Theory 9 The Internet and its uses Flashcards
What is the Internet and what is a protocol?
A global network of computers which includes smartphones, laptops, games consoles, IoT devices etc.
Standardised using TCP/IP: a protocol which allows networks to talk to each other.
Protocol: a specific set of rules used communication
All transmissions, worldwide, must follow the rules in order for the transmission to be successful.
What is the World Wide Web?
A set of interconnected web pages which a web page can contain text, images, video, animation and sound.
You access a web page by typing its URL (Uniform Resource Locator), e.g. https://www.st-albans.herts.sch.uk/
Hyperlinks allow web pages to link to each other.
What is a URL?
Uniform Resource Locators
A website address
You can also access a webpage by a hyperlink and from a result in a search
Identify each part of this URL: https://www.st-albans.herts.sch.uk/webpages/about.html
- Https : protocol
- St-albans.herts.sch.uk : domain
- Webpages : folder / location
- About.html : web page
Advantages of URLs
Easy to remember
Easy to type
The name usually means something
The geographic location is usually indicated
Disadvantages of URLs
Not the actual physical address of anything
The domain name server needs to be kept updated.
What is the HTTP Protocol?
The http protocol manages the transmission via the internet. It works as a request-response protocol and stateless protocol. Sessions are maintained using cookies.
https is secure and uses public-private key encryption
What is a Browser?
A browser is a program that allows you to visit a website, retrieve and display the information on a remote webpage
It:
* Displays (render) remote webpages
* Interprets HTML documents
* Translates embedded scripting, e.g. JavaScript
* Provides functions such as bookmarks and history
* Stores and retrieves cookies
* Makes use of plugins to play video, for example
* Uses a variety of protocols such as HTTPS as well as HTTP
* Provides navigation tools and an address bar
What are cookies?
Cookies are small text files stored on your computer by a website that you have visited. They are used for:
* Login information
* Information suitable for advertisers to use
* Customised webpage details
* Shopping basket contents and one-click purchasing
* Distinguishing between new and repeat visits
State and explain the two types of cookies
Session cookies
* A session is a single interaction with a website
* Session cookies are only stored for a single session
* Then they are replaced the next time you visit the website
Persistent cookies
* These are created the first time you visit a website
* They are kept until they expire
Advantages of cookies
Remembers data between visits
Disadvantages of cookies
- Privacy issues - you are being tracked and may be targeted by adverts based on your history
- Other users of your computer may be able to work out your interests
Not inherently secure but data can be encrypted
- Other users of your computer may be able to work out your interests
What do you need to connect to the internet?
- A web browser
- Computer
- Internet connection
- Modem and router (often incorporated into one unit)
An internet service provider (ISP) e.g. Virgin Media, BT
What is a modem?
A modem receives signals from your Internet Service Provider ( ISP ) through phone lines, optical fibre or coaxial cable and converts them to a digital signal.
What is a router?
A router creates a network between the computers in your home and forwards traffic between the internet and your computers. The network might be wired (ethernet cables) or wireless.
What is an ISP?
An ISP allows your devices to connect to the internet. They:
* Provide a router / modem
* Monitor your usage
* Give you an IP address
* Determine allowed bandwidth
* Provides security services e.g. some blocking of malware
Help you find web pages on the internet using DNS (domain name servers)
What are web pages?
Websites are hosted on webservers. These are:
* A computer with special server technology
* Connected to the internet
They process requests from clients which are usually made up of browsers requesting webpages.
What are IP addresses?
Every computer on the internet has a unique public IP (IPv4) address. Your home IP address is likely to be dynamic, meaning that it changes frequently. You can pay for static IP addresses but this only really done by large companies.
Within your home you have private IP addresses which are unique within your home, e.g. 192.168.0.1
There are two formats: IPv4 and IPv6
IPv4 is the older format and is made up of 4 bytes per IP address. They are written using decimal with dots in between the different parts, e.g. 172.16.254.1
IPv6 is the newer format and are written as hexadecimal separated by colons, e.g. 2001:db8::8a2e:370:7334. IPv6 was created to replace IPv4 as it provides many more IP addresses.
Advantages of IP addresses
- It is a location-based address
It can be split using bit masks to extract particular elements
Disadvantages of IP addresses
- Hard to remember
- Doesn’t mean anything to you
- Not tied to specific geographic locations
It can change
What are MAC addresses?
Permanent physical identifier of an electronic device connected to a network
Not the location of a device, the identification of a device
It is unique, worldwide across all networks and cannot be changed.
Advantages of MAC addresses
- Unique
- Can be used to block/allow devices (black list / white list)
Disadvantages of MAC addresses
- Hard to remember
- Doesn’t identify the network, user or location
- If the device is changed, the MAC address changes
- No way of associating with a domain (www.bbbc.co.uk) or an IP address. Domain name servers do this for IP addresses.
What is DNS?
The Domain Name System (DNS) is a protocol which translates user-friendly domain names (e.g. abc.co.uk) to IP addresses (e.g. 212.58.244.23)
This allows you to access a web page using a familiar URL and not worry about the actual IP address of the webserver.
