a - cs > chapter 2 - networks > Flashcards

chapter 2 - networks Flashcards

(59 cards)

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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

Study These Flashcards
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
hybrid topology
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
network topologies
- point to point - bus - mesh - star - hybrid
27
public cloud
-client and company are separate entities eg google docs, one drive not owned by companies using it
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private cloud
- Storage provided by a dedicated environment behind a company firewall - client and storage provider are integrated / same and operate as a single entity
29
cloud storage +
+ 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
cloud storage -
-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
modes to send data ( ways) - transmission
- Simplex - one way - half duplex - data flows either way but not simultaneously - full duplex - simultaneous data flow both ways
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how to send data (who to) - message type
- Broadcast - one to all communication - multicast - one source to many destinations - Unicast - one to one communication
33
twisted pair cable
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
coaxial cable
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
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fibre optic cable
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
single vs multi mode
**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
radio waves
used by bluetooth and WiFi uses spread spectrum freq hopping - picks one channel and if that channel is being used picks another
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bluetooth
- 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
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WiFi
- also uses spread spectrum freq hopping - has faster data transfer - better range - better security - accesses internet via WAP
40
microwaves
For most applications microwaves are best as they have a better bandwidth than radiowaves
41
infrared
- 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
satellite
- 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
wired +/-
+ 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
wireless +/-
+ easier to expand + increase mobility - increased interference - less data security (easy to intercept data) - slower transmission - signals can be stopped by thick walls
44
cabling on LANs
nowadays mostly twisted pair cables and fibre optic becoming more common
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bridge
- 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
repeater
- 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
hubs with repeaters negatives
- 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
hub
- 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
switch
- 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
router
- 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
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NIC
- component used to identify the end system - has a unique network address - contains MAC address
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WAP
- connecting device in a WiFi LAN - provided the system has a WNIC installed
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server
- 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
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gateway
- acts as an entrance to a network – converts packets to different protocols
55
ethernet
- 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
how does ethernet reduce collisions
- 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
PSTN
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
ethernet conflicts
- 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
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