The Internent Flashcards
1
Q
What is the Internet?
A
- A network of networks (worlds largest WAN)
- An infrastructure (Not content; not the WWW)
- Reliable
- independent of computer platforms
- Cheap (low power consumption)
- fast
2
Q
What are some of the uses of the Internet?
A
- Communication = eg; Skype and email. Devices can be controlled by signals sent over the Internet
- Information = eg; Wikipedia
- Entertainment = games, gambling, movies and music
- education = online courses and resources
- Financial = online banking
- control = devices can be controlled remotely via Internet links. (Smart houses)
- Commerce/advertising = online shopping
3
Q
What is bandwidth and what effect does it have?
A
- Number of bits of data that can be sent or received in a given time (Mbit/s)
- Higher bandwidths are needed to cope with increasing data demands such as movie streaming
- Availability is patchy
4
Q
What was the status of the Internet in the 1960’s?
A
- Circuit switching used to connect computers
- Defence Advanced Research Projects Agency (DARPA) developed plans to connect a small number of computers in the US
- There was concern that in the event of war communications between computers could be disrupted.
- Packet switching was developed and it was less liable to dislocation
- 1969 first connects made in ARPANET
5
Q
What was the ARPANET?
A
First network to implement the TCP/IP protocol suite
6
Q
What as the status of the Internet in the 1970’s?
A
- 1972 email was born
- Open architecture was born. Connectivity was enabled between diverse systems
- Connecting protocol developed to allow complete independence for each connected network
- TCP/IP developed and versions were available for individual PC’s
- DNS system developed
7
Q
What is the WWW?
A
- Collection of billions of web pages stored on servers around the world
- Pages are accessible anywhere, subject copyright and government restrictions
- Based on HTML, have hyperlinks and often include images, videos and other media
8
Q
What is HTML?
A
- Text based language that uses tags.
- Can produce basic web pages using any plain test editor
- Tags mark out elements on a web page to indicate to a browser how to display or process the element. (Displaying the text in a particular way or forming a link for example)
- links connect to other pages or same parts of the same page
- Applications can be embedded into HTML files (eg; flash)
9
Q
What are standards?
A
-ensure resources can be accessed and used by a wide variety of computers operating systems and applications
10
Q
Examples of common standards supporting and supported by the web?
A
- HTML = writes web pages for display
- HTTP = hypertext transfer protocol, client-server protocol for requesting and delivering resources such as HTML files
- CSS = define how HTML elements are displayed on a page. Stored separately from the files they affect
11
Q
Examples of file standards used on web pages?
A
- PDF = displays documents as intended
- JPEG = lossy compressed form of graphic storage
- GIF = lossless compressed image file format
- MPEG = compression standard for audio visual and data files
12
Q
What are web authoring tools?
A
- Environment for writing HTML (eg: Dreamweaver)
- Have split screen options where you can make changes in HTML file or in the design screen
- Include auto complete functions
- Common actions available from a menu
- Some dev’s may want tighter control over what code is produced and so will use an ordinary text editor
13
Q
What is CSS?
A
- Linked to HTML files, details how content from the web should be formatted
- changes in CSS cascade down to the HTML files linked to that CSS. One change in the CSS will be reflected in all associated web pages
- Makes editing websites much faster and easier
- eg: you can set all <h1> tags to be a certain font, colour weight and size
- Easy conversion from one scheme to another (important when developing a website for different platforms)
- </h1>
14
Q
What are the main HTML tags used?
A
Look in pictures for answer
15
Q
What is JavaScript?
A
- Scripting language that runs in browsers. Makes page interactive
- Used to write scrips that control the behaviour of web page elements. Run without need for plug-ins
- It is a high level and dynamically typed interpreted language
- Used for; loading page content, animating elements, validating web forms
16
Q
What are plug-ins?
A
- Software that adds a feature to an app
- Eg; browser plug-ins such as adobe flash player
17
Q
How is Java used in terms of the Internet?
A
- Used to write embedded applets to run in web pages
- Complied to bytecode that runs in a runtime environment. This needs to be present on computer in order to run Java applets
- Runs programs in an isolated sandbox which is intended to protect the computer from any damaging code
18
Q
What is bytecode?
A
-form of object code that is processed by a VM
19
Q
1) How would I use CCS directly inside elements to style a heading blue?
2) How would I style elements, class and identifiers in external style sheets
3) What are the main properties in CSS
A
Answer in photos
20
Q
How do you write the following in JavaScript?
1) Variables
2) If statements
3) what does == mean and what does === mean
4) outputs (alert, writing and changing)
5) Incrementation
6) comments
7) String manipulation
8) Functions
9) Arrays
A
Look on photos for answer
21
Q
Why do we compress files?
A
- decrease file sizes
- Increase download/transfer speed
22
Q
What is lossy compression?
A
- Used for photos/video/audio
- data is removed from original file
- no NOTICEABLE lack in quality
- Cannot get data back from decompression
23
Q
What is lossless compression?
A
- condenses info stored
- no less of data
- If an item is repeated in a file it is stored once and along with the amount of repetitions
- Original file can be regenerated
24
Q
What do search engines do?
A
- build up indexes of websites that can be searched quickly by various search algorithms
- early versions required site owners to notify the engines but later various robots known as “spiders” searched for sites by “crawling” over websites and indexing the words found there. “Webcrawler” first example of this
25
Q
How do modern search engines function?
A
- search internet for various keywords
- index these with links to where they can be found
- this index is made available to all users
- can cope with misspellings and provide searches in various languages
- make use of meta tags: extra info that web designers add, but do not display, to make it more likely to be found
26
Q
What is the pagerank algorithm?
A
- Shows the user the most useful websites based on their search. RECURSIVE PROCESS
- Used by google. It ranks possible web pages according to external links
- if a web page has many links into it from other pages (votes) it is deemed to be popular and more worthy of consideration
- not all votes are equal. Some votes more important than others. (This is based on the rank of these pages)
27
Q
What is the equation of the pagerank algorithm?
A
- PR(A) = (1-d) +d (PR(T1)/C(T1) + …. +PR(Tn)/C(Tn))
- PR(A) is the pagerank of page A
- PR(Ti) is the pagerank of pages Ti that link to page A
- C(Ti) is the number of outbound links on page Ti
- d is the damping factor that can be set between 0 and 1
28
Q
What is damping factor?
A
- reduces the ranking on the assumption that a typical surfer will eventually give up clicking and resents the probability that the surfer will continue
- set to 0.85
29
Q
How does google maintain the pagerank algorithm?
A
- each time the google spider crawls the web, it recalculates the rank
- original algorithm is prone to abuse by those who set up ‘link farms’ to artificially increase the number of links to favoured pages. Google continues to alter its algorithms to circumvent such problems
30
Q
What make up the basis of most web interactions?
A
- interactions between client and web server which holds resources the client wants
- resources can be static or involve multiple transactions (such as making a booking)
- decisions have to be made about what processing occurs where. Issues are to do with performance and security
31
Q
What are the pros for client-side processing?
A
- Reduces load on the server; the server may be busy handling multiple transactions and if some of the processing can be offloaded to client machines, this will speed up activity
- user will have better experience if data input is checked there and then without the delays of immediate sending of each item to the server for checking
- reduces web traffic; if input data can be validated by a client-side script, this will reduce the likelihood of erroneous data being sent for the server to validate and process
32
Q
What are the pros for ever-side processing?
A
- Data validated by a client-side script may have problems with it; it is still necessary to have further validation at server end
- essential for actually querying a DB. It is vital to keep the data owned by an organisation secure, so any processing of that data must take place under the control of the organisation. Therefore SQL processes will largely have to be located at the server end. No sensitive data should be send to the client where it could be intercepted and manipulated
33
Q
What is Dictionary encoding?
A
- the compression algorithm builds an index where each data item is recorded along with an index reference
- the compressed file then consists of the dictionary plus the sequence of occurrences
34
Q
What is run-length encoding?
A
- makes use of redundant data, so that if a data item occurs multiple times, the item is stored once in an index along with the number of repetitions
- eg; part of an image with many blue pixels old be stored in an index by storing the start location and the number of reps
35
Q
What type of actives require high levels of encryption?
A
- online banking payments
- communications involving trade secrets or other sensitive or personal data
36
Q
What is encryption?
A
- existed for as long as there has been communication
- Ciphers used to protect data and the key is needed to return data back to original state (decryption)
- keys can be applied in various ways and can be numbers, words or random strings
37
Q
What is symmetric encryption?
A
- key used to encrypt message is also used to decrypt it
- both sender and recipient need to know key
- some algorithms encrypt one byte at a time whereas others take a whole block of data and pad it to make units of a fixed size
- key may be used multiple times or it may be generated for each transaction
- danger of a successful attack on symmetric encryption messages, either by intercepting the key or duplicating the key-production process
38
Q
What is asymmetric encryption?
A
- requires use of 2 different keys
- key used to encrypt is not the same as they key used to decrypt
- encrypt key is publicly known and can be used by anyone who wants to send an encrypted message via a publicly known algorithm
- the algorithm is implemented using the second, compatible but secret, private key
- to decrypt the message the public algorithm is applied with the secret key. Safer but requires more processing power.
- keys are typically large random numbers that are unlikely to be guessed
39
Q
What are hash functions used for?
A
- cam be used to store and check passwords, commonly used for network logins and online transactions. Hash value is used to store password in sever
- it is easy to transform plaintext message or password into something else, but very difficult to regenerate the plaintext (or password) from the hash value. If DB is hacked passwords are still secure
- Next time user logs in, the Password is transformed using hashing algorithm and result is looked up to see if it matches stored hash value. If it does access is granted
- no use for sending messages that need to be decrypted.
40
Q
What is a brute force attack?
A
- method of hacking where every possible combination of characters is tried one by one
- computationally expensive and encryption is designed to make it too much trouble to spend the effort
41
Q
What are other methods used by hackers except brute force?
A
-common passwords stored in a dictionary and tried out along with hashing algorithms
42
Q
What is “adding salt”?
A
- the salt is a random string appended to a new password before hashing.
- makes the hash value different even for the same password
- salt is stored alongside the hash value. To check the password the salt is used to decrypt the hash
43
Q
What is a dynamically typed language?
A
Language that does not need a prior declaration of variables before use and creates one when needed during the running of the programme, assigning a data type according to what value is passed to it
