5 Digital Encoding and Data Transmission Permission granted to reproduce for educational use only.©...

5Digital Encoding and Data Transmission

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.



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.



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



Non-Return to Zero (NRZ)



Manchester Encoding

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



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



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



Parity Check

Protects against corruption such as crosstalk, loose connections, interference

A Cyclic Redundancy Check (CRC) is more sophisticated error detector than parity check



Data Packaging Process



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



Connection-Oriented and Connectionless Communication



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



Packet Switching



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



ASCII

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



BCD



EBCDIC



Unicode

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



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



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



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



UDP Frame



Ethernet Frame Structure

Most common types are Ethernet II and IEEE 802.3

Generally compatible, but not guaranteed



Ethernet Destination Address

When filled with all ones, the frame becomes a broadcast frame

Multicast frame is intended for a select number of computers



OSI Model and Data Encoding



Application Layer

Where user interfaces with network operating system

Start and final destination of data communication



Presentation Layer

Raw data is packaged into a universally agreed on form

Data byte order is also agreed on Data encryption occurs



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



Transport Layer

Responsible for flow of data to and from destination computer



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



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



Physical Layer

Concerned with media, hardware, and network topology



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 link C. data link

B. physical D. data link

Applied Networking



The signal shown is an example of a _____ digital signal.

A. bipolar

B. unipolar

B. unipolar

Review



The signal shown is an example of a _____ digital signal.

A. bipolar

B. unipolar

A. bipolar

Review



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

synchronous

Review



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

asynchronous

Review



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

parity check

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

Review



A(n) _____ uses complicated mathematical algorithms to determine if one if more bits are corrupt.

Cyclic Redundancy Check (CRC)

Review



Which mode of communication terminates the session when all data has been transferred?

A. Connection-oriented

B. Connectionless

A. Connection-oriented

Review



Which mode of communication does not establish a connection before transmitting data?

A. Connection-orientated

B. Connectionless

B. Connectionless

Review



Two main categories describing the way data are routed between two points are _____ switching and _____ switching.

packet, circuit (any order)

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


Review



Which of the following allows packets to travel different routes to arrive at the destination?


B. Packet switching

B. Packet switching

Review



The following is an example of the _____ data code representing decimal numbers 2, 5, and 14.

BCD

Review

0010 0101 1110



The _____ character code uses eight bits to represent alphanumeric characters.

A. ASCII

B. BCD

C. EBCDIC

D. Unicode

A. ASCII

Review



The _____ character code uses 16 bits to represent individual characters.

A. ASCII

B. BCD

C. EBCDIC

D. Unicode

D. Unicode

Review



A(n) _____ is a logical connection that matches a service with a computer.

port

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

Review



The _____ frame type includes a Start Frame Delimiter (SFD).

A. Ethernet II

B. IEEE 802.3

B. IEEE 802.3

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

Review



The _____ frame type was developed before the release of the IEEE 802.3 CSMA/CD standard.

Ethernet II

Review



Which layer of the OSI model is responsible for the flow of data to and from destination computer?

Transport

Review



Which layer of the OSI model is concerned with media, hardware, and network topology?

Physical

Review



Which layer of the OSI mode provides the means of routing data packets across a WAN or MAN?

Network

Review



Which layer of the OSI model negotiates decisions about how data flow is controlled and how session ends?

Session

Review


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


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




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




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




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




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




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




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




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




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




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

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