The Internet & World Wide Web (Leaving Cert Computer Science): Revision Notes

The Internet & World Wide Web

Network

Networks are classified by their size, scope and purpose. There are networks for personal areas, homes, businesses, cities etc.

The Internet

A web browser is an application that allows users to access, retrieve and view information on the World Wide Web. It acts as an interface between users and the Internet. When a user requests a web page from a particular website, the browser retrieves the files from a web server and renders the resource back to the user.

To access the resource, users typically input a URL into the browser, which stands for Uniform Resource Locator. This is a reference (address) to a resource on the Internet.

The process is known as the client-server model. Your computer acts as client and issues a request to access some resource. The server responds to the client by providing the requested service or resource.

Communication Protocols

Protocol are established to ensure consistent, reliable and standardised communication between devices regardless of hardware, software or their architecture.

Communication protocols are organised into layers each with specific functions. The OSI (Open Systems Interconnection) model is a conceptual framework that divides network communication into seven layers.

Requests travel down through each protocol layer in the client, through the Internet and then back up through the protocol layers in the server.

HTTP & HTTPS

Layer : Application

HTTP is request-response protocol :

1. The client sends a HTTP request to a server.
2. The web server receives the request, processes it and determines the appropriate response.
3. The server sends the HTTP response back to the client.
4. The client receives the responses and processes it. For web browsers, this typically means rendering the HTML to the client.

TCP

Layer : Transport

5. TCP first establishes a connection between the client and the server.
6. The data is broken up into packets for more efficient routing, each tracked by TCP using a sequence number.
7. After each packet has been transferred, the connection is terminated.

IP

Layer : Network

8. Data is encapsulated into IP packet consisting of a header and the payload. The header contains information for the routing including the source and destination IP address.
9. The IP packet is sent and routed until it reaches the destination.

TCP / IP Protocol Suite

The TCP / IP Protocol Suite is a set of communication protocols used to interconnect network devices over the Internet.

TCP keeps track of the packet information and ensures secure and reliable transmission while IP is responsible for the creation of the packets such as their addressing and routing.

The TCP / IP is composed of four layers, each responsible for a specific purpose.

• Application Layer : Responsible for encoding and decoding the data into a form that is understood by the client and server devices using protocols such as HTTPS.
• Transport Layer: Breaks down the data into packets where each packet is assigned a sequence number. The recipient uses this information to assemble the packets in the correct order and allows the recipient to identify missing packets.
• Network Layer: Handles the routing of data packets across network boundaries, providing logical addressing and packet forwarding. The network then knows where to send the message and where it came from.
• Data Link Layer: Enables the physical transfer of packets between nodes on a network or between one network to another.

Wi-Fi

VoIP

VoIP converts voice signals into digit data packets and transmits them over the network, enabling telephone calls, video calls and other forms of communication without relying on traditional telephone lines.

Network Hardware

Network hardware facilitates and manages data communication within a network.

Router

Function : Forwards data packets between computer networks. They provide and usually additional features such as firewall protection.

Gateway

Function : Connects networks using different protocols and facilitates communicate between them, for example, two different networks in an organisation.

Bridge

Function : Connects and philtres traffic between two or more network segments, creating a larger network.

Network Switch

Function : Forwards data packets only to devices that need to receive it.

Repeater

Function : Regenerates signals to extends the range of a network by re-transmitting the data.

Cloud Computing

Advantages of Cloud Computing

• Cost Efficiency
  • Users and organisations do not need to invest in expensive hardware and can instead pay for only what they use to cloud providers. Maintenance costs are also reduced as the cloud providers handle hardware and software upkeep.
• Disaster Recovery
  • Cloud provider offer comprehensive backup and recovery options, maintaining business continuity.
• Collaboration
  • Cloud providers support tools and platforms that enable multiple users to work on the same project simultaneously.

Disadvantages of Cloud Computing

• Security & Privacy
  • Storing sensitive data on the cloud can raise concerns about unauthorised access and data breaches.
• Data Transmission Costs
  • Transferring large volumes of data to and from the cloud can be expensive. Latency can affect performance, especially for real-time applications.
• Limited Control
  • Cloud users have less control over the underlying infrastructure compared to on-premise solutions.