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Comp sci > Chap 2.1 - data transmission > Flashcards

Chap 2.1 - data transmission Flashcards

1
Q

define data

A

info. translated for efficient transmission

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2
Q

define transmission

A

-movement of data from 1 device to another

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3
Q

define processing

A

-generating meaningful info.

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4
Q

how is a text sent

A

-text
-converted into binary
-arranged into data packets / datagram
-router
-internet
-person

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5
Q

define data packet

A

-data split into smaller bytes for transmission over a network
-contains header, payload, trailer

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6
Q

standard size of data packets

A

-64 KiB

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7
Q

what happens if data packet is small

A

-add 0’s

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8
Q

are data packets unlimited

A

yes

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9
Q

data packet structure for packet switching

A

-header
-payload
-trailer

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10
Q

what is in a header

A

-IP address of source device
-IP address of destination device
-sequence of packet (packet no.)
-size of packet in bytes
-total no. packets
-IP of router
-hop no.

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11
Q

what does sequence of data packet allow

A

correct reassembly of data packets

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12
Q

what is in payload

A

-data

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13
Q

what is in trailer

A

-method of identifying end of packet
-some form of error checking

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14
Q

max hop count

A

30

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15
Q

define packet switching

A

-forwarding packets form 1 router to another leading towards its destination

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16
Q

difference btw packet & circuit switching

A

packet:
-no fixed route
-diff speed for each packets
-have to reorder at arrival
-less expensive
-packets travel independently
-don’t reserve bandwidth
circuit:
-dedicated pathway
-uniform delay of packets
-packets are in order
-more expensive
-packets travel in same path
-reserve entire bandwidth

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17
Q

advantages for packet switching

A

-no single com. needed
-packet can be resent by rerouting if it fails = high speed transmission
-relatively easy to expand packet usage
-high data transmission rate possible

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18
Q

disadvantages of packet switching

A

-can be lost & need to resend
-more prone to errors for real time streaming
-delay at destination = have to reassemble

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19
Q

explain how packet switching works

A

-data is split into multiple packets
-each packet follows its own path to the destination
-routers determine the path
-rout is selected depending on no. packets in each router
-shortest path is selected

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20
Q

define bouncing packets

A

-packets move back & forth btw routers & never reach destionation

21
Q

what happens after max hops

A

-packet is destroyed & resent

22
Q

explain problems caused by bouncing packets

A

network could stop because lost packets mount up and ‘clog’ the system

23
Q

how is an email sent

A

-email is broken into packets
-IP source, IP destination, sequence no., packet size, total no. packets added to header
-router checks hop no. and IP destinations of packet & determines shortest path
-packets takes diff routes and arrive at diff times
-packets are checked for errors & reassembled according to sequence no.

24
Q

which form of switching is more reliable

A

circuit, has dedicated channel

25
Q

how are the delay btw packets in circuit switching

A

uniform delay

26
Q

how does circuit switching work

A

Connection establishment:
-all packets know entire path address
-data processed at source system only
-have fixed channel
Data transfer:
-delay btw packets is uniform
-resource reservation = fixed path = more wastage
Connection released

27
Q

advantage of circuit switching

A

-dedicated pathway
-packet arrive in order
-no delay in transmission
-Ideal for certain types of traffic

28
Q

disadvantage of circuit switching

A

-inefficient resource utilisation
-Delay when establishing channel
-higher cost = fixed channel

29
Q

eg of packet switching

A

-internet browsing
-file download & upload
-emails & instant messages

30
Q

eg of circuit switching

A

-traditional cell phone call
-Cellular voice call (Non-VoLTE)
-dedicated fax lines

31
Q

types of transmission mode

A

-simplex
-half-duplex
-full-duplex

32
Q

types of data transmission

A

-serial
-parallel

33
Q

define simplex transmission mode

A

-data is sent from 1 direction
eg. comp - printer, radio station - person, TV - person

34
Q

define half-duplex transmission mode

A

-data is sent from 2 direction but not at same times
eg. walkie - talkie

35
Q

define full-duplex transmission mode

A

-data is sent from 2 directions at same time
eg. messaging at same time, live call

36
Q

define serial transmission

A

-data sent 1 bit at a time over a single channel
eg. comp - printer via USB

37
Q

define parallel transmission

A

-data sent in multiple bits over multiple channels
eg. internal circuit in comp

38
Q

diff btw serial & parallel transmissions

A

serial:
-good over long distance
-data sent in correct order
-slower over short distance
parallel:
-good over short distance
-data not sent in correct order
-faster over short distance

39
Q

what happens to data over long distance using parallel transmission

A

-parallel is better over short distance
-data is skewed
-longer the wire, more skewed

40
Q

define USB

A

-Universal Serial Bus is a form of serial data transmission

41
Q

what happens when device is plugged in comp

A

-comp. auto detect device from change in voltage in on data signal wire in USB cable
-device is recognised & device driver software is loaded for com.
-comp will look for device driver that match device. If not available, user is asked to download the software

42
Q

advantages of USB

A

-devices plugged are auto detected & device drive is auto loaded up
-connection only 1 way = prevent incorrect connection
-is industry standard = considerable support available
-support diff transmission rate
-no need external power source
-error-free transmission = USB protocol notify to re-transmit if error detected
-backwards compatible
-easy to use
-high-speed data transmission

43
Q

disadvantages of USB

A

-standard UBS support only 5m
-some early UBs may not be supported by latest comp.s
-slower data transfer rate than Ethernet

44
Q

how much power does UBS cable supply

A

+5 V

45
Q

USB types

A

-A
-B
-C
-mini A
-mini B
-micro A
-micro B
-micro B super speed

46
Q

diff wires in USB

A

-black
-green
-white
-red

47
Q

USB type C

A

-24 pin symmetrical connector
-smaller than older UBS connectors
-20V power connectivity = 10Gbps = support 4K video
-backwards compatible

48
Q

how can packet switching cause errors in vid & sound

A

-pic & sound not in sync = packets arrive at diff times
-pauses in vid = time delay in assembling packets
-degraded vid & sound = competing traffic on con. link
-possible ‘drop out’ = packet take diff route & may get lost

49
Q

note:
-when drawing serial half/ full duplex, draw 2 line - dotted & undotted
-be careful of which devices to use, eg need a web server

A

Comp sci (12 decks)

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