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a - cs > chapter 2 - networks > Flashcards

chapter 2 - networks Flashcards

1
Q

benefits of networking

A
  • share resources eg printers which reduces cost
  • share files/ data
  • data can be backed up centrally
  • managers can manage the network eg apply access rights
  • can communicate
  • licences to run software on a single network is often cheaper than on many computers
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2
Q

drawbacks of networking

A
  • expensive hardware
  • expensive / hard to manage
  • if on device breaks eg file server it affects the whole network
  • malware can affect the whole network
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3
Q

MAC address

A
  • 48bit hexadecimal separated into 6 bytes
  • physical hardware address and is unique
  • assigned to NIC by manufacturer
  • identifies devices
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4
Q

what is an ISP

A

provides access to the internet eg EE vodaphone

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5
Q

internet browser

A

accesses the internet via an app eg bing

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6
Q

LAN vs WAN

A
  • LAN is over a smaller physical area whereas WAN is over a many different locations
  • individual vs shared ownership
  • faster vs slower
  • twisted pair cable/wifi vs fibre optic
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7
Q

LAN +

A

+ expense of installing software on individual PCs could be reduced
+ file server can be connected to allow sharing
+ can share resources eg printers reducing cost and allowing higher quality resources to be brought
+ office can become paper less

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8
Q

WAN +

A

+can run a ‘job’ on a remote comp that required the application software
+ data archive stored on a remote computer that could be accessed
+ a message could be transmitted electronically to a user on a remote comp

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9
Q

IP address

A
  • assigned by the router
  • identifies the device on the network
  • can change if location changes
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10
Q

internet vs www

A

internet is the hardware that the www runs on
www is the software that runs on the internet
eg email - uses www to open web browser and email account but internet at acc send to different computers

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11
Q

client server model

A

where a client runs an application provided by a server on a network -
- uses separate servers and client computers
- users can access files which are stored on servers
- server supplies resources and client consumes them
- used to share data

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12
Q

thin client

A

choses an application to run on a server and only provides input and receives output from the server - doesn’t process on the client

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13
Q

thick client

A

carries out some of the processing itself

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14
Q

thin client +/-

A

+cheaper to expand
+all devices linked to server
+ server offers protection against hacking and malware
-reliant on the server - if it breaks
-higher start up costs – more complex – powerful servers needed

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15
Q

thick client +/-

A

+ more robust
+ clients have more control
-data integrity - since many clients access same data
-less secure
- each client needs to update data individually

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16
Q

peer to peer model

A
  • each node is connected to the other nodes = status
  • each responsible for own security
  • users access data from each other - act as provider and consumer
    Used for - smaller less secure networks where workstation based applications are needed - for connectivity
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17
Q

server definition

A
  • provide functions
    – have dedicated roles and run software to perform dedicated tasks eg file servers, windows server, web servers
    – client requests service server provides
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18
Q

frame/packet

A

unit of transfer containing the data, address and control info

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19
Q

peer to peer +/ -

A

+ avoids congestion on the network when many clients are downloading files at the same time
+ parts of a file can be downloaded separately
+ the parts are available from more than one host
- less secure
- no central backup
- all comps have to be on to share files - might not always be available

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20
Q

client- server +

A

+ allows an organisation to control downloading and use of some files
+ files can be better protected from malware attacks because the files are stored on one server which can be scanned using anti virus software

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21
Q

bus topology

A

central main cable
+ cheap to install
+ even if one node fails test function
- if cable fails no data can be transmitted
- increased traffic down central backbone
- poor security as all computers can see transmissions along shared cable

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22
Q

star topology

A

central switch
+ if cable fails other computers aren’t affected
+ easy to add new computers
+ less traffic as its isolated between computers
+ no data collisions
- costly to install - extra hardware
- if central node fails so does whole network

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23
Q

point to point topology

A
  • one comp to one comp
  • Transmission can be simplex or duplex
  • Message is unicast
    + simple
    neg- only 2 comps
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24
Q

mesh topology

A

Each comp has a point to point connection to another comp - direct links - can act as relays passing packets towards the destination
- Transmission is duplex
- Messages are unicast, multicast or broadcast
+ easy to see where faults are
+ broken links don’t affect other nodes
- lots of cabling
- complex set up

25
Q

hybrid topology

A

collection of connected LANs where they have diff topologies or supporting technologies
+ large volumes of traffic
+ east to see where faults are
+ good for large networks

26
Q

network topologies

A
  • point to point
  • bus
  • mesh
  • star
  • hybrid
27
Q

public cloud

A

-client and company are separate entities eg google docs, one drive
not owned by companies using it

28
Q

private cloud

A
  • Storage provided by a dedicated environment behind a company firewall
  • client and storage provider are integrated / same and operate as a single entity
29
Q

cloud storage +

A

+ files can be accessed at any time (with internet access) by any device
+ no need to carry an external storage device with you (heavy) - less stuff on hard drive
+ remote back up - adds security
+ data can be recovered
+almost unlimited storage capacity
+ cheap - some are free

30
Q

cloud storage -

A

-if no internet/slow - cant download data/files
-costs can be high if large storage capacity required - can build up if have a subscription model (long term costs)
-expensive to pay for the necessary high download/ upload limits (high bandwidth) from the ISP
-trust in third party company to not lose data/ have a failure

31
Q

modes to send data ( ways) - transmission

A
  • Simplex - one way
  • half duplex - data flows either way but not simultaneously
  • full duplex - simultaneous data flow both ways
32
Q

how to send data (who to) - message type

A
  • Broadcast - one to all communication
  • multicast - one source to many destinations
  • Unicast - one to one communication
33
Q

twisted pair cable

A

eg connect telephone handsets to telephone lines
- cheapest
- lowest bandwidth
- affected by attenuation
- most affected by interference - uses lots of, thinner wires with less insulation
- more need for repeaters
can be unshielded or shielded (commercially used to cancel out interference)

34
Q

coaxial cable

A

eg used by cable television companies in MANs
- higher cost
- higher bandwidth - as its thicker
- most affected by attenuation
- less affected by interference
- more repeaters needed

35
Q

fibre optic cable

A

uses pulses of light not electricity
can be single or multi mode
doesnt bend due to mirrors being used
eg long distance cabling
- highest cost
- highest bandwidth
- least affected by attenuation
- least affected by interference
- less repeaters needed

36
Q

single vs multi mode

A

single
- uses a single mode light source
- smaller central core so less reflection
- can travel faster/further
eg CATV or telecommunications
multi
- works for multi mode light source
- construction causes higher light reflections in core- work best in shorter distances
eg LAN

37
Q

radio waves

A

used by bluetooth and WiFi
uses spread spectrum freq hopping - picks one channel and if that channel is being used picks another

38
Q

bluetooth

A
  • sends radio waves at 79 frequencies (channels)
  • 2.45GHz freq
  • devices automatically detect and connect to each other (each device uses a diff channel so they don’t interfere)
    used for multiple close devices - slow speed - low bandwidth
39
Q

WiFi

A
  • also uses spread spectrum freq hopping
  • has faster data transfer
  • better range
  • better security
  • accesses internet via WAP
40
Q

microwaves

A

For most applications microwaves are best as they have a better bandwidth than radiowaves

41
Q

infrared

A
  • highest bandwidth and best at focussing directionally
  • but most attenuation, needs repeaters most, worst penetration
  • mainly used for indoors as it cannot escape and cause interference elsewhere (benefit)
42
Q

satellite

A
  • Transmitted between antennae
  • uses microwaves and radio waves
    + Enable long distance communication
    + less interference
    + compensates for the curvature of the earth so can communicate globally
  • Can be transmission delays due to greater distances which cause technical problems
43
Q

wired +/-

A

+ more reliable/ stable - less interference
+ data transfer is faster - no dead spots
+ overall cheaper in spite of need for hardware
- devices aren’t mobile
- trip hazard / fire risk from cables

43
Q

wireless +/-

A

+ easier to expand
+ increase mobility
- increased interference
- less data security (easy to intercept data)
- slower transmission
- signals can be stopped by thick walls

44
Q

cabling on LANs

A

nowadays mostly twisted pair cables and fibre optic becoming more common

45
Q

bridge

A
  • connects two segments of a LAN ( that use the same protocols) so they can function as one LAN
  • stores the network address for the end-systems in the two segments it connects
46
Q

repeater

A
  • a device which connects two cables and provides a full strength signal (over long distances signals become attenuated ao this reduces that by generating a new full strength sigbal) to the second cable
  • can be used to extend a bus by connecting two bus cables - and boosts all signals to prevent dead spots in the WiFi zone
47
Q

hubs with repeaters negatives

A
  • collisions may occur and are not resolved - one way to deal with this is to use jamming signals however this reduces performance
  • they are unable to manage delivery paths and security
48
Q

hub

A
  • can have a number of devices connected to them so are used to connect devices to form a LAN
  • takes a data packet recieved at a port and sends the data to every computer in the network
  • not secure and wasteful use of bandwidth
49
Q

switch

A
  • a connecting device that can send a unicast message
  • central device on a star network
  • can direct communication to a specific-end system
    + More efficient than hubs as they check the data packets received and works out its address and sends data only to the appropriate computer - more secure
50
Q

router

A
  • routes data between different networks to the appropriate switch eg joins LANs to WANs
  • can take data and format it into different protocols to be used on different networks
51
Q

NIC

A
  • component used to identify the end system
  • has a unique network address
  • contains MAC address
52
Q

WAP

A
  • connecting device in a WiFi LAN - provided the system has a WNIC installed
53
Q

server

A
  • a system providing a service of end-systems
  • provides functions – has dedicated roles and runs software to perform dedicated tasks eg file servers, windows server, web servers
    – client requests service server provides
54
Q

gateway

A
  • acts as an entrance to a network – converts packets to different protocols
55
Q

ethernet

A
  • The dominant LAN protocol
  • Originally used on a bus configuration
  • Used CSMA/CD to minimise the effect of collisions
  • Modern version is switched
    Made up of:
  • a node eg any device on the LAN
  • medium - a path used by the LAN devices eg Ethernet cable
  • Frame- data is transmitted in frames - made up of source address and destination address (MAC + IP)
56
Q

how does ethernet reduce collisions

A
  • Uses broadcast transmissionn so data can be sent at the same time causing collisions
  • Uses **CSMA/CD **
  • when a collision is detected the node stops transmitting a frame - transmits a ‘jam’ signal - then waits for a random time interval before trying to resend the frame
57
Q

PSTN

A

public switched telephone network
- cables used to connect devices/LANs between towns/cities
- Changed from copper to fibre optic (faster broadband)
- Always open even so can always be used
- Remains active during power cut - have separate power source
- Use circuit switching - connection is maintained for the duration of the call

58
Q

ethernet conflicts

A
  • it is possible for IP addresses to conflict
  • may occur is devices on the same network have been given the same IP address - most likely on LANS with dynamic IP and static
  • can be resolved by restarting the router - so IP will be reassigned

a - cs (20 decks)

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