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Computer Science > Unit 5 Networks And Web Technologies > Flashcards

Unit 5 Networks And Web Technologies Flashcards

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1
Q

Internet Service Providers

A

Connects directly to this backbone and distribute the Internet connection to smaller providers who in turn provide access to individual homes and business.

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2
Q

Uniform Resource Locators

A

A Uniform Resource Locators is the full address of an internet resource. URLs are used to specify the means of accessing a resource across a network and its location. The protocol and the domain name of the resource together form the URL

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3
Q

Domain Name System (DNS)

A

DNS servers are dedicated computers with an index of domain names and their corresponding IP addresses.

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4
Q

DNS server structure

A
  • There are 13 root DNS servers that work together to catalogue every domain name
  • These are segmented into geographical groupings or levels
  • When the IP address of a given domain is not known it is referred to a related domain server that may know
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5
Q

Internet Register

A

Internet registrers hold records of all existing website names and the details of those domains that are currently available to purchase

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6
Q

Internet Protocol

A

IP address is a unique address that is assigned to a network device. It indicates where a packet of data is to be sent or has been sent from. Routers can use address to direct the data packet accordingly.

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7
Q

LAN

A

Local Area Network (LAN) is a network spread over a ​small geographical area

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8
Q

WAN

A

Wide Area Network (WAN) is a network spread over a ​large geographical area​, that
typically requires ​extra hardware

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9
Q

DNS

A

● Domain Name System
● The system given to the ​method of naming internet resources
● A hierarchy where each smaller domain is separated from the larger domain by a
full stop
● DNS server translates domain names into IP addresses when we access a website.

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10
Q

Bus topology

A

Network topology where all ​terminals ​(devices) are connected to a
backbone cable

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11
Q

Advantages of Bus Topology

A

Cheaper to set up, doesn’t require any

additional hardware

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12
Q

Disadvantages of Bus Topology

A

If ​backbone cable fails​, the entire network gets disconnected
As traffic increases, ​performance decreases
All computers can ​see the data transmission

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13
Q

Star Topology

A

Uses a central node (​switch/computer​) to direct the flow of data

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14
Q

Advantages of Star Topology

A

Performance is ​consistent​ even if network is being ​heavily used
If one cable fails,​ only that station is affected
Transmits data faster​, so it gives better performance than bus topology
It’s easy to add new stations
No data collisions

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15
Q

Disadvantages of Star Topology

A

Expensive​ due to switch and cabling

If the central ​switch fails,​ the rest of the network fails

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16
Q

Mesh Topology

A

Every node is connected to every other node

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17
Q

Advantages of Mesh Topology

A

No cabling cost
As nodes increase, the ​reliability and speed​ of network becomes better Nodes ​automatically get incorporated
It’s ​faster​ since nodes don’t go through a central switch

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18
Q

Disadvantages of Mesh Topology

A

You have to purchase devices with wireless capabilities

Maintaining the network is ​difficult

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19
Q

Circuit switching

A

It involves creating a communication connection between two endpoints for the duration of a phone call or transfer of data

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20
Q

Packet switching

A

Packets are often sent across networks that have multiple connections with multiple routes through to a destination

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21
Q

Data packets

A

When sending across a network, data is broken into chunks (units) called data packets and assembled again at the receiving end

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22
Q

Routing

A
  • Routers forward data packets from one network to another
  • Each router stores data about the available routes to the destination node
  • Looks up the destination IP address in its routing table to find the best router to forward the packet to
  • Each transfer between routers is known as a hop
  • Routers continue to forward the packet until it reaches its destination node
23
Q

Gateways

A

• A gateway is required where data is travelling from one network to another that use different protocols

24
Q

Circuit Switching advantages

A

The data arrives in a logical order which results in a ​quicker reconstruction​ of the data.

This enables two uses to hold a call without delay​ in speech.

25
Q

Circuit switching disadvantages

A

Bandwidth is wasted during periods of time where no data is sent.

The devices must transfer and receive data at the ​same rate​.

Since switches are used, electrical interference is produced which can corrupt​ or ​lose data​.

26
Q

Packet Switching advantages

A

There are multiple methods to ensure data arrives (check ​Checksum and ​Cyclic Redundancy Check​).

There is more than one method of getting to the other devices, so if one path breaks you can use another.

You can transfer packets over ​very large networks​ to allow communication globally.

27
Q

Packet Switching disadvantages

A

Time is spent deconstructing and reconstructing the data packets.

28
Q

Application Layer

A

. Based at the top of the stack
. Specifies ​what protocol​ needs to be used in order to ​relate the application that’s being sent
. Uses protocols relating to the application being used to transmit data over a network, usually the internet
. For example, if the application is a browser then it would select a protocol such as HTTP, POP3, FTP

29
Q

Transport layer

A
  • Uses the Transmission Control Protocol (TCP) to establish an end‐to‐end connection with the recipient computer
  • Splits data into packets and numbers them sequentially
  • Adds port number to be used based on HTTP protocol
  • At the receiving end this layer confirms that packets have been received and requests any missing packets be resent
30
Q

Internet layer

A

Uses the Internet Protocol (IP) to address packets with the source and destination IP addresses
• A router forwards each packet towards an endpoint called a socket, defined by the combination of IP address and port number: 42.205.110.140:80

31
Q

Link Layer

A

The ​connection between the network devices

Adds the ​MAC address​ identifying the ​Network Interface Cards​ of the source
and destination computers

32
Q

On the recipient’s computer the layers occur again in reverse:

A 
○ Link Layer
■ Removes the MAC addresses 
○ Network Layer
■ Removes the IP addresses 
○ Transport Layer
■ Removes the port number and reassembles the packets 
○ Application layer
■ Presents the data to the recipient in the form it was sent
33
Q

Firewalls

A

● Devices designed to ​prevent unauthorised access​ to a network
● Consist of two network interface cards (NICs), in-between the user and their internet connection.
● Perform packet filtering / static filtering
○ Limit network access​ in accordance with ​administrator rules​ and policies

34
Q

Client-Server

A

● Client-Server networks have ​terminals​ known as clients connected to a ​server
● The server is just a​ powerful central computer
● The server holds all of the ​important information​ and has ​extra processing power and the clients can request to use it

35
Q

Advantages of Client-Server

A

● More ​secure
● Central backups ​eliminate the need for client backups
● Sharing data and resources between clients

36
Q

Disadvantages of Client-Server

A

● Expensive​ to set up

● Staff with training are required to maintain the server

37
Q

Peer-to-Peer networks

A

● Computers are​ connected to each other​ so that they can share files
● Inexpensive ​to set up
● Allow users to ​share resources
● Easy to maintain

38
Q

Proxy Server

A

• A proxy server makes a web request on behalf of your own computer, hiding the true request IP addresses from the recipient

39
Q

Functions of a proxy server

A
  • Enables anonymous surfing
  • Can be used to filter undesirable online content
  • Logs user data with their requests
  • Provides a cache of previously visited sites to speed access
40
Q

Encryption

A

The act of encoding a plaintext message so that it cannot be deciphered unless you have a numerical key to decrypt it
• If the message is intercepted it cannot be understood
• If the key can be intercepted, the encryption process is rendered useless

41
Q

Worms

A

A worm is a standalone program that does not require a user to run it in order for it to spread.
• Worms exploit vulnerabilities in the destination system and spread automatically

42
Q

Trojans

A

Trojans are malicious software programs that masquerade as innocuous or useful applications
• They cannot self-replicate
• Often they serve to open up back doors in your computer to the Internet so that the processing power, Internet bandwidth and data can be exploited remotely

43
Q

Phishing

A

Phishing is using email to manipulate a victim into visiting a fake website and giving away personal information

44
Q

Code quality

A
  • Improving code quality, together with monitoring attempts to gain unauthorised access and protection can significantly reduce threats from malware
  • Measures include:
  • Guarding against buffer overflow attack
  • Guarding against SQL injection attack
  • Use of strong passwords for login credentials
  • Two-factor authentication
  • Use of access rights (file system permissions)
45
Q

Buffer overflow

A
  • Buffer overflow occurs when a program accidentally writes data to a location too small to handle it
  • As a result the overflowed data (written to location #3 below) may end up in a neighbouring instruction space
  • Malware can deliberately cause and manipulate overflow data which may then be read as a malicious ‘instruction’
46
Q

HTML

A

● HTML is the ​language/script​ that ​web pages​ are written in,
● It allows a browser to ​interpret​ and ​render​ a webpage for the viewer by describing
the​ structure and order ​of the webpage.
● The language uses tags written in ​angle brackets​ (, ) there are two
sections of a webpage, a body and head.

47
Q

CSS

A

● CSS is a ​script/language​ like HTML except is used to ​describe the style​ of a
webpage.
● CSS can be used to specify the way HTML elements look, they can be applied to
whole tags such as <h1>, </h1><p> or </p><div>.
● CSS can be used using two different form, internal/embedded or external CSS the
internal CSS is when the style is placed.
● The ​internal/embedded CSS​ is placed inside the style tags and is ​entered directly
within the HTML document.</div>

48
Q

JavaScript

A

● JavaScript is a language which has a similar layout to languages like ​python​. The
main function of JavaScript is to add ​interactivity​ to websites.
● JavaScript isn’t ​compiled​, instead it is ​interpreted​, this is so it can be interpreted in
the browser every time the webpage is displayed.
● Javascript be used to ​input data​ on the ​client’s computer​, this may change the local
page interactively or post data to a server. The advantages:
○ The local computer can fix invalid data before sending it off to the servers,
○ It can ease the traffic off of the busy servers,

49
Q

Classes and Identifiers

A 
● Class and identifier selectors are the names which you style, this means groups of
items can be styled, the selectors for html are usually the div tags.
● Identifiers are defined with an initial hashtag, and must be unique to each webpage.
● Classes are defined with a full stop as a prefix to the class name, classes can be
used multiple times on a webpage.
50
Q

Network

A

A ​network​ is the name given to ​two or more​ computers connected together with the ability to ​transmit data​ between each other. There are two main types of networks: ​local area networks​ and ​wide area networks.

51
Q

HTTP (Hypertext Transfer Protocol)​

A

Used for web page rendering, an encrypted version, ​HTTPS (Secure)​, is becoming more common

52
Q

TCP/IP​ ​(Transmission Control Protocol / Internet Protocol)

A

This is a networking protocol used in the routing of packets through networks

53
Q

POP3 (Post Office Protocol)​ and ​IMAP (Internet Message Access Protocol)​

A

Mailing protocols, used for email access.

54
Q

FTP (File Transfer Protocol)​

A

Used for the transmission of files over networks.

Computer Science (12 decks)

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