Transcript Chapter 5 - Goodheart

5
Digital Encoding and
Data Transmission
Objectives
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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.
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Objectives
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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.
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Digital Signals
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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
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Non-Return to Zero (NRZ)
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Manchester Encoding
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Binary zero is represented by transition from zero
to five volts in the midpoint of time period
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Data Transmission Modes
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Synchronous transmission—Timing of digital
signal important for decoding digital patterns
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Asynchronous transmission—Beginning and end
of data stream might be determined by:
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Series of ones or zeros
Long period of no digital transmission
Various other methods
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Data Packaging and Transmission
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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
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Parity Check
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Protects against corruption such as crosstalk,
loose connections, interference
A Cyclic Redundancy Check (CRC) is more
sophisticated error detector than parity check
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Data Packaging Process
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Protocols
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Connection-oriented communication—Connection
is terminated after data is transferred
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Every frame must be verified
Results in slower data transfer speed
Connectionless communication—No need to
terminate connection
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Results in faster transfer speed
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Connection-Oriented and
Connectionless Communication
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Circuit and Packet Switching
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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
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Packet Switching
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Data Codes
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Represent the written word
Communicating systems must use the same data
code
Data code conversion must occur for data
exchange to take place
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ASCII
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Earliest attempt to standardize data codes
Sometimes referred to as plain text files
Used by word processing programs
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BCD
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EBCDIC
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Unicode
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Similar to ASCII
Over 65,000 possible characters
Used in bar codes for scanning merchandise
Used in Braille
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Hypertext Markup Language (HTML)
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On web page, color code is translated into color
the code represents
Web browsers interpret code and create shade of
color indicated
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Protocol Frame Structures
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The exact structure used is determined by the:
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Purpose of communication
Type of network architecture
Use of specialized equipment and media during
transfer
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UDP Frame Structure
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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
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UDP Frame
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Ethernet Frame Structure
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Most common types are Ethernet II and IEEE
802.3
Generally compatible, but not guaranteed
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Ethernet Destination Address
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When filled with all ones, the frame becomes a
broadcast frame
Multicast frame is intended for a select number of
computers
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OSI Model and Data Encoding
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Application Layer
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Where user interfaces with network operating
system
Start and final destination of data communication
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Presentation Layer
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Raw data is packaged into a universally agreed
on form
Data byte order is also agreed on
Data encryption occurs
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Session Layer
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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
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Transport Layer
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Responsible for flow of data to and from
destination computer
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Network Layer
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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
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Data Link Layer
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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
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Physical Layer
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Concerned with media, hardware, and network
topology
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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
D. 10GBaseT switch
A. data link
B. physical
C. data link
D. data link
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Review
The signal shown is an example of a _____
digital signal.
A. bipolar
B. unipolar
B. unipolar
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Review
The signal shown is an example of a _____
digital signal.
A. bipolar
B. unipolar
A. bipolar
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Review
The mode of data transmission in which the
digital signal synchronized with a reference
signal is referred to as _____.
synchronous
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Review
The mode of data transmission in which the
digital signal is not synchronized with a
reference signal is referred to as _____.
asynchronous
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Review
To perform a(n) _____, the last bit position in
an 8-bit data transmission can be used for
the parity code.
parity check
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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
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Review
A(n) _____ uses complicated mathematical
algorithms to determine if one if more bits are
corrupt.
Cyclic Redundancy Check (CRC)
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Review
Which mode of communication terminates
the session when all data has been
transferred?
A. Connection-oriented
B. Connectionless
A. Connection-oriented
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Review
Which mode of communication does not
establish a connection before transmitting
data?
A. Connection-orientated
B. Connectionless
B. Connectionless
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Review
Two main categories describing the way data
are routed between two points are _____
switching and _____ switching.
packet, circuit (any order)
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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
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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
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Review
The following is an example of the _____
data code representing decimal numbers 2,
5, and 14.
0010 0101 1110
BCD
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Review
The _____ character code uses eight bits to
represent alphanumeric characters.
A. ASCII
B. BCD
C. EBCDIC
D. Unicode
A. ASCII
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Review
The _____ character code uses 16 bits to
represent individual characters.
A. ASCII
B. BCD
C. EBCDIC
D. Unicode
D. Unicode
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Review
A(n) _____ is a logical connection that
matches a service with a computer.
port
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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
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Review
The _____ frame type includes a Start Frame
Delimiter (SFD).
A. Ethernet II
B. IEEE 802.3
B. IEEE 802.3
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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
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Review
The _____ frame type was developed before
the release of the IEEE 802.3 CSMA/CD
standard.
Ethernet II
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Review
Which layer of the OSI model is responsible
for the flow of data to and from destination
computer?
Transport
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Review
Which layer of the OSI model is concerned
with media, hardware, and network topology?
Physical
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Review
Which layer of the OSI mode provides the
means of routing data packets across a WAN
or MAN?
Network
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Review
Which layer of the OSI model negotiates
decisions about how data flow is controlled
and how session ends?
Session
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Glossary
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American Standard Code for Information
Interchange (ASCII)
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Asynchronous transmission
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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)
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A binary number format in which each number is
represented as a four-digit binary code.
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Glossary
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Bipolar digital signal
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Broadcast frame
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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
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A type of transmission which establishes a
permanent connection between two points for the
duration of the data transfer period.
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Glossary
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Connectionless communication
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A type of communication in which data is transmitted
to the destination without first establishing a
connection.
Connection-oriented communication
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A type of communication in which a connection is
first established between the source and destination
computers before data is transmitted.
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Glossary
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Cyclic Redundancy Check (CRC)
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Data encryption
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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
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The conversion of data into a digital pattern
acceptable to the network media.
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Glossary
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Encapsulation
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Extended Binary Coded Decimal Interchange
Code (EBCDIC)
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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
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A packet that is encapsulated with information
needed to travel the Internet.
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Glossary
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Hypertext Markup Language (HTML)
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Manchester encoding
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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
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A frame intended for a preselected number of
computers, such as a specific workgroup.
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Glossary
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Non-Return to Zero (NRZ)
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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.
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Glossary
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Packet switching
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Parity check
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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
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A number that represents a logical connection and
matches a service with a computer.
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Glossary
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Segment
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Synchronous transmission
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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
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The rate of recurrence of an expected signal level
change.
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Glossary
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Unicode
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Unipolar digital signal
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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
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A logical network within a LAN.
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