Digital Encoding and Data Transmission

2. 5 Digital Encoding and Data Transmission

3. Objectives Give examples of digital signals. Identify the two modes of transmitting data between two points. Explain data integrity inspection using a parity check. Explain data integrity inspection using a Cyclic Redundancy Check (CRC). Explain the complete data packaging process. Compare connection-oriented transmission with connectionless data transmission.

4. Objectives Compare packet switching with circuit switching. Identify the characteristics of the various data codes. Interpret the structure and contents of a UDP frame. Compare an Ethernet II frame with an IEEE 802.3 frame. Recall the function of each layers of the OSI model.

5. Digital Signals • Measured in volts • After digital encoding, data placed on network media • Encoding marked by voltage level and time period, which represents expected digital wave shape • Unipolar digital signal • Bipolar digital signal

6. Non-Return to Zero (NRZ)

7. Manchester Encoding Binary zero is represented by transition from zero to five volts in the midpoint of time period

8. Data Transmission Modes • Synchronous transmission—Timing of digital signal important for decoding digital patterns • Asynchronous transmission—Beginning and end of data stream might be determined by: • Series of ones or zeros • Long period of no digital transmission • Various other methods

9. Data Packaging and Transmission A segment gets packaged with extra information to ensure its delivery Encapsulation process A packet travels across LANs only A frame is encapsulated and can travel across the Internet

10. Parity Check Protects against corruption such as crosstalk, loose connections, interference A Cyclic Redundancy Check (CRC) is more sophisticated error detector than parity check

11. Data Packaging Process

12. Protocols • Connection-oriented communication—Connection is terminated after data is transferred • Every frame must be verified • Results in slower data transfer speed • Connectionless communication—No need to terminate connection • Results in faster transfer speed

13. Connection-Oriented and Connectionless Communication

14. Circuit and Packet Switching Two main categories describing the way data are routed between two points Circuit switching—Permanent Internet connection Packet switching— Data broken down into packets with a source and destination address

15. Packet Switching

16. Data Codes Represent the written word Communicating systems must use the same data code Data code conversion must occur for data exchange to take place

17. ASCII Earliest attempt to standardize data codes Sometimes referred to as plain text files Used by word processing programs

18. BCD

19. EBCDIC

20. Unicode Similar to ASCII Over 65,000 possible characters Used in bar codes for scanning merchandise Used in Braille

21. Hypertext Markup Language (HTML) On web page, color code is translated into color the code represents Web browsers interpret code and create shade of color indicated

22. Protocol Frame Structures • The exact structure used is determined by the: • Purpose of communication • Type of network architecture • Use of specialized equipment and media during transfer

23. UDP Frame Structure Simple and compact protocol First 16 bits of packet identify source port Second 16 bits identify destination port Checksum uses one’s compliment to check for errors or corruption Last block of information contains actual data

24. UDP Frame

25. Ethernet Frame Structure Most common types are Ethernet II and IEEE 802.3 Generally compatible, but not guaranteed

26. Ethernet Destination Address When filled with all ones, the frame becomes a broadcast frame Multicast frame is intended for a select number of computers

27. OSI Model and Data Encoding

28. Application Layer Where user interfaces with network operating system Start and final destination of data communication

29. Presentation Layer Raw data is packaged into a universally agreed on form Data byte order is also agreed on Data encryption occurs

30. Session Layer Establishes a dialog between source and destination Negotiates decisions about how data flow is controlled and how session ends Decides on whether confirmation of arrival is needed

31. Transport Layer Responsible for flow of data to and from destination computer

32. Network Layer Provides the means of routing data packets across a WAN or MAN Uses TCP/IP protocol standards Encapsulates packets with source and destination IP addresses Responsible for virtual networks

33. Data Link Layer Converts data package into electrical pulses and places pulses on network media Subdivided into logical link control (LLC) and MAC sublayer Parity and CRC checks performed

34. Physical Layer Concerned with media, hardware, and network topology

35. Applied Networking You are installing a new network that adheres to the IEEE 10GBaseT standard. To which layers of the OSI model do the following aspects of the IEEE 10GBaseT standard relate? A. 10GBaseT network card B. Cat 6a or 6 cable C. CSMA/CD media access method 10GBaseT switch A. data link C. data link B. physical D. data link

36. Review The signal shown is an example of a _____ digital signal. A. bipolar B. unipolar B. unipolar

37. Review The signal shown is an example of a _____ digital signal. A. bipolar B. unipolar A. bipolar

38. Review The mode of data transmission in which the digital signal synchronized with a reference signal is referred to as _____. synchronous

39. Review The mode of data transmission in which the digital signal is not synchronized with a reference signal is referred to as _____. asynchronous

40. Review To perform a(n) _____, the last bit position in an 8-bit data transmission can be used for the parity code. parity check

41. Review Place data packaging process stages in sequential order starting with “segments.” A. segments B. binary code C. packets D. digital signals E. Frames A, B, C, D, E

42. Review A(n) _____ uses complicated mathematical algorithms to determine if one if more bits are corrupt. Cyclic Redundancy Check (CRC)

43. Review Which mode of communication terminates the session when all data has been transferred? A. Connection-oriented B. Connectionless A. Connection-oriented

44. Review Which mode of communication does not establish a connection before transmitting data? A. Connection-orientated B. Connectionless B. Connectionless

45. Review Two main categories describing the way data are routed between two points are _____ switching and _____ switching. packet, circuit (any order)

46. Review Which of the following establishes a permanent connection between the source and destination for the duration of the transfer? A. Circuit switching B. Packet switching A. Circuit switching

47. Review Which of the following allows packets to travel different routes to arrive at the destination? A. Circuit switching B. Packet switching B. Packet switching

48. Review 0010 0101 1110 The following is an example of the _____ data code representing decimal numbers 2, 5, and 14. BCD

49. Review The _____ character code uses eight bits to represent alphanumeric characters. A. ASCII B. BCD C. EBCDIC D. Unicode A. ASCII

50. Review The _____ character code uses 16 bits to represent individual characters. A. ASCII B. BCD C. EBCDIC D. Unicode D. Unicode