1. Computer Communications

2. Hi! I am Prof.Doug Lyon I Welcome you to this class

3. Computer Communications I: System Analysis Course Number : CpE 471 Meets : Monday 5-7:30 Room :Dana 123 Prof : Doug Lyon Office Hours :1:30–2:30 MWF and by appointment

4. Computer Communications I: System Analysis Text: Data and Computer communications by William Stallings, MacMillan Co. Fourth Edition

5. Grading Home work is optional Attendance is optional Final is optional Grade is average quiz score

6. Grading A 15 min. cumulative open-book/ open-notes calculators permitted quiz every week (but not today!) Next quiz 9/13/93 since no class 9/6/93

7. Grading Lowest two quizzes dropped (or are optional, i.e. sick days) You MUST pick one of the following: Final = 4 quiz grades

8. PROJECT Project = 4 quiz grades You will be responsible for obtaining software for your project. STELLA should be at the book store. STELLA is optional. Call them at 603-643-9636 for a copy

9. PROJECT Project examples: Symbolic Computation, teaching aids, functional simulation etc. See me for projects. Paper = 4 quiz grades. Survey of approved journal articles

10. Topics include,but are not limited to,(by chapter) TOPICS: Week 1-History,architectural overview and design issues in computer communications.CH1 Outline

11. Week2-Theoretical basis for data communications,bandwidth-limits, data transmission,signal parameters, media,attenuation delay. Fourier analysis.Fiber optics. CH 2.1,2.2

12. Outline Week3-Data encoding,Modulation Techniques.Information Theory. FM,AM,PM,sampling Theorem, coding,Modems,RS232 interfacing,serial standards,CH-2.3 Week4,5-Digital TransmissionPCM encodingsystems,X.21,AX.21. CH2.4

13. Outline Week6-Transmission and switching FDM,TDM,STDM.Multiplexing ISDN. CH 2.5,2.6 Week 7-Coding and interface standards,error detection and interfacing.

14. Outline Week 8,9-Data link control,control of retransmission,HDLC protocol

15. PROJECT T he project and paper are due on 11/29/93 (day after Thanksgiving weekend). A late project has 10 points out of 100 removed from the project grade per day late, resulting in a 0 after 12/9/93

16. Outline Week 10-Introduction to Queueing Theory,M/M/ 1, networks of M/M/1, queues,simulating queueing systems,applications of queueing.CH: Appendix A

17. Outline Week 11-Circuit switching,virtual curcuits, packet switching and datagram packet switching.ATM,data kit.

18. Outline Week 12-Circuit switching,PBX,Networkcontrol, routing algorithms for point- top-point networks. Week 13-Packet switching,virtual circuits and datagrams.Routing Algorithms. Hardware networks.

19. Outline Week 14-Radio and satellite networks:Explores design and performance issues for antenna- based communication nets.Wireless packet radio systems

20. Outline Week 15-LANs,examine CSMA/CD, various topologies,alternative mediums and access control techniques.

21. A COMMUNICATION MODEL

22. DATA COMMUNICATION NETWORK comm.net comm net node net station i.e computer terminal or telephone

23. DATA COMMUNICATION NETWORKS Communication networks switched unswitched

24. Switched Circuit Switched Packet Switched DATA COMMUNICATION NETWORKS

25. Unswitched(broadcast nets) DATA COMMUNICATION NETWORKS packet radio satellite local Packet switched nets are store and forward nets.

26. ckt switched nets have dedicated communication paths (i.e. telephone) For example: DATA COMMUNICATION NETWORKS A Broadcast Comm. Net can be WAN, the media is unshared

27. DATA COMMUNICATION NETWORKS Dish LAN EXAMPLES:

28. DATA COMMUNICATION NETWORKS Ethernet with a bus topology:

29. DATA COMMUNICATION NETWORKS Ring topology net: Note: No switching nodes,media is shared in LAN For packet radio,every station can hear every other, the media is shared so this is a LAN technology

30. DATA COMMUNICATION NETWORKS Agent input devicetransmitterchannel channel receiver output device This course addresses the communication systems parts between the input and output devices.

31. Computer Communications Architecture The Three Layer Model Application run on computer which use networks network layer - xchange of data between computer and network transport layer - error detection and correction application layer - file xfer etc.

32. Computer Communications Architecture File xfer modules xmits passwords file commands file records

33. Computer Communications Architecture communications service module – error correction – encryption – keeps track of data to ensure delivery Network Access Module - net specific stuff

34. Computer Communications Architecture

35. The transport layer will break data into chunks adds control information and this is called a PDU or protocol data unit Network access layer is told which computer but not which SAP (SAP) service acess points 1 2 and 3 are used to uniquely identify the application communicating

36. Computer Communications Architecture

37. Protocol Data Units TPDU1 = transport protocol data unit := transport hdr, chunk1 TPDU2 = transport hdr, chunk2 NPDU = network protocol data unit network hdr, TPDU

38. Protocol Data Units Application data = chunk1 + chunk2 +... Destination SAP (service access points) TPDU has destination SAP so that appropriate application obtains data

39. Protocol Data Units Sequence # TPDU’s may be sent in any order,and by different routes and may arrive at different times. TPDU may have error detection or correction codes built-in NPDU destination address (i.e. IP address) facilities requires (i.e. priority)

40. Transmission Terminology point-to-point :- guided transmission is unshared I.e. O(N**2) connectivity (completely connected) = number of links

41. Transmission Terminology Multipoint guided transmission allows shared medium

42. Transmission Terminology ANSI Defs: – simplex - one direction only – half-duplex - two-way but not at the same time. – full-duplex - simultaneous two way transmission

43. Transmission Terminology CCITT – CCITT vs ANSI – simplex = half-duplex – duplex = full-duplex CCITT = international telegraph and telephone consultive committee

44. Analog and Digital Data Transmission data - entities which convey meaning signals - encoding of data signaling - act of sending a signal transmission - communication of data by propagation and processing of signals

45. Analog and Digital Data Transmission digital data - takes on discrete values, i.e. text integers. analog data - takes on continuously varying patterns of intensity, i.e.. sound But what is digital? What is Analog? How do we defines these things?

46. Analog and Digital Data Transmission s(t) is continuous (i.e. analog) iff for all a

47. Analog and Digital Data Transmission A signal, s(t) is discrete iff for some a For example, the function s(t) has multiple values or does not exist and there fore the limit does not exist.

48. Analog and Digital Data Transmission Let the function f be defined on the set S. f is continuous at a point P0 of S iff whenever

49. Analog and Digital Data Transmission If f is defined on an interval [a, b] and is continuous at then given an

50. DATA and SIGNALS Modem (modulator/demodulator) modulation involves two waveforms: The modulating signal (the message) and the carrier wave which is altered by the modulating signal The complementary process is called demodulation Bits modem analog signal modem bits

51. DATA and SIGNALS Codec := coder-decoder analog codec bits In General a digital waveform has infinite bandwidth. Band limited channels low-pass filter square waves, this rounds their corners. Rule of thumb: if a signal is W bps, you may need 2W Hz bandwidth.

52. Signal Strenth attenuation := a loss of signal strength – signal strength falls off logarithmically so the decibel is used to measure the loss – Decibel gains and losses are computed via simple addition and subtraction.

53. Signal Strenth Let number of decibels

54. Signal Strenth Example loss=10log(5/10)=-3 dB

55. Signal Strenth dBw=decibel watt

56. Signal Strenth

57. About Those Exponents... The Laws of Exponents give us the laws of logarithms