2. 5 Digital Encoding and Data Transmission

3. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. 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. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. 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. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Digital Signals  Measured in volts  After digital encoding, data placed on network mediadigital encoding  Encoding marked by voltage level and time period, which represents expected digital wave shapetime period  Unipolar digital signal Unipolar digital signal  Bipolar digital signal Bipolar digital signal

6. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Non-Return to Zero (NRZ)

7. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Manchester Encoding  Binary zero is represented by transition from zero to five volts in the midpoint of time period

8. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Data Transmission Modes  Synchronous transmission—Timing of digital signal important for decoding digital patterns Synchronous transmission  Asynchronous transmission—Beginning and end of data stream might be determined by: Asynchronous transmission  Series of ones or zeros  Long period of no digital transmission  Various other methods

9. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Data Packaging and Transmission  A segment gets packaged with extra information to ensure its deliverysegment  Encapsulation process Encapsulation  A packet travels across LANs only  A frame is encapsulated and can travel across the Internetframe

10. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Parity Check  Protects against corruption such as crosstalk, loose connections, interference  A Cyclic Redundancy Check (CRC) is more sophisticated error detector than parity checkCyclic Redundancy Check (CRC)

11. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Data Packaging Process

12. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Protocols  Connection-oriented communication—Connection is terminated after data is transferred Connection-oriented communication  Every frame must be verified  Results in slower data transfer speed  Connectionless communication—No need to terminate connection Connectionless communication  Results in faster transfer speed

13. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Connection-Oriented and Connectionless Communication

14. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Circuit and Packet Switching  Two main categories describing the way data are routed between two points  Circuit switching—Permanent Internet connection Circuit switching  Packet switching— Data broken down into packets with a source and destination address Packet switching

15. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Packet Switching

16. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. 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. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. ASCII  Earliest attempt to standardize data codes  Sometimes referred to as plain text files  Used by word processing programs

18. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. BCD

19. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. EBCDIC

20. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Unicode  Similar to ASCII  Over 65,000 possible characters  Used in bar codes for scanning merchandise  Used in Braille

21. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. 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. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. 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. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. UDP Frame Structure  Simple and compact protocol  First 16 bits of packet identify source portport  Second 16 bits identify destination port  Checksum uses one’s compliment to check for errors or corruptionone’s compliment  Last block of information contains actual data

24. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. UDP Frame

25. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Ethernet Frame Structure  Most common types are Ethernet II and IEEE 802.3  Generally compatible, but not guaranteed

26. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Ethernet Destination Address  When filled with all ones, the frame becomes a broadcast frame broadcast frame  Multicast frame is intended for a select number of computers Multicast frame

27. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. OSI Model and Data Encoding

28. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Application Layer  Where user interfaces with network operating system  Start and final destination of data communication

29. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Presentation Layer  Raw data is packaged into a universally agreed on form  Data byte order is also agreed on  Data encryption occurs Data encryption

30. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. 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. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Transport Layer  Responsible for flow of data to and from destination computer

32. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. 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 networksvirtual networks

33. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. 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. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Physical Layer  Concerned with media, hardware, and network topology

35. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. 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 D. 10GBaseT switch A. data linkC. data link B. physical D. data link Applied Networking

36. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.  American Standard Code for Information Interchange (ASCII)  A character code that uses eight bits to represent alphanumeric characters.  Asynchronous transmission  A type of transmission in which a digital signal is not synchronized with a reference signal.  Binary Coded Decimal (BCD)  A binary number format in which each number is represented as a four-digit binary code. Glossary

37. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.  Bipolar digital signal  A digital signal that fluctuates between a positive five-volt level and a negative five-volt level.  Broadcast frame  A frame intended for every computer on the network.  Circuit switching  A type of transmission which establishes a permanent connection between two points for the duration of the data transfer period. Glossary

38. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.  Connectionless communication  A type of communication in which data is transmitted to the destination without first establishing a connection.  Connection-oriented communication  A type of communication in which a connection is first established between the source and destination computers before data is transmitted. Glossary

39. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.  Cyclic Redundancy Check (CRC)  A sophisticated data integrity check that uses complicated mathematical algorithms to determine if one or more bits are corrupt.  Data encryption  The encoding of data based on a mathematical formula, which converts the original data symbol into another symbol.  Digital encoding  The conversion of data into a digital pattern acceptable to the network media. Glossary

40. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.  Encapsulation  The process of adding information to the segment that identifies such things as the source address, the destination address, the end of the segment, and the size of the segment.  Extended Binary Coded Decimal Interchange Code (EBCDIC)  An IBM character code similar to ASCII.  Frame  A packet that is encapsulated with information needed to travel the Internet. Glossary

41. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.  Hypertext Markup Language (HTML)  A programming language used to create Web pages.  Manchester encoding  An encoding scheme characterized by a digital pulse transitioning during the midpoint of the time period.  Multicast frame  A frame intended for a preselected number of computers, such as a specific workgroup. Glossary

42. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.  Non-Return to Zero (NRZ)  A digital signal that fluctuates between a high (positive) voltage level and a low (negative) voltage level and never returns to zero for any measurable period of time.  One’s compliment  A digital-based mathematical calculation used to check for errors or corruption. Glossary

43. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.  Packet switching  A type of transmission which does not use a permanent connection between two points for the duration of the data transfer period. Packets may travel different routes to the same destination.  Parity check  A method of verifying the integrity of transmitted data.  Port  A number that represents a logical connection and matches a service with a computer. Glossary

44. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.  Segment  Raw data that is divided into smaller units.  Synchronous transmission  A type of transmission in which a digital signal is synchronized with a reference signal to ensure proper timing.  Time period  The rate of recurrence of an expected signal level change. Glossary

45. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only.© Goodheart-Willcox Co., Inc.  Unicode  A character code that uses 16 bits to represent individual characters.  Unipolar digital signal  A digital signal that fluctuates between a positive five-volt and zero-volt level.  Virtual network  A logical network within a LAN. Glossary