2.3 Internet Principles of Operation Flashcards
Cookies
A small data packet sent from a website and…
- …STORED in a user’s WEB BROWSER while the user is browsing that website.
- Every time the user loads the website, the browser sends the cookie back to the server to notify the website of the user’s previous activity.
- can store passwords, credit card details, address so that they no need to be re-entered in the future
- to track what the user has viewed on the website, so that the owner of the website can send them adverts that match their preferences
TCP/IP
- TCP (Transmission Control Protocol) controls how data packets are transmitted along Internet connections
- IP (Internet Protocol) makes sure data packets are sent to the right IP address
Internet Protocol (IP) address
- A unique address used to identify each device connected to the internet
- 32-bit number (4 bytes)
- allocated by the network/ISP
- can be used in place of URL
- can be IPv4 or IPv6
- can be static, meaning it doesn’t change each time a device is connected to the Internet
- can be dynamic, meaning it can change each time a device is connected to the Internet
Media Access Control (MAC) address
A unique number that identifies a device connected to the Internet
- 48-bit number (6 bytes)
Difference between IP address and MAC address
A device’s IP address is used to route data across the Internet to its LAN, then its MAC address is used to switch data across the LAN to the device itself
Computer network
A group of computers linked together to allow them to share resources (hardware, software, data etc.)
The Internet
A network of networks that covers the whole world
10 roles of an Internet Service Provider (ISP)
- Provide access to the internet
- Usually charge a monthly fee
- Monitor usage
- Give users an IP address
- Determine bandwidth
- Supports domain names
- Provide security services
- Provide web hosting facilities
- Provide access to Email
- Provides online data storage
4 things a computer must have to be connected to the Internet
- An ISP
- A modem or router (wired/wireless)
- Internet software, ie. web browser or app
- Shared protocols, eg. TCP/IP
Web page
A multimedia document that you can read over the Internet; it is created in a format called HTML
Website
A collection of web pages, stored on a web server
Web server
A web server hosts web page (holds the content of the web page in its storage). It will send the contents of the web page along an Internet connection to another computer.
Web browser
- Software that allows a user to display a web page on their computer screen
- Interprets/translates the HTML document
- Provides functions, such as bookmarks and history
How does a web browser work?
- Gets the web server’s name from the URL to connect to the web server
- Web server transfers a copy of the web page onto your computer
- Inteprets the HTML code and displays the web page so that you can interact with the content
Hyperlink
A piece of text or image (eg. button) that opens a new page in your browser when you click on it
HTTP
Hypertext Transfer Protocol is the protocol that makes hyperlinks work
HTTPS
HTTP secure. It has extra features, compared to HTTP:
- Authentication (checking that websites are not fake)
- Encryption (so nobody can see what you send to a website)
Protocol
A protocol is a shared standard/set of rules for communication
Domain Name System (DNS)
A directory of all the domain names in the world; the DNS matches domain names to their IP addresses
Hypertext Markup Language (HTML)
- a mark-up language used to create web pages
- translated by a web browser to display web pages
- uses (opening and closing) tags to format content
What is a markup language?
A markup language is used to add descriptions (tags) to pieces of text in a document
How does the web browser use the URL to access the web page?
- The web browser sends URL to DNS
- DNS stores an index of URL and matching IP address
- DNS searches for URL to obtain the IP address
- IP address sent to web browser, (if found)
- Web browser sends request to IP of web server
- Web server sends web page to web browser
- Web browser interprets HTML to display web page
- If URL not found DNS returns error
HTML structure + example
Instructs how the LAYOUT of the content of the web page is displayed
Example: placing an image alongside some text
HTML presentation + example
Instructs how the content of the web page will be FORMATTED, eg. colour (applied to some text)/style/CSS
Describe the use of structure and presentation in a HTML document.
- Presentation is used to format colour/style
- Structure is used to create layout
- In a HTML document structure and presentation are often kept separate
- By keeping the presentation separate it is easier to update colour/font
- Presentation is often stored in a file called a CSS …
- … the CSS in then linked to the HTML document to implement the presentation requirements
- (Mark-up) tags are used to define the structure of the document …
- … presentation and formatting can also be included within the tags
State what is meant by a URL.
- Uniform Resource Locator
- the website’s address
- user friendly version of the IP address
