave Transmission Infrared and Millimeter Waves Lightwave Transmission

47. Fall 2008 CSCI 690 47 The Electromagnetic Spectrum The electromagnetic spectrum and its uses for communication.

48. Fall 2008 CSCI 690 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.

49. Fall 2008 CSCI 690 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.

50. Fall 2008 CSCI 690 50 Lightwave Transmission Convection currents can interfere with laser communication systems. A bidirectional system with two lasers is pictured here.

51. Fall 2008 CSCI 690 51 Communication Satellites Geostationary Satellites Medium-Earth Orbit Satellites Low-Earth Orbit Satellites Satellites versus Fiber

52. Fall 2008 CSCI 690 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.

53. Fall 2008 CSCI 690 53 Communication Satellites (2) The principal satellite bands.

54. Fall 2008 CSCI 690 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

55. Fall 2008 CSCI 690 55 Structure of the Telephone System (a) Fully-interconnected network. (Mesh network) (b) Centralized switch. (c) Two-level hierarchy.

56. Fall 2008 CSCI 690 56 Structure of the Telephone System (2) A typical circuit route for a medium-distance call.

57. Fall 2008 CSCI 690 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

58. Fall 2008 CSCI 690 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).

59. Fall 2008 CSCI 690 59 Modems (a) A binary signal (b) Amplitude modulation (c) Frequency modulation (d) Phase modulation