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FE ELECTRICAL > Computer Network Systems Part 2 > Flashcards

Computer Network Systems Part 2 Flashcards

1
Q

serial interface

A

bits transmitted one at a time along a single line in a cable

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2
Q

parallel interface

A
  • all bits representing a character (typically seven, eight, or nine) transmitted at once
  • a separate line in the cable for each bit
  • additional line used as a strobe signal to carry a timing signal
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3
Q

universal serial bus (USB)

A

External bus standard that supports serial data transfer

  • can connect up to 127 devices
  • supports plug and play
  • allows hot plugging (also called hot swapping)
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4
Q

buffer

A
  • small amount of memory within a peripheral device

- peripheral sends status of buffer to computer by means of flow control (handshaking)

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5
Q

software flow control (handshaking)

A

technique for the computer to monitor the peripheral and begin sending more data as soon as the device is ready

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6
Q

peripheral signals

A

XOFF–> transmission off; buffer full, do not send data

XON –> transmission on; buffer is ready for more data

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7
Q

hardware handshaking

A

One or more lines between the computer and peripheral can be used for this.

  • serial printers require only two or three lines: data in, data out, and ground
  • further lines can be used for data terminal ready (DTR) or clear to send (CTS) handshaking
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8
Q

composite link

A
  • several peripherals along a single cable
  • data can be carried via multiplexers
  • achieved using frequency division or time division multiplexing
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9
Q

frequency division multiplexing (FDM)

A

available transmission band is divided into narrower bands, each used for a separate channel

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10
Q

time division multiplexing (TDM)

A
  • connection channel is operated at a much higher clock rate, and each peripheral shares equally in the available cycles
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11
Q

multiplexer (MUX)

A

Device that combines two or more signals for transmission over a single channel or line

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12
Q

demultiplexer (DMUX or DEMUX)

A

device used to separate two or more signals previously combined and transmitted over a single channel or line

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13
Q

random access (direct access) storage device (mass storage devices)

A 
permit access to individual records without having to read through entire file 
types include: 
- magnetic disk drives
- hard drives
- optical disk drives
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14
Q

hard drives

A
  • composed of several platters, each with one or more read/write heads
  • platters spin at high speeds (thousands of rpms)
  • organized into tracks, sectors, and cylinders
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15
Q

track

A

concentric storage areas

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16
Q

sector

A

pie-shaped subdivisions of each track

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17
Q

cylinder

A

consists of the same numbered track on all drive platters

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18
Q

optical disk drives

A
  • drive that uses laser light as part of the process of reading or writing data
  • -> read only (R/0)
  • -> read/write (R/W)
  • -> WORM (write once, read many)
  • -> CDR
  • -> DVD-R
  • -> CD-ROM
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19
Q

solid state drives (SSD)

A

Store data in arrays of interconnected, nonvolatile flash memory chips

  • faster data transfers than traditional disk drives
  • also more expensive
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20
Q

performance measures of a disk drive

A
  • memory size in MB (megabytes)
  • area density
  • -> a measure of the number of data bits stored per square inch of disk surface
  • -> the number of bits per track multiplied by the number of tracks per radial inch
  • average seek time
  • -> average time it takes to move from one location to a new location
  • track-to-track seek time
  • -> time required to move from one track to an adjacent track
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21
Q

latency (rotational delay)

A
  • time it takes to for a disk to spin a particular sector under the head for reading
  • latency is one-half the time to spin a full revolution
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22
Q

average access time

A
  • time required to move to a new sector and read the data
23
Q

access time

A
  • the sum of average latency and average seek time
24
Q

sequential access drives

A
  • computer has to read all information stored up to the point where data is located (for example, tape drives)
25
Q

indexed sequential format

A
  • format uses directory of files placed at start of tape

- tape can be quickly wound to location of information without having to read everything in between

26
Q

formats

A
  • nine track format
  • quarter inch cartridge (QIC)
  • digital audio tape (DAT)
27
Q

nine track format

A
  • tape divide into nine tracks running the length of the tape
  • width divided into frames (characters)
  • eight tracks used to record in ASCII or EBCDIC formats
  • ninth track used to record the parity bit
  • 1600 bpi (bits per inch) up to 9600 bpi typically used
28
Q

sequential access drives (continued)

A
  • frames are grouped into fixed length blocks separated by interblock gaps (IBG)
  • reflective spots for photoelectric detection can be used to indicate the beginning and end of magnetic tapes, called load point and end-of-file (EOF) markers.
  • Magnetic tape is sometimes used to back up hard disks
  • Streaming tape is continuously running while data is written or read
29
Q

batch processing

A
  • all jobs of a particular type held and batched together for subsequent processing
30
Q

real-time processing

A

a program runs when submitted, often with user interaction during processing

31
Q

virtual machine

A

has computer memory allocated for partitioned among several users running applications simultaneously

  • CPU and main memory must be large enought
  • Each user appears to have his or her own machine
32
Q

multitasking, multiprogramming, time sharing (swapping)

A

user take turns using the entire computer main memory for a certain length of time (less than a second)

  • under the control of operating system
  • at end of time period, all active memory is written to private area
  • memory for the next user is loaded
  • swapping is so quick that all users are able to accomplish useful work in real time
33
Q

network

A

connected arrangement of physically separated computers and components

34
Q

networking

A 
the use of communication links to connect these computer 
transmission line may be 
- standard metal conductor
- fiber optic cable 
- infrared connection
- microwave connection
- some other communication path
35
Q

wide are network (WAN)

A

centrally located main computer interacts with, and is fed by, smaller computers located elsewhere

  • larger geographic area, used for the internet, government facilities, large corporations
  • slower than LAN, about 150 Mbps
36
Q

local area network (LAN)

A

many computers linked together in order to share storage and printing resources

  • smaller are than WAN, used for homes, offices, schools
  • up to 100 Gbps
37
Q

download, upload

A

referenced from user’s perspective

  • download a file: user receives a file
  • upload a file: user sends a file

Downstream and upstream are also referenced from the user’s perspective

  • user sends data upstream to the host
  • user receives data downstream from the host
38
Q

asymmetrical digital subscriber line (ADSL)

A

refers to direction-driven transmission speeds, typically lower for uploading than for downloading

39
Q

circuit switching

A
  • uses a dedicated path between sending and receiving units
40
Q

packet switching

A

transmits a message in separate pieces (packets) over multiple paths through control computers (nodes)

  • packets of data treated independently
  • can be routed through different nodes
  • can arrive at the end in any order
  • encoding allows data to be assembled into proper sequence
41
Q

simplex communication

A

data transmission in one direction only

42
Q

half-duplex communication

A

data transmission in both directions but only one direction at a time

43
Q

duplex or full-duplex communication

A

data transmission in both direction simultaneously

44
Q

asynchronous transmission

A

each character preceded and followed by special signals

  • start and stop bits
  • every 8-bit character is transmitted as 10 bits
  • character transmission rate is 1/10 of transmission speed in bps
  • possible to distinguish the beginning and end of each character within the bit stream
45
Q

synchronous transmission

A

transmits blocks of data continuously without pause requiring a built-in clock to maintain synchronization

  • synchronous transmission preceded by and interwoven with special clock-synchronizing characters
  • separation of a bit stream into individual characters performed by counting bits from the start of the previous character
  • about 20% faster than asynchronous communication
46
Q

communication lines

A

narrow band
- supports a single channel

voice grade
- supports frequencies between 300 Hz and 3300 Hz

wideband
- supports highest transfer rates

47
Q

errors in transmission

A
  • can occur at the rate of 1 in 10,000 over voice-grade lines
  • communication protocols and transmission standards are methods to ensure accuracy
48
Q

loop or echo checking

A

each block of data is sent back to the sender and if the characters in the block do not match, they are re-sent

49
Q

check digit or block check character

A

derived from the remainder after dividing all serialized bits in transmission block by a predetermined binary number

50
Q

network topology

A

physical or logical arrangement of the components of a computer system

51
Q

protocol

A

operational and communications rules followed by computers and other devices

  • standards
  • recommended standards
52
Q

standards organizations

A

international organization for standardization (ISO)

American National Standards Institute (ANSI)

53
Q

internet

A

consists of numerous interconnected computers, servers, nodes, and networks using common communication protocols

  • transmission control protocol/ internet protocol (TCP/IP)
  • file transfers protocols (FTP)
  • graphical user interfaces (GUI)
  • hypertext data structures and hypertext markup language (HTML)
54
Q

domain names

A

device addresses used to allow the movement of information between networks and hosts of the internet

top level domain names; .com, .edu, .gov, .org, .net

FE ELECTRICAL (17 decks)

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