5 Digital Encoding and Data Transmission Objectives q

5 Digital Encoding and Data Transmission

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

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

Digital Signals q q q 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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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

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

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

Data Packaging and Transmission q q 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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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

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

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

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

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

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

Data Codes q q q Represent the written word Communicating systems must use the same data code Data code conversion must occur for data exchange to take place © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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

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

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

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

Hypertext Markup Language (HTML) q q On web page, color code is translated into color the code represents Web browsers interpret code and create shade of color indicated © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Protocol Frame Structures q The exact structure used is determined by the: Purpose of communication q Type of network architecture q Use of specialized equipment and media during transfer q © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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

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

Ethernet Frame Structure q q Most common types are Ethernet II and IEEE 802. 3 Generally compatible, but not guaranteed © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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

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

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

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

Session Layer q q q 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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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

Network Layer q q 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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Data Link Layer q q q 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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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

Applied Networking You are installing a new network that adheres to the IEEE 10 GBase. T standard. To which layers of the OSI model do the following aspects of the IEEE 10 GBase. T standard relate? A. 10 GBase. T network card B. Cat 6 a or 6 cable C. CSMA/CD media access method D. 10 GBase. T switch A. data link B. physical C. data link D. data link © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review The signal shown is an example of a _____ digital signal. A. bipolar B. unipolar © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review The signal shown is an example of a _____ digital signal. A. bipolar B. unipolar A. bipolar © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review The mode of data transmission in which the digital signal synchronized with a reference signal is referred to as _____. synchronous © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review The mode of data transmission in which the digital signal is not synchronized with a reference signal is referred to as _____. asynchronous © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review To perform a(n) _____, the last bit position in an 8 -bit data transmission can be used for the parity code. parity check © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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

Review A(n) _____ uses complicated mathematical algorithms to determine if one if more bits are corrupt. Cyclic Redundancy Check (CRC) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review Which mode of communication terminates the session when all data has been transferred? A. Connection-oriented B. Connectionless A. Connection-oriented © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review Which mode of communication does not establish a connection before transmitting data? A. Connection-orientated B. Connectionless © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review Two main categories describing the way data are routed between two points are _____ switching and _____ switching. packet, circuit (any order) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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

Review Which of the following allows packets to travel different routes to arrive at the destination? A. Circuit switching B. Packet switching © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review The following is an example of the _____ data code representing decimal numbers 2, 5, and 14. 0010 0101 1110 BCD © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review The _____ character code uses eight bits to represent alphanumeric characters. A. ASCII B. BCD C. EBCDIC D. Unicode A. ASCII © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review The _____ character code uses 16 bits to represent individual characters. A. ASCII B. BCD C. EBCDIC D. Unicode © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review A(n) _____ is a logical connection that matches a service with a computer. port © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review The _____ of a UDP frame uses the one’s compliment to check for errors or corruption. A. checksum B. destination port C. length D. source port A. checksum © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review The _____ frame type includes a Start Frame Delimiter (SFD). A. Ethernet II B. IEEE 802. 3 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review The _____ indicates the start of the frame with a one-byte binary pattern. A. preamble B. length C. SFD D. frame check sequence C. SFD © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review The _____ frame type was developed before the release of the IEEE 802. 3 CSMA/CD standard. Ethernet II © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review Which layer of the OSI model is responsible for the flow of data to and from destination computer? Transport © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review Which layer of the OSI model is concerned with media, hardware, and network topology? Physical © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review Which layer of the OSI mode provides the means of routing data packets across a WAN or MAN? Network © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review Which layer of the OSI model negotiates decisions about how data flow is controlled and how session ends? Session © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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

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

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

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

Glossary q Encapsulation q q Extended Binary Coded Decimal Interchange Code (EBCDIC) q q 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. An IBM character code similar to ASCII. Frame q A packet that is encapsulated with information needed to travel the Internet. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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

Glossary q Non-Return to Zero (NRZ) q q 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 q A digital-based mathematical calculation used to check for errors or corruption. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Glossary q Packet switching q q Parity check q q 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. A method of verifying the integrity of transmitted data. Port q A number that represents a logical connection and matches a service with a computer. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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

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