Networks Flashcards

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1
Q

Define Serial data transmission

A

when bits are sent one after another along the same data line

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2
Q

Define Parallel data transmission

A

several bits are sent simultaneously along separate lines or channels

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3
Q

what is skew and how is it caused

A

it is when data arrives unsynchronised , as each individual wire has slightly different properties bits travel at slightly different speeds along each of the wires

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4
Q

what is crosstalk and its problems

A

it refers to electromagnetic interference between two adjacent channels or parallel wires. It gets more pronounced as the frequency increases.

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5
Q

What type of transmission is preferred for long distances

A

serial transmission is reliable over very long distances at very high data transfer rates (frequencies)

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6
Q

At what distance can parallel transmission be used up to?

A

around 2m due to crosstalk

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7
Q

what is an example of a serial connector and its benefit

A

USB connecters are much smaller and cheaper than parallel connectors

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8
Q

define synchronous data transmission

A

all data transfers are timed to coincide with an internal clock pulse.

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9
Q

How is Data sent using synchronous transmission

A
  • The data is sent as one long stream with no gaps in transmission
  • The receiver counts the bits and reconstructs bytes
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10
Q

Define asynchronous data transmission

A

each byte is sent seperately the moment it is available instead of waiting for a clock signal

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11
Q

How are bytes sent in asynchronous transmission

A

each byte is preceded by a start bit and ends with a stop bit or stop period - a short time gap between each set of bits

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12
Q

what is a parity bit

A

it is added as the 8th bit as a form of error detection, this bit is set to a 1 or 0 to make the total number of 1’s or 0’s in each byte odd or even depending on the machine

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13
Q

disadvantages and advantages to asynchronous transmission

A
  • relatively slow owing to the increased number of bits sent

* it is a cheap and effective form of serial transmission suited to low speed connections like a KnM

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14
Q

Define Latency

A

It is the time delay between the moment the first byte or packet of a communication starts and when it is received at its destination

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15
Q

Define protocol

A

The set of rules relating to communication between devices, all communications between devices require the devices agree on a format of the data.

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16
Q

what things do the protocol need to define

A
  • standards of physical connections
  • rate of transmission
  • data format
  • type of transmission a/synchronous
  • error checking procedures
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17
Q

Define bit rate

A

the number of bits transmitted in one second over a wired or wireless data link

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18
Q

Define Baud rate

A

the rate at which the signal in a communications channel changes state

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19
Q

What is a baseband, and how are bits sent along it.

A

it carries one signal at a time, a bit is represented by a high or low voltage in the cable

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20
Q

Define Broadband

A

it carries multiple signals on a fixed carrier wave. bits are sent as variations on the wave

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21
Q

what is the formula for bit rate

A

bit rate = baud rate x number of bits per signal

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22
Q

Define Bandwidth

A

it is a measure of the maximum capacity of a communications channel

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23
Q

Define Local Area Network

A

two or more computers connected together within a small geographical area

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24
Q

what is a network topology

A

it is the arrangement of the various computing devices which make up a computer network

25
Q

what is a bus topology

A

an arrangement where nodes are connected in a daisy chain by a single central communications Channel

26
Q

what is a star topology

A

an arrangement where a central node or hub provides a common connection point for all other nodes

27
Q

how does a bus network operate

A
  • All nodes are connected to a backbone cable
  • Each end of the backbone is connected to a terminator which stops signals bouncing back
  • Each node is passive
  • Data is sent in one direction
  • Only one computer can transmit at one time
28
Q

what protocol is used to enable nodes to transmit on the same cable

A

carrier sense multiple access (CSMA/CD)

29
Q

What are advantages to a Bus topology

A
  • Cheap
  • devices can easily be added
  • Good for small networks
30
Q

What are disadvantages to a Bus topology

A
  • Main cable is a point of failure
  • Limited cable length
  • Performance degrades with heavy use due to data collisions
  • Poor security
31
Q

What does CSMA do

A
  • It detects two nodes attempting to transmit simultaneously
  • Both nodes cease transmission and wait a random time (backing off mechanism)
32
Q

Difference between a hub and switch

A

a switch sends communications to the specific computer it is intended for and a hub broadcasts the message to every computer on the LAN

33
Q

How does a switch identify and locate where to send data

A

it holds the MAC addresses for each device connected to it and uses these to direct packets of data to the correct device

34
Q

What are advantages to a star network

A
  • Easy to isolate problems
  • Good performance
  • More secure if a switch is used as data is sent only to recipient
35
Q

what are disadvantages to a star network

A
  • Can be expensive to set up because of the length of the cable
  • Central device is point of failure
36
Q

what is a physical topology of a network

A

it defines how the devices are physically connected to one another

37
Q

what is a logical topology

A

it defines how the devices communicate across the physical topologies

38
Q

what is a server

A

it is a powerful computer which provides services or resources required by any of the clients

39
Q

what is a client

A

it is a computer which requests the services or resources provided by the server

40
Q

what is the role of the client

A
  • the client sends requests to the server
  • waits for a reply
  • receives the reply
41
Q

what is the role of the server

A
  • The server waits for requests from the clients

* it may need to pass the request to another server in which case It becomes the client

42
Q

what are features of a client-server network

A
  • central server is used to manage security
  • some files are held on the central server
  • some processing tasks are performed by the server
  • can require specialist IT staff to administer the network
43
Q

give examples of types of servers

A
  • web server
  • print server
  • Mail server
  • File server
  • Database server
44
Q

what is peer to peer networking?

A

when each node on a server is able to send requests and process them.

45
Q

what are features of a peer to peer network?

A
  • suitable for small companies
  • cheaper as it doesnt require hardware
  • all computers can easily share/see files on all other computers
  • if a computer is switched off, data cannot be retrieved
46
Q

what can peer to peer on a WAN be used for?

A
  • the P2P configuration can be used for file sharing websites
  • P2P networks are used for illegal distribution of material.
47
Q

what is cloud computing?

A

internet computing using remote servers run by organisations

48
Q

Advantages of cloud computing?

A
  • some software doesnt have to be downloaded to the users computer.
  • software and data is accessible from any computer anywhere in the world
  • the data is automatically backed up so there is no danger losing it
49
Q

define wi-fi

A

it is a wireless networking technology providing high-speed internet and network connections

50
Q

How do devices connect to the internet

A

via a WAP

51
Q

what is needed to connect to a wireless network

A
  • ISP
  • Modem and wireless router
  • Device with NIC
52
Q

what makes up wireless networking?

A
  • wireless NIC
  • station consists of a computer and a NIC
  • stations share a radio frequency channel
  • WAP requires a connection to a router, and the router requires a connection to a modem
53
Q

What is an SSID

A

service set identifier ; identifies each network by a locally unique name

54
Q

what are features of an SSID?

A
  • can be set manually or automatically
  • can be hidden to make it hard to detect
  • must be used by all devices on that network
55
Q

what are disadvantages to wireless networks

A
  • wireless networks are less secure; prone to man in the middle attacks, packet interception, cookie stealing
  • unauthorised users can be hard to spot
56
Q

What are security measures used by wireless networks

A
  • WPA
  • WPA2
  • MAC address whitelist
57
Q

what is the CSMA (Carrier Sense Multiple Access) algorithm ?

A
58
Q

what are the consequences of using CSMA

A

collisions are avoided by each station transmitting only when the channel is idle

59
Q

what happens when you use CSMA/CA with RTS/CTS

A