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1.3 again Flashcards

1
Q

advantages of having a network

A

-users can share peripherals
-access files from any computer
-easier communication
-share files easily
-centralised backups, updates and security

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2
Q

disadvantages of having a network

A

-cost from additional equipment
-malware - easily spread on unsecure network
-specialist staff required
-hacking - data can be accessed without permission, increased security risk

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3
Q

what is a local area network

A

a network which :
-has a small geographical area
-hardware used is owned by the company using it
-(uses UTP, fibre optic of wireless)

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4
Q

what is a wide area network

A

a network which:
-covers a large geographical area
-hardware used to connect networks is not all owned by the company, usually telecom companies
-(connects LANs to form a WAN)
-(uses fibre optic, telephone lines and satellites to connect WANs)

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5
Q

5 factors that affect how well a network performs

A
  1. number of users
  2. bandwidth
  3. latency
  4. error rate
  5. transmission media
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6
Q

how does number of users affect the performance of a network

A

-more data is being transmitted at the same time
-bandwidth is split between the devices, less bandwidth per device
-devices must wait longer before transmission

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7
Q

what is bandwidth

A

the amount of data that can be sent and received at any given time

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8
Q

how does bandwidth affect network performance

A

-less data can be sent and the network can slow down

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9
Q

latency

A

delay between data being sent and received

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10
Q

how does latency affect performance

A

-more data will be on the network causing collisions
-data takes longer to be sent and received

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11
Q

error rate

A

measure of how many packets of data do not reach their destination

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12
Q

how does error rate affect performance

A

-less reliable connections have greater error rates
-data has to be resent often

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13
Q

transmission media

A

the type of cable used in wired connections

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14
Q

how does transmission media affect performance

A

some media have higher bandwidth than others:
wired>wireless
fibre optic>UTP

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15
Q

what is a network model

A

the logical structure of the network

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16
Q

what is a client server model

A
  • a computer is either a server or a client, all clients are connected to the server via a switch
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17
Q

what do servers do

A

-Managing access to the Internet (files, programs and web)
-Managing printing
-Providing email services
-Providing backups
-Controlling security

servers are often more powerful than client machines

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18
Q

advantages of client server models

A

-managing backups are easier (centrally)
-updating and installing new software is easier (centrally)
-security of files easily managed

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19
Q

disadvantages of client server models

A

-servers are expensive to purchase, setup and maintain
-specialist required
-servers are a single point of failure

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20
Q

what are peer to peer models

A

-a peer is a computer on a network and is equal to all other computers
-each peer:
-have their own peripherals
-provide access to their own files
-responsible for backups (carrying out and storing), security

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21
Q

advantages of peer to peer models

A

-easy to setup and maintain
-cheap as no expensive hardware
-no specialist required

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22
Q

disadvantages of peer to peer networks

A

-own backups must be managed
-own software updates must be managed
-can be less secure

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23
Q

hardware required in a LAN

A

router
wireless access point
switch
network interface card
transmission media

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24
Q

role and tasks of the router

A

-receives and transmits data packets between networks
-assigns IP addresses to the nodes
-connects LANs to a WAN
-identifies the most efficient path to the destination
-manages prioritises data traffic
-converts packets from one protocol to another

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25
wireless access point
-allows wireless devices to connect to a LAN -connects to a switch (or router) via an ethernet cable -limited range so multiple WAPs can be used for complete coverage
26
role of a switch
-connects devices together in a LAN -receive and direct data packets to its destination -creates a list of devices connected to it as it receives signals -use MAC addresses of devices connected to it -(contains extra software to allow administration)
27
network interface card
allows the computer to connect to a network -can be both wired or wireless and allows computer to send and receive data over a network
28
3 types of transmission media
-UTP -coaxial -fibre optic
29
UTP
-made of insulated pairs of copper wires twisted around each other -low bandwidth and more affordable
30
coaxial
-medium bandwidth and medium price -connect large scale networks like telephones
31
fibre optic
-high cost and high bandwidth -unaffected by electrical noise, making it fastest -used for long distance connections e.g. between countries
32
what is the internet
-a collection of networks spanning the whole world -WAN
33
how does domain name system work (full details)
1. URL entered into web browser 2. web browser sends a query to a DNS (hosted by ISP) to translate URL into an IP address 3. DNS Resolver checks its cache to see if it has the IP address for the domain, if not it sends it to the DNS root servers 4. the root server directs the resolver to a top-level domain based on the extension of the URL 5. TLD server provides resolver with IP address of the domain's authoritative DNS server 6. DNS server responds with the IP address for the requested domain 7. web browser sends a HTTP or HTTPS request to the IP address it received 8. The server at the IP address processes the request and sends back the data for the web page (HTML, CSS etc) 9. the web browser renders the received data into the web page that you see
34
how is a URL converted into IP address (3)
-request sent to DNS for URL -DNS looks up the IP in its database -DNS returns IP -if not found, the DNS sends to higher level DNS (if not found return an error)
35
what are web servers
-dedicated servers that store web pages and other resources -have dedicated IP address to ensure that users can access them 24/7
36
what are clients
end users who make requests of web servers
37
hosting
-the storing of websites, files and other content on servers -available 24/7 -same IP address for the server so the user can access the website always
38
cloud
a collection of servers which are used to store data, applications and files over the internet
39
advantages of using the cloud
-content can be accessed anytime from anywhere -(users can use any device to access their content) -large storage capacity available them them without any additional hardware -low cost -responsibility for backups and security is with the cloud service provider
40
disadvantages of using the cloud
-constant internet connection is needed -vulnerable to security threats -not clear to users who is the owner of data once uploaded to a cloud service -reliant on third party for back up and security procedures
41
URL
uniform resource locator: the web address types into a web browser
42
what is a network topology
the physical structure of the network
43
star topology
central switch which all other devices connect to
44
advantages of star
-failure of one cable or node does not affect other nodes -new nodes are easily added by just connecting to the switch -higher performance as data is only passed to the intended recipient, fewer collisions -improved security as data packets are not sent to other devices
45
disadvantages of a star network
-central switch is a point of failure -can be expensive if wired
46
mesh topology
all computers are connected to all other computers (full mesh) (partial mesh is not fully connected)
47
advantages of mesh topologies
-cable is not a central point of failure, data packets can take alternative routes -new systems can be added without disrupting the entire topology -can be quick if route to recipient is short
48
disadvantages of mesh topologies
-expensive and difficult to set up new devices due to number of connections -maintenance required for number of connections
49
what is ethernet
-a wired networking standard to carry electrical signals between devices -commonly used with twisted pair cables for duplex communication
50
advantages of wired networks
-fast data transfer -better physical security -longer range -less susceptible to interference (same as range)
51
disadvantages of wired networks
-cannot move easily -costs money to add new devices -trip hazards -limited number of devices -not compatible with all devices
52
wireless networks
network where connections are made using radio waves to transmit data through the air
53
advantages of wireless networks
-cheap and easy to add new devices, more devices can connect -can move around, portable -cheaper to setup -no trip hazards -more compatible
54
Wi-Fi
-standard for wireless networks -devices communicate with a WAP
55
advantages of wifi
-easy to move around -cheap to setup -compatible with most, devices have a built in wifi adapter
56
disadvantages of wifi
-slower data transfer than Ethernet -less secure than Ethernet, data can be intercepted -relies on signal strength to the WAP, signals can be obstructed (100m) -high power consumption
57
what is bluetooth
-a standard for wireless networks -used for a direct connection between two devices
58
advantages of bluetooth
-low power consumption
59
disadvantages of bluetooth
-slow transfer speeds -insecure, data can be intercepted -short range
60
what is encryption
scrambling data before being transmitted across a network to protect the contents from unauthorised access
61
how is wireless data encrypted
-wireless networks are identified by a service set identifier, which along with a password is used to create a master key -devices are given a copy of the master key when connected to the network -key is used to encrypt data into cipher text before being transmitted -the receiver uses the same key to decrypt the cipher text back to plan text -master key is never transmitted
62
example of a protocol for wireless/Wi-Fi security
WPA2
63
how is wired data encrypted
same as wireless but individual applications decide how encryption is used, e.g. HTTPS
64
IP address
-unique identifier given to devices which communicate over the internet -allows data to be delivered to the right device
65
what does it mean by IP addresses are dynamic
they can change, connecting to a different network will change the IP address
66
IPv4 format, # of combinations
4 denary numbers between 0 and 255, separated by full stops, 4 bytes in total 2 to the 32 (over 4 bn) unique addresses, too little
67
IPv6 format and # of combinations
8 blocks of 4 hexadecimal digits, separated by colons, 16 bytes in total 2 to the 128 addresses
68
MAC addresses
unique identifier given to devices which communicate over a local area network make is possible for switches to efficiently forward data to the intended recipient
69
what does it mean by static MAC addresses
MAC addresses cannot change
70
when are MAC addresses assigned
during manufacturing, with the NIC
71
MAC address format. # of combs
12 hex digits, grouped in pairs, 48 bits first three pairs are the manufacturer ID, last 3 pairs are the serial number of the NIC 281 trillion unique addresses available
72
differences between MAC addresses and IP addresses
IP can change, MAC cannot IP communicates over a WAN, MAC for LAN
73
what is a standard
a set of guidelines that when used with different hardware and software allows them to work with each other and allow data exchange
74
why are standards used
allow manufacturers and SWE the ability to create hardware and software that will function together
75
what are protocols
a set of rules that govern communication on a network
76
TCP/IP protocol, and what each one does
allows communication over the internet TCP makes sure communication between two routers is error free IP makes sure data is delivered to the right device on a WAN
77
HTTP and HTTPS
allows communication between clients and servers for website viewing (allows clients to receive and send data to the server) HTTPS has an added layer of security, all data is encrypted
78
FTP
allows sending and receiving files between computers uploads files to and from a web server
79
SMTP
allows communication between an email sender and the emails server and between different email servers using the internet
80
POP
protocol for downloading emails to a device from an emails server email is removed from server after being retrived
81
IMP
protocol for downloading emails to a device from an email server a copy is retained on the mail server after the email has been retrieved
82
advantages of POP
-frees up storage space on email servers -faster on slow connections
83
disadvantages of POP
-only access emails from the device they are downloaded to -emails deleted on the server once downloaded
84
advantages of IMAP
-view and manage emails from any device with internet access -changes made on one device are synchronised on all connected devices
85
disadvantages of IMAP
-server storage space can limit amount of retained emails -requires internet access to view emails
86
what is a layer
a sub part of a more complex task, it is a division of network functionality
87
advantages of layers
-self contained, allows different developers to concentrate on one aspect of the network -a layer can be taken out and edited without affecting other layers, promoting interoperability between vendors and systems
88
Disadvantages of wireless networks
-prone to interference -less bandwidth -less secure -less range

Computer Science (16 decks)

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