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A2 Digital Tech > Networks > Flashcards

Networks Flashcards

1
Q

What is a computer network

A

Two or more computers connected together so that they can communicate

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2
Q

What is a LAN

A

Local area network

Covers a small geographical area such as a single site building e.g school

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3
Q

What is a MAN

A

Metropolitan Area Network
Covers a highly populated area such as a town or city
Technology such as fiber optic and wireless

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4
Q

What is a WAN

A

Wide area network
Covers a large geographical area such as a country or globally e.g bank c2k
Technology such as telecoms ie underwater fiber optics mobile networks satellites etc

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5
Q

What is a Network Interface controller (nic)

A

Every node on a network needs a NIC

Provides a our for cable to plug in or wireless protocol (WiFi)

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6
Q

What is a media converter

A

Transforms the signal from one media type to another e.g Turing a hdmi signal into a usb or Ethernet to fiber optic

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7
Q

What is a Wireless Acces point (WAP)

A

Connection point for multiple devices on a network

Turns WiFi protocol domhnall to Ethernet and vice versa

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8
Q

What is a switched huh (switch)

A 
Central Connection point
Bring multiple nodes together
Manages data traffic on network 
Passed data packets to the distinction node
Using Mac addresses 
Address table
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9
Q

What is a repeater

A

Voltage drops over long distance
Resistance in copper cables
Eventually it is not understood by system
Repeated reconstructs the original signal and forwards it on
May need multiple repeaters over very long distances

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10
Q

What is a file server

A 
Allows users to log in 
Security such as access rights
Store all users files
Manage and share network resources
Print server
Proxy server
Email server
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11
Q

What is a MAC address

A

12 hex digits
Every network or communication interface card has a unique MAC address assigned by manufacturer when created
Permanent cannot change
Used for LAN addressing

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12
Q

What is an IP Address

A

4 denary numbers know as octets
IP addresses are assigned by DHCP server when device connects
Used for internet addressing
Every computer on internet has a unique IP address

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13
Q

How is an IP address assigned??

A 
DYNAMIC 
An IP address will be assigned to a device each time it connects to a network 
From a pool of available addresses
Within network range 
Can be different each time

STATIC
An IP address is assigned the first time it connects
Same address is reserved for this device
Every time it’s connected
But the static address can be changed

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14
Q

Compare Sever Based Network and a Peer to Peer Network

A

Server Based Network
One controlling computer on the network
.. Accepts request for services e.g. files, printing etc
.. Mist provide those services (allowed by security)
Centralized control
Lots of maintenance takes from one location
Backups
Security
Installing software

Peer to Peer Network
All computers are equal
Computers are both consumers of and provides of services e’g sharing files
Computers do not have to provide services e.cpu is busy
Each node make some resources available eg cpu files
Need to make changes to every individual computer e.g. security settings, installing new software updates backups etc.

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15
Q

What is a bus topology

A

It is when 1 communication line is shared
…Data is transmitted in all directions on bus
… Data is seen by lo nodes
Which is ignored by all except the addressed node
Uses CSMR

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16
Q

What is a ring topology

A

Each node has links to 2 other nodes in loop
Data moves in one direction around the ring
..using token passing
Possible that I have 2/dual ring network
Passes from node to node until it reaches final destination

17
Q

What is a star topology

A

Every Computer has a dedicated communication link back to server
…All data is sent to central point and then forwarded to connect node

18
Q

Compare the three topology regarding Adding new nodes

A

Bus: power down network… cut cabling and bus, to insert a t connector and plug in a node

Ring: remove 1 cable link it to a new node and add cable from new node to next node

Star: plug node into port if available
If not add a hub and plug into that

19
Q

Compare the three topology regarding cost

A

Bus: Cheaper because it is just one cable

Ring: cheap (not as cheep then bus) need more ports cables and network cards

Star: very expensive each node has cable going all way back to server

20
Q

Compare the three topology regarding speed

A

Bus: slowest
1 data line, 1 packets can be transmitted at a time
A lot of problems as network grows
Many more controllers and bottle necks

Ring: Deal with more nodes than a bus with less disruption to speeds
…Especially with dual ring
…No collisions
…up to a certain point

Star: Fastest no collision as they all have dedicated lines
Every node could be sending simultaneously

21
Q

Compare the three topology regarding security

A

Bus: least secure
All nodes hear all message

Ring: not that secure
Messages are passed through various nodes

Star: most secure as messages passed only to the addresses node

22
Q

Compare the three topology regarding increasing the number of nodes

A

Bus: Doesn’t scale well
Too many nodes = too much traffic
Won’t be able to come

Ring: Scale better than bus
Multiple communication simultaneously
Reaches a point where too much traffic on network
Improved if dual ring

Star: Easy to scale
Every computer has own communication line
Extended star (segment network)

23
Q

Compare the three topology regarding robustness

A

Bus: single cable failure and no network - not very robust

Ring: one or two failures bring down network

Star: very robust, cable failure only affects node connected to it
,,, central hub is it weak point

24
Q

What is Bandwidth

A

Bandwidth is a value that refers to the maximum amount of data that is transferrable across a given medium in a given period of time

25
Q

What is Broadband

A

It is a higher transmission rate (bandwidth)

Higher than dial-up (54 kbps) or ISDN (128Kbps)

26
Q

What is the Ethernet

A

Set of protocols for hardware and communications
Hardware e.g. coaxial cable
Twisted Pair

27
Q

What is a Twisted Pair

A

8 Cables in 4 pairs
That are colour coded
They are twisted in pairs all together which provides with some shielding properties
It can have additional outer shielding
for noisy environments of electromagnetic radiation
e.g. Cat 5, Cat 6, Cat 6E
More twisting = More copper - Added Shielding = Greater Bandwidth - Higher Price

28
Q

What is Fibre Optics

A

Light travelling along glass fibre (cable)
Total Internal Reflection
…No loss of light (signal)
…Huge distances without the need for repeaters
…The light beam reflects off internal surface/edge of glass fibres
Multi-Mode Fibre
More than one light sensor simultaneously
on the same fibre optic strand
at different light frequencies with multiplying speeds
I.E. Even Higher Speed

29
Q

What is WiFi

A 
Wireless Fidelity
Used Radio signals to encode data
Different protocols within standards (802.22)#
e.g. b,n, ac etc..
Rates from 54 Mbps to 600 Mbps
24 GHz range (also 5 GHz Range)
11 Wifi Channels in range
30
Q

Compare the three technologies (WiFi, Ethernet and Fibre Optic) in terms of security

A

WiFi

  • Transmitted Over Air
  • Transmitted everywhere in range (Problem
  • So it must be encrypted

Ethernet
-Data on cables
-Need Physical Access (better than wifi)
- Could be located inside walls or underground
-If physical access
… Tap by using Electromagnetic Radiation
… or by using a physical connector with copper

Fibre Optic
-Data on cables
- Need Physical Access
If accessed
-No electromagnetic radiation, light is totally internal (better than ethernet)
- Cannot cut into a Fibre Optic cable without destroying it

31
Q

Compare the three technologies (WiFi, Ethernet and Fibre Optic) in terms of Bandwidth

A

Wifi
-Slowest
-Shared Channels (1 per aerial)
-If there are 5 channels, some channels must be shared
-Lead to collisions (requires data to be resent)
Radio is slower than electrical signals

Ethernet

  • Each computer has own cable (Better than Wifi)
  • Ethernet has a higher bandwidth than wifi

Fibre Optic

  • Speed of light
  • No loss of signal
  • Large distances, no need for booster/repeater
  • V.High bandwidth
32
Q

How does Error Checking work

A

-First Node transmits the message to the receiving mode
-The receiving node transmits the same message back
- The first node compares what is sent to what it received back
… If the message matched = There was no error
… If the message did not match = Error Detection

33
Q

How does Parity Checking work

A

There are two forms of Parity check, Odd or Even

  • It is used to check a chunk of data e.g.byte
  • The least significant bit is used as a parity check digit
  • The Odd number = Odd number of 1s and 0s (10010100) (3 x 1s) (5x0s)
  • The Even number = Even Number of 1s and 0s (10010101) (4 x 0s) (4x1s)
  • transmitting device sends data, it counts the number of set bits in each group of seven bits.
  • if the number of set bits is even, it sets the parity bit to 0
  • if the number of set bits is odd, it sets the parity bit to 1. In this way, every byte has an even number of set bits.
  • On the receiving side, the device checks each byte to make sure that it has an even or odd number of set bits. If it finds an odd or even number (opposite one) of set bits, the receiver knows there was an error during transmission
34
Q

What is the problem with parity check

A

It detects bits that have been flipped 0-1 1-0

It cannot detect an even number of flips

35
Q

What is check sum and how does it work

A

-Same as any other check digits

Except the calculated value may be longer than 1 digit

36
Q

What is error correction

A

If an error is detected by echo checking, parity checking or checksum, we still need the correct data to be transmitted
The simplest form of connection is RESENDING
Going through the same process again

37
Q

What is a checksum and how does it work

A

Checksums involve counting the number of 1 BIT’s in a packet and sending this as a mathematical total at the end of the packet.
The process involves the data packet ‘checking itself’ at the destination looking for errors; if errors are found the data will be transmitted again

38
Q

What is a Cyclic Redundancy Checks

A

Cyclic Redundancy Check (CRC) is an error detection mechanism in which a special number is appended to a block of data in order to detect any changes introduced during storage (or transmission).

  • It detects and corrects errors automatically
  • The checksum is added to the chunks of data before transmission
  • Forward Error Checking uses longitudinal and latitudinal parity checks
  • The CRC is recalculated on retrieval (or reception) and compared to the value originally transmitted

A2 Digital Tech (6 decks)

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