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DATA COMMS > Part 4 > Flashcards

Part 4 Flashcards

1
Q

Eliminates redundant bits, thereby reducing the bit rate with no effect on signal quality.

A

Lossless compression

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2
Q

Compromises signal quality in order to reduce the bit rate. For voice transmissions, vocoders are often used to achieve great reductions in bit rate.

A

Lossy compression

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3
Q

It is a lossless compression technique, in which each time a zero is encountered in the input data, two values are written to the output file.

A

Run Length Encoding

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4
Q

It is a lossless data compression technique, the idea of the compression is to assign frequently used character fewer bits, and seldom used characters more bits.

A

Huffman Encoding

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5
Q

A more sophisticated version of the Huffman encoding; in this scheme, sequences of characters are represented by individual codes, according to their probability of occurrence, and this has the advantage of better data compression (5 to 10%).

A

Arithmetic Encoding

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6
Q

Term that refers to several techniques that store data as the difference between successive samples or characters, rather than directly storing the samples themselves.

A

Delta

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7
Q

The first value in the delta encoded file is the same as the first value in the original data; all values in the encoded file are equal to the difference (delta) between the corresponding value in the input file, and the previous value in the input file.

A

Delta Encoding

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8
Q

It is a lossless data compression and the foremost technique for general purpose data compression due to its simplicity and versatility

A

LZW Compression

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9
Q

It is always used in GIF image files, and offered as an option in TIFF and PostScript

A

LZW Compression

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10
Q

It uses a code table; the encoded data consists entirely of 12- bit codes, each referring to one entries in the code table; uncompression is achieved by taking each code from the compressed file, and translating it through the code table to find what character it represents

A

LZW Compression

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11
Q

GIF
JPEG
MPEG

A

Graphics Interchanged Format
Joint Photographers Experts
Moving Pictures Expert Group

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12
Q

It works best on natural images (scenes) and it is a lossy format, which means that the decompressed image is not quite the same as the original. It saves space by throwing away parts of the image; it achieves much greater compression than is possible with lossless methods like GIF.

A

JPEG Compression

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13
Q

It is intended for compressing images that will be looked by humans, not machines; small errors introduced by this compression are virtually undetectable by the naked eye.

A

JPEG Compression

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14
Q

It is a compression standard for digital video sequences, such as in computer video and digital television networks; it also provides for the compression of the sound track associated with the video.

A

MPEG Compression

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15
Q

Means that individual frames making up the video sequence are encoded as if they were originally still images; this compression is performed using the
JPEG standard.

A

Within-the-frame compression

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16
Q

Is an initial video and audio compression standard, later used as the standard for video CD, and includes the popular layer 3 (MP3) audio compression format.

A

MPEG-1

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17
Q

Is a transport, video, and audio standard for broadcast-quality television

A

MPEG-2

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18
Q

Was originally assigned for HDTV, but abandoned when it was discovered that MPEG-2 (with extensions) was sufficient for HDTV. Not mp3

A

MPEG-3

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19
Q

Expands MPEG-1 to support video/audio objects, 3D content, low bit rate encoding and support for digital rights management.

A

MPEG-4

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20
Q

Is the standard for description and search of audio and visual content.

A

MPEG-7

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21
Q

Is the multimedia framework.

A

MPEG-21

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22
Q

It is a general term that describes the interface equipment used at the stations to adapt the digital signals from the computers and terminals to a form more suitable for transmission.

A

Data Terminal Equipment (DTE)

23
Q

It can be virtually any binary digital device that generates transmits, receives, or interprets data messages (i.e., it is where information originates or terminates). (desktops, laptops, printers, routers, IP phones, etc.)

A

Data Terminal Equipment (DTE)

24
Q

It is also known as the channel or medium, and it is the transmission facility that connects two points together (i.e., it is any form of transmission media used to transfer data from local terminal to a remote location).

A

Transmission Path

25
Q

Enhanced category 5 twisted pair cables used to connect dissimilar devices such as DCE to DTE and DTE to DCE.

A

Straight-Through Cable

26
Q

Enhanced category 5 twisted pair cables used to connect similar devices such as DCE to DCE and DTE to DTE.

A

Crossover Cable

27
Q

It is the general term that describes the equipment that converts the digital signals to analog signals and interfaces the data terminal equipment to the analog transmission system.
(LAN switches, hubs, modems, multiplexers, etc.)

A

Data Communications Equipment (DCE)

28
Q

It is a device that carries out a modulation function on the transmit side of a circuit and a demodulation function on the reverse side.

A

Modem

29
Q

It is a device used to convert serial digital data from a transmitting terminal to a signal suitable for transmission over a telephone channel.

A

Modem

30
Q

The most commonly used modulation techniques in modems are?

A

FSK (frequency-shift keying), PSK (phase shift keying), and QAM (quadrature amplitude modulation).

31
Q

It is also known as, baseband modem or line drivers. It can be use up to 40 ft or 12 m distance.

A

Short-Range Modem/short- haul modem

32
Q

It is also known as analog modem or long-haul modem. It can be use up to 4000 ft or 1200 m distance.

A

Long-Range Modem

33
Q

Is a modem technology that uses existing twisted pair telephone lines to transport high bandwidth data, such as multimedia and video, to service subscribers.

A

DSL (digital subscriber line)

34
Q

It is a device that performs the task of combining numbers of channels into a single communication link.

A

Multiplexer

35
Q

It is a multiplexer with storage buffer and a minicomputer or microcomputer processor, and it may act to store and forward traffic and is used to hold program logic.

A

Concentrator

36
Q

It is a two-port device which operates at the physical layer, and its job is to regenerate the signal over the same network before the signal becomes too weak or corrupted so as to extend the length to which the signal can be transmitted over the same network. They do no amplify.

A

Repeater

37
Q

It is basically a multiport repeater which connects multiple wires coming from different branches.
It cannot filter data, so data packets are sent to all connected devices

A

Hub

38
Q

It also does not have intelligence to find out best path for data packets which leads to inefficiencies and wastage.

A

Hub

39
Q

It is a two-port device (single input and single output port) which operates at data link layer.
It is a repeater, with add on functionality of filtering content by reading the MAC addresses of source and destination, and it is also used for interconnecting two LANs working on the same protocol.

A

Bridge

40
Q

It is a multiport bridge which operates at data link layer with a buffer and a design that can boost its efficiency (large number of ports imply less traffic) and performance.

A

Switch

41
Q

It can perform error checking before forwarding data that makes it very efficient as it does not forward packets that have errors and forward good packets selectively to correct port only (i.e., divides collision domain of hosts, but broadcast domain remains same).

A

Bridge

42
Q

It is a device like a switch, but operates in the network layer, that routes data packets based on their IP addresses.

A

Router

43
Q

It normally connects LANs and WANs together and have a dynamically updating routing table based on which they make decisions on routing the data packets, it also divide broadcast domains of hosts connected through it.

A

Router

44
Q

It is also known as protocol converters and can operate at any network layer.
It is a passage to connect two networks together that may work upon different networking models

A

Gateway

45
Q

Is used for asynchronous transmission of data between the DTE and the DCE

A

UART (universal asynchronous receiver/transmitter)

46
Q

Is used for synchronous transmission of data between the DTE and the DCE.

A

USRT (universal synchronous receiver/transmitter)

47
Q

It is a transparent switch that is used for making a standard telephone call on public telephone network (the call is established, information is transferred, and then the call is terminated).

A

Circuit Switching

48
Q

Its advantages includes; mature technology; near real-time connectivity; excellent inquiry and response; and leased service attractive.
Its disadvantages includes; high cost of switch; and lower system utilization particularly link utilization.

A

Circuit Switching

49
Q

It is a form of store-and-forward network in which data including source and destination identification codes are transmitted into the network and stored in a switch (each switch in the network has message storage capabilities, thus blocking cannot occur).

A

Message Switching

50
Q

Its advantages includes; efficient trunk utilization; and cost- effective for low volume leased service.
Its disadvantages includes; delivery delay may be a problem; not viable for inquiry and response; and problematical survivability.

A

Message Switching

51
Q

It is also known as a hold-and-forward network (a packet can be held in memory at a switch for a short period of time) in which the data are divided into smaller segments known as packets prior to transmission through the network.

A

Packet Switching

52
Q

Its advantages includes; efficiency approaches near-real time connectivity; highly reliable, survivable; and low traffic volume attractive for leased service.
Its disadvantages includes; expensive multiple route and node network; intensive processing; and large traffic volume justifies private ownership.

A

Packet Switching

53
Q

Is a switch that does more than simply transfer the data from source to the destination. It can store data or change its format and bit rate, the convert the data back to their original form or an entirely different form at the received end.

A

Transactional switch

54
Q

Is a switch that does nothing more than interconnect the source and destination terminal equipment. A circuit adds no value to the circuit.

A

Transparent switch

DATA COMMS (6 decks)

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