3.7: The Internet
Eduqas / WJEC
What is the internet?
The internet is a global network of interconnected networks.
The world wide web (WWW) is not the same as the internet. It is a way of accessing information, using protocols such as HTTPS to view web pages.
What is a web browser?
A web browser is software that uses the HTTP or HTTPS protocol to access and display web pages.
Popular web browsers include Google Chrome, Mozilla Firefox and Microsoft Edge.
What is a URL?
URL stands for Uniform Resource Locator.
Web pages are accessed by typing a URL (a web address) into the address bar of a web browser. The URL is the complete address that matches an IP address where the website is stored.
We use URLs because they are easier to remember than IP addresses, for example, 'twitter.com' is simpler than '22.214.171.124'.
What is the structure of a URL?
A URL is structured into different segments:
What is a DNS Server?
A DNS (Domain Name System) server stores a list of domain names and a list of corresponding IP addresses where the website is stored.
The first thing to understand is that every web page has a domain name that is easy for humans to remember and type in (such as www.csnewbs.com) as well as a related IP address (such as 126.96.36.199) which is a unique address for the device that the web page is stored on.
The steps taken to display a web page:
A domain name is typed into the address bar of a browser.
The browser checks a local (cached) host file to check if it already holds the IP address, but if it doesn't...
A query is sent to the local DNS server for the corresponding IP address of the domain name.
The local DNS server will check if it holds an IP address corresponding to that domain name. If it does it passes the IP address to your browser.
The browser then connects to the IP address of the server and accesses the web site.
If the local DNS server does not hold the IP address then the query is passed to another DNS server at a higher level until the IP address is resolved.
If the IP address is found, the address is passed on to DNS servers lower in the hierarchy until it is passed to your local DNS server and then to your browser.
3.7 - The Internet:
1a. Describe the difference between the internet and the world wide web (WWW). 
1b. What is the purpose of a web browser? 
1c. Why do humans use URLs instead of IP addresses? 
1d. Write out the following URL and label each section:
2a. What is a DNS server? 
2b. Describe, using a mix of text and icons / images, how a DNS server is used to display a web page. 
2c. Describe how a DNS server searches for an IP address if it is not found on the local DNS server.