The Internet (OCR GCSE Computer Science): Revision Notes

The Internet

• The Internet is a global network of interconnected computer networks.
• It is the largest Wide Area Network (WAN), connecting millions of devices worldwide, allowing them to communicate and share data.

World Wide Web (WWW)

• The World Wide Web (WWW) is a collection of websites and resources that are accessed through the Internet.
• The Internet and WWW are not the same; the WWW is one of many services available on the Internet, alongside email, file sharing, and more.

Domain Name System (DNS)

• Every website has a unique IP address that computers use to locate it, but these can be difficult to remember.
• A Domain Name System (DNS) translates easy-to-remember domain names (e.g., www.google.com) into their corresponding IP addresses.

How DNS works

• When you enter a URL, the DNS server looks up the domain name to find the associated IP address.
• If the DNS server doesn't know the address, it will ask other DNS servers.
• Once the IP address is found, your browser can connect to the website.

Benefits of DNS

• Simplifies navigation: Users don't need to remember complex IP addresses.
• Distributed system: DNS servers are spread globally, and they constantly update each other.
• Efficiency: If a DNS server doesn't have the IP address, it can find it from another DNS server, ensuring websites are always accessible.

Hosting

• Hosting refers to storing files or resources (such as websites) on a remote server so they can be accessed over the Internet.
• Websites are hosted on web servers. When you visit a website, your browser connects to the server hosting that site to retrieve its files.
• Example: A company might host their website on a web server, allowing users to access it from anywhere by typing in the domain name.

Web Servers and Clients

• A web server stores and delivers web pages to users when requested.
• The client (such as a web browser) sends requests to the server (e.g., asking for a web page) and receives the information to display on the user's device.
• Example: When you type in a URL, your browser (client) requests the web page from the server that hosts it.

The Cloud

• The Cloud allows people to store data and run applications on remote servers, which are accessed via the Internet.
• Cloud services include storage (e.g., Google Drive, Dropbox), software (e.g., Google Docs), and processing (e.g., cloud gaming).

Advantages of the Cloud

• Flexible storage: You can increase your storage capacity as needed.
• Remote access: Files and applications can be accessed from anywhere with an internet connection.
• Cost-effective: No need to invest in expensive hardware or IT staff.
• Automatic backups: Cloud providers manage security and backups, ensuring data protection.

Disadvantages of the Cloud

• Internet dependency: Requires a stable internet connection to access files.
• Security concerns: Trusting third parties with sensitive data can make it vulnerable to hacking.
• Ongoing costs: Some cloud services require expensive subscription fees.
• Data ownership: There can be concerns over who legally owns the data stored in the cloud.

Virtual Networks

• A Virtual Network is a software-based network that exists within a physical network.
• Multiple virtual networks can exist on the same physical infrastructure without the need for additional hardware.
• Each virtual network can have its own security measures and firewalls.
• Example: A school might have a virtual network for students and a separate one for staff, both running on the same physical network but kept isolated for security.