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Network > Network Communications Method 2 > Flashcards

Network Communications Method 2 Flashcards

0
Q

What makes a data transfer instantaneous

A

Data immediately converted into a network compatible format and transmitted without being stored either in main memory or on a disk

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1
Q

What is data transmission

A

The exchange of data among different devices through a network

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2
Q

Digital data transmission uses

A

Uses voltage difference to represent 1’s & 0’s in data. Not modulated over a carrier. Each bit takes a predefined time to transmit. the sender and receiver synchronize their clocks by transmitting a bit pattern or by monitoring for the reception of the first bit

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3
Q

On-keying or Manchester encoding converts

A

Converts data into a digital waveform

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4
Q

Describe on-keying

A

A digital data transmission encoding scheme in which a change in voltage from one state to another within a predetermined interval is symbolized by a 1. No voltage transmission is symbolized by 0. The receiver synchronizes its clock with the sender by watching for the 1’s

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5
Q

What problems can arise when using on-keying & off-keying data transmission

A

When long sequence of 1’s and 0’s must be sent problems can arise because the receiver is synchronizing its clocks to 1’s received. They may not be able to synchronize over long intervals. Making its clock out of sync and leading to data corruption. Used over serial ports. Low speed digital data transmission

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6
Q

Manchester encoding is

A

Used over the ethernet. high speed digital data connections. Transitions from positive to ground represents a binary 0
A negative to positive voltage transmission in the middle of the bit period is a binary 1

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7
Q

Unicode transmission is a method for

A

Data transfer from a source address to a destination address. Main mode of transportation on LANs and the Internet

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8
Q

List some unicast applications

A

HTTP hyper-text transfer protocol
SMTP simple mail transfer protocol
FTP file transfer protocol

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9
Q

Broadcast transmission is

A

A transmission method where data is sent from a source node to all other nodes on a network. Checks for the availability of a particular service on the network

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10
Q

Multi-cast transmission is

Give an example

A

Transmission method where data is sent from a server to specific nodes that are predefined as members of the group
Ex video server transmitting tv signals

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11
Q

With serial data transmission the transmission of bits occurs as

A

On clock cycle across a single transmission medium. Does not use DC pulses for transmission

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12
Q

List some devices that connect over a serial transmission port

A

Keyboard
Mice
Modems

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13
Q

The receiver of an analog signal delineates between bytes in a stream of data using either

A

Synchronous communication. A byte is sent after a standard time interval

Or

Asynchronous. A sender inserts special start stop bit patterns between each byte of data.

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14
Q

With parallel data transmission how does transmission take place

A

Transmission if multiple bits takes place by using g multiple lines many bits transferred per clock cycle. Commonly used in parallel port connecting printers and scanners

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15
Q

In baseband transmission

A

Digital signals are sent via DC direct current. Pulses over a single unmultiplexed signal channel. Cannot send and receive simultaneously

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16
Q

In broadband data transmission

A

Uses analog signal to send data over a transmission medium using the complete bandwidth of the medium. Signals travels unidirectionally.

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17
Q

Broadband over power lines (BPL)

A

Allows broadband data transmission over domestic power lines. Has potential to cause interference with other data signals. Raises security issues because easily detected and intercepted

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18
Q

The media access method determines

A

Determines whether or not a particular node can transmit data in the network at a given time.

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19
Q

Name the two media access methods two categories

A

Contention based on competitive media access. The nodes themselves negotiate for media access time
Controlled or deterministic media access. A central device controls when and for how long each node can transmit.

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20
Q

Compare the media access categories.

A

Deterministic or control based are beneficial when a network access is time critical. Ensures that a single node cannot saturate the media

Contention based media access systems are simpler to set up and administer. Timeliness not guaranteed

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21
Q

What is multiplexing.

A

A controlled media access method. A central device combined signals from multiple nodes and transmits the combined signal across a medium

22
Q

Two ways signals can be multiplexed

A

Using TDM time division multiplexing. Or
FDM frequency division multiplexing.
Relies on a central device called a multiplexer or mux to manage multiplexing from the sending end.
At the receiving end a demultiplexer or demux separates the signals.

23
Q

In TDM time division multiplexing a communication channel is

A

Divided into discrete time slots. Each node on a network is assigned a time slot.
Category of media access method

24
Q

In FDM frequency division multiplexing

A

Data from multiple nodes is sent over multiple frequencies using a network medium. Multiple broadband signals can be combined and sent over a single medium
Category of media access method

25
Q

Polling is a controlled media access method in which

Give an example

A

A central device contacts each node to check I’d it has data to transmit
Ex is demand priority. The technique in which nodes signal the state either ready to transmit or idle to an intelligent hub which grants permissions to transmit

26
Q

What is CSMA/CD

A

Carrier Sense Multiple Access/Collision Detection

A contention based media access method used in Ethernet LANs to provide collision free data transfer

27
Q

Ethernet formalized IEEE standard

A

802.3 standard

28
Q

List the five steps involved in CSMA/CD process

A

Carrier Sense Multiple Access/Collision Detection

  1. A node has data to transmit
  2. Node checks network by polling
  3. Node transmits data waits for ACK
  4. Node checks packet size for any collisions
  5. Waits if collision occurs both transmitting devices wait for a random backoff period before retransmitting. Repeats until successful
29
Q

PoE standard

A

Power over Ethernet. 802.3af
Specifies a method for supplying electrical power over Ethernet connections. Specifies two device types
PSE powered sourcing equipment. Provides the power
PD powered devices. Those that receive the power from the PSE
Requires cat 5 cabling or higher

30
Q

What is CSMA/CA

A

Carrier Sense Multiple Access/Collision Avoidance
A contention based media access method primarily used in 802.11 wireless LANs
Nodes can transmit whenever they have data to send

31
Q

List the six steps for CSMA/CA

A

Carrier Sense Multiple Access/ Collision Avoidance

  1. Node has data to send
  2. Node checks network by polling
  3. The node transmits a jam signal advertising its intent to transmit data
  4. Node waits until all nodes receive jam signal
  5. Node transmits data
  6. Node monitors media for jam signal from other nodes
32
Q

Contention domain is

A

Also called a collision domain. Is a contention based network on which a group of nodes are allowed to compete with each other for media access. Results in collisions

33
Q

Broadcast domain

A

A logical area in a computer network where any node connected to the network can directly transmit to any other node in the domain without having to go through a central routing device

34
Q

A broadcast domain refers to

A

The set of devices that received a broadcast data frame originating from any device with A LAN subnet. A layer two switch config defines the boundaries of the domain while a layer three switch or router is required to connect them

35
Q

Broadcast domain vs. collision domain

A

Main difference is size of the domains.
Multiple collision domains can make up a broadcast domain but a broadcast domain associates itself with only a single collision domain. Also differ in the way they affect performance on a network. Collision domain increase in traffic results on higher probability of collisions on the network

36
Q

What is a signal

A

Data transmitted as electromagnetic pulses across a network medium

37
Q

An analog signal carries

A

Info as continuous waves of electromagnetic or optical enemy

38
Q

Electrical current commonly generates analog signals the intensity is measure in

A

Volts

39
Q

An analog signal oscillates between

A

Maximum & minimum values overtime and can take any value between those limits

40
Q

Analog signal characteristics

A

Amplitude. Is one half the overall distance from the peak to the trough of the wave
Cycle. One complete oscillation
Frequency. The number of complete cycles per second in a wave. Measured in hertz
Phase. Where a wave cycle begins in relation to a fixed point.
Wavelength. Distance between two successive crests or troughs in a waveform.

41
Q

An oscilloscope is

A

A device that plots the amplitude of an analog signal as a function of time. Displays as sine waves

42
Q

A digital signal can have

A

Combinations of only two values. 0 & 1 represents the presence and absence of s signal

43
Q

Every pulse in a digital signal represents

A

One binary digit or bit

44
Q

Eight bits constitutes

A

One byte

45
Q

Digital data is represented as

A

Binary 1s & 0s or logical states

46
Q

Units of digital data

A

Bit. Single 1 or 0
Nibble. Four bits
Byte. Eight bits
Word. 16 bit, 32 bit or 64 bit

47
Q

Explain analog signal modulation demodulation

A

Analog signals transmit at low frequencies. To overcome info loss and interference the analog signal is superimposed over the high frequency signal called a carrier using a modulator. When this new modulated signal reaches its destination the receiver uses demodulation to remove the carrier signal from the data signal

48
Q

A codec is

A

Software or hardware that encodes digital data to and from the analog format. Modem is a type.

49
Q

DAC & ADC

A

Digital to analog codec. Specific chip that performs the digital to analog conversion
Analog to digital codec. Chip that performs analog to digital conversion

50
Q

Digital signal modulation & demodulation

A

Digital data cannot be directly transmitted through a medium over a long distance. The digital data must be represented in the form of an analog signal for transmission of data between device ie modulation. For demodulation the receiving digital device compares the modulated analog signal with the preset frequency or amplitude of the signal and uses the comparison results to reconstruct the digital data

51
Q

A modem is a device that

A

Modulates and demodulates data to an analog signal sent over telephone lines

52
Q

Digital signal modulation techniques

A

ASK amplitude shift key. Changes the amplitude of the analog signal depending on the logical state of digital data.
FSK frequency shift key. Changes the frequency of the analog signal depending on the logical state of digital data.
BPSK binary phase shift key. Changes the phase of the analog signal depending on the logical state of digital data.
QPSK quadrature phase shift key. Changes the phase of the analog signal to represent two logical states at a time. 00,01,10,11
QAM quadrature amplitude modulation. Combines both amplitude and phase shift key modulation. This helps represent more than two logical states at a time

53
Q

Digital signal reference methods

A

Need a reference method to determine the conditions of the signal. Demodulation using one of two methods
Differential. A modem compares modulated and demodulated digital signals. The difference in output is result.
Single ended. The modem compares the signal on one line to ground. Difference from ground is output.

Network (15 decks)

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