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GCSE Computer Science > Computer networks, connections and protocols > Flashcards

Computer networks, connections and protocols Flashcards

1
Q

avantages netowrking

A

users can share files
users can share peripherals and connections to other netowrks e.g internet
users can access files from any comp on network
servers can control secuiry software updates and backup of data
communication w/ other ppl

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2
Q

two types of netowrk

A

LAN -Local area network
WAN - wide area network

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3
Q

LAN

A

covers small geogrpahic area
all hardware for lan owned by organisation useing it
LANs are wired w/ utp cable, fibre optic or wireless using wifi

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4
Q

WAN

A

large geographic area connecting lans together
infrastructure between lans leased from telecomunication companoes who own and manage it
wans connected by telephone lines, fire optic cables or satellite links

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5
Q

what are computers in lan connected to

A

a switch

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6
Q

what are computers in wan connected to

A

router

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7
Q

job of the router

A

personal home device for connecting to internet - multi function all in one device:
acts as router, switch and wireless access point

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8
Q

disavantage netowrking

A

increased secuiy risk to data
malware and viruses spead very easily between comps
if server fials comps connected to it may not work
computer may run more slowly if lots of data travelling over netowrk

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9
Q

how does bandwidth affect performance of netowrk

A

bandwidth is amount of data that can be sent and received successfuly in given time
not a measure of how fats data travels, but how much data can be sent on transmission media
mesaured in bits per sec (bit rate)

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10
Q

factors affecting erofrmace of netork

A

bandwidth
num of users
transmission media
latency
error rate

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11
Q

how does num of users affect netork performances

A

too mnay users slow down netowrk if insuffiencient bandwidth for data

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12
Q

how does transmission media affect performance of netowrk

A

wired connections have highhr bandwidth that wireless
fibre optic cables have higher bandwidth than copper cables

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13
Q

how does error rate affect netowrk performance

A

less relible connections increase num of erors occuring when data transfered
means data has to be resent until ariving correctly
signal quality of wirelss connections dpeendant on range of devics from wirelss access point and other envitonmental factors
signal quaity of copper cables determinded by grade of material used which reduces interference
length of cable also a factor

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14
Q

how does latency affect netowrk per4mance

A

latency is delay from transmitting data to receiving it
caused by bottlenecks in infrastructure of netowrk
eg by not using switches to apporpriately segment traffic on netowkr
hardware such as switches and transmission media may not operate on same spd

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15
Q

whats a server

A

special comp on netowrk not used as workstation
dedicated to serving files and managaing other services
both LAN and WAN can use servers

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16
Q

what is a netowrk using a server and what is a network not using a server

A

using server:
client server model

not using server:
peer to peer model

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17
Q

job of server

A

control access and security to one shared file store
manages access to internet
manages printing jobs
provides email services
runs a backup of data
makes reuqests to server for data and connections

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18
Q

avantages client server model

A

easier to manage security files
easier to take backups of all share ddata
easier to install software pdates to all computers

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19
Q

disavantages client server model

A

expensive to setup and maintain
requires it specilaists to maintain
server is single point of failure
users will lose access if server fails

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20
Q

what is a peer

A

comp on a network, is equal to other peers

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21
Q

how does peer-2-peer model work

A

peers serve own files to each other
each peer resposnsible for own security and backup
peers have own printers
can send print jobs to another peer to process but other peer must be switched on to communicate ith connected printer

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22
Q

avantge peer2pper model

A

very easy 2 maintain
specialist staff not reuqired
no dependency on single comp
cheaper to set up
no expensive hardware required

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23
Q

disavantage peer2p model

A

network less secure
users need to manage own backups
can be difficult to maintain well ordered file store

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24
Q

what does every comp need to connect to network

A

NIC - Netowrk interface card
every device on a network has a NIC

they are integrated into comp
use a protocol (a set of rules) to determine how connection should work
allw a device to conect to either wired or wireless netowrk

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25
Q

WAP

A

wireless access point
allowes wireless enabled devies to connect 2 network without cables
more convenient
less bandwidth than wired connection
secuirty more a concern with wirless connections
connection sometimes not as strong or relaiable as wired connections

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26
Q

a switch (hardware to connect to lan, in detail)

A

sends data between comps on a lan
segment network by forwardibg traffic to correct location
learn which devices are connected and understand how to forward traffic in intelligent way
uses NIC address on device to route traffic

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27
Q

a router (detailed)

A

sends data between networks
creates a wan from a number of lans
cannot connect to a wan withot router
uses IP address (internet protocol) to route traffic

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28
Q

transmission media - copper cables (utp)

A

wired connections assure max bandwidth security and reliability
with twisted pair cables wires are twisted around each other to reduce interference
there are normally a set of wires for transmission and 4 receiving
gradeof copper and insulating material aggects quality of overall cable and therefore the bandwidth

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29
Q

transmission media - fibre optic cables

A

uses light to transmit data
cover much longer distances and greater bandwidth than copper
backbone of internet uses fibre optic cables

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30
Q

def protocl

A

a set of rules that allow two devices to communicate

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31
Q

why are copper cables used

A

theyre cheap and fleible - easy to install

32
Q

what is the internet

A

most widely known WAN
collection of interconnected networks
not the same as world wide web which is a service on internet

33
Q

the internet detail

A

home network connected via wirelss router
home router connected to internet service provider
isp is connected to domain name server (dns) and other routers on backbone of internet
these routers further conencted to: their own lans, other routers, servers

34
Q

web servers and clients

A

web servers carry out many functions - most common is:
hosting ebsites
dealing with client reuqests e.g http get requests for a page

the webpage stored as text is sent to browser which uses rules to render it correctly for user

35
Q

example of web server functioning

A

url request sent by browser made from user
browser sneds domain name to DNS
DNS maps domian name to IP addres and returns it to browser
GET request for webpage is sent to web server using IP address
requested webpage returned to clients web browser

36
Q

the cloud

A

servers can be used 2 store data and programs that can be accessed and used over the internet

this is the cloud

37
Q

avantages of lcoud

A

access any time anywhere from any device
large storage capacity
autmoatic backup
ez online collaboration

38
Q

how does a dns turn a url into an ip address

.com / google.com is example

A

url received by dns resolver server
server queries a dns root name server
root server responds w/ address of top level domain server for .com
resolver makes a reuqest to the .com TLD server
the TLD server responds w/ ip address of domains name server - google . com
recursive resolver sends query to domains name server
ip address google.com returned to resolver from name server
dns resolver then responds to web browser with ip addres of google.com

39
Q

the two toplogies

A

star
mesh

40
Q

def network topolgy

A

give arrangement of all elements needed for networking

41
Q

star netowrk toplogy

A

most popular wired network type
has a central switch
all devices conenct to central switch
switch is intelligent and makes sure traffic only goes where intended
if a single cable breaks only that comp affected
swithc is still a serious point of failure

42
Q

full mess network topology

A

every device connected t every other device
if a break in a connection you can still route traffic via another route
however lots more cabling and switch hardware required adding to cost for large networks

43
Q

partial mesh netowrk tololgy

A

multiple routes exist between different devices
every device not connected to every single other device
is a compromise solution which lowers amount of hardware needed compared to full mesh network

44
Q

what is the wired connection you should know in gcse spec

A

ethernet

45
Q

wireless connection to know

A

wireless
bluetooth

46
Q

what is chosen standard for implementing star network

A

ethernet.
with twisted pair cables, dublex communication is possible (sending and receiving data simultaneously)
CSMA/CD protocol is therefore not needed because frames dont collide

47
Q

can you use ethernet for mesh toplogies

A

yes.
however additional protocols for route finding between switches will be needed.

48
Q

ethernet
data is transmitted in frames which includes

A

preamble of bits used to synchronise transmission
start frame deliminator to signify start of data part of frame
source and destination of MAC address
actual data
error checking info (cyclic redundancy check - CRC)

49
Q

wireless networks (wifi)

A

popular because avoids need to install cables
portable connection
bandwidth is lower than in wired connection
secuirty is more of a problem than with wired connextion
ideal as running lotsof cabling through home is undesirable

50
Q

wireless networks (bluetoth)

A

ideal for connecting personal devices
very short range
ideal for connectig wireless keyboard to computer, or wireless headphones to a phone

51
Q

wifi vs bluetooth

A

wifi range: 100m
wifi bandwidth: high
power consumption: high

bluetooth:
range: 10m
bandwidth: low
pwr consumption: low

52
Q

encryption of wireless networks

A

wireless networks broadcast data so must be encrypted 2 b secure
done by scrambling data in cipher using ‘master key’ created from SSID of the netowrk and password
data is decrypted by receiver using same master key - key isnot transmitted

53
Q

protocols used 4 wireless encryption

A

WEP, WPA, WPA2

a handshaking protocol used to ensure receiver has valid master key before transmission to device begins

54
Q

do wired networks need encrption

A

though naturally more secure, it is still recommended to encrypt data on wired networks

55
Q

what does every NIC have

A

a Media Access Control address (MAC address)
used to route frames on a LAN

56
Q

what addressing method used for when LAN is connected to WAN

A

IP addressing - used to route frames on a WAN
frames on a WAN are called ‘packets’

57
Q

Internet Protocol Address

A

a unique number used to identify a host computer or node which communicates over IP on the internet

twoversions:
IPv4, IPv6

58
Q

IPv4 format

A

written as 4 numbers
seperated by periods
each number in the range 0-255
around 4bn addresses possible with IPv4

59
Q

two parts to IPv4 address

A

network idenidier
host identifier

network identifier is 3 bytes (is at beginning)
host identifier is 1 byte at the end

60
Q

Internet of Things

A

describes devices that connect and exchange data with other devices and systems over the Internet and other communication networks

61
Q

IPv6 format

A

16 bytes in size
written as 8 groups
seperated by colons
each group made up of 4 hex values represntig 16 bits

around 340 trillion, triollion, trillion combs

62
Q

standards in use

A

character sets: ascii, ex. ascii, unidcode
webpages and HTML
protocols to communicate on LANs and WANs
IEEE (standards for computer cables)
document image andsound standards (PDF, PNG, MP3)

63
Q

what are standards

A

a set of specifications for: hardware and software

64
Q

what do standards make possible

A

for manufacturers and producers to create products and services compatible ith each other

65
Q

key protocols

A

TCP/IP
HTTP
HTTPS
FTP
POP
IMAP
SMTP

66
Q

TCP/IP

A

transmission control protocol/internet protocol

used for communication over lans and wans.

TCP - provides error free transmission between 2 routers
IP - routes packets across a WAN

67
Q

HTTP(S)

A

hypertext transfer protocol (secure)

used for webpage requests

HTTPS has encryption and authentication - used for websites dealing with senstive info e.g banking sites

68
Q

FTP

A

file transfer protocl

used for file transfers, normally on a WAN

often ppl use ftp clients, software apps which sit on op of actual ftp protocl. you interact w/ program and it generates and sends appropriate FTP commands

69
Q

POP, IMAP and SMTP

A

used for email

POP - Post office protocol
IMAP - Internet message access protocol
SMTP - simple mail transfer protocol

used in conjunction w/ mail servrs
mail servers act like online post office
SMTP - transfes outgoing emails from one server to another/ from email client to server

70
Q

job of POP and IMAP

A

POP - retrieves emails from mail server. removes it from server and transfers it to your device
IMAP - same, but keeps emails on mail server to allow synchronicity beteen devices

71
Q

complexity of networking (data transfer)

A

data transfer must be split into smaller packets and frames
packets must be sequenced on arrival
packets must be sent between routers on a wan
frames must be sent between devices on a LAN
packets and frames must be error checked on arrival, and requested to be resent if necessary

72
Q

complexity of networking (transmission)

A

different cables used: fire obptic, twister pair, coaxial
wireless comms w/ frequencies and channels
simple and dublex transmissions

73
Q

complexity of networking (others)

A

different applications for different tasks: web pages, email, file transfer
encryption, security and authentication of users and data
connexion to remote servers and maintinaing open connextions
peer2per and client server models

74
Q

the concept of layering

A

to divide complex task of networking into smaller simpler tasks that work with eahc other
hardware and/or software for each layer has defined responsibility
each layer provides servcice tolayer above it

75
Q

avantage layering

A

reducses compleinty of problem into manageable sub problms
devices can be manufactured to operate at a partuicualr layer
products from different vendors will work together

76
Q

the layers

A

Application Layer
Transport Layer
Internet Layer
Link Layer

77
Q

application layer

A

GCSE Computer Science (5 decks)

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