What is the fundamental difference between a LAN and a WAN regarding infrastructure ownership?

In a LAN, the organization or individual typically owns all the hardware and cabling. In a WAN, the infrastructure is usually provided by third-party telecommunication companies and is leased by the users.

How does the Client-Server model differ from the Peer-to-Peer model in terms of resource management?

The Client-Server model uses a central server to manage and host all resources, providing them to clients upon request. In a Peer-to-Peer model, resources are distributed across all machines, and every machine has equal responsibility for sharing data.

What is the difference between a Thin Client and a Thick Client regarding network dependency?

A Thin Client requires a permanent, stable network connection to a server to function because it lacks local processing power. A Thick Client can function independently and run applications offline because it uses its own internal hardware for processing.

What is a common misconception about the security of Peer-to-Peer networks?

Many assume P2P is secure because there is no central server to attack, but in reality, security is often weaker because it relies on individual users to manage their own backups, antivirus, and access rights, leading to inconsistencies.

Why is it incorrect to say that a WAN is simply a 'large LAN'?

A WAN is not just a larger version of a LAN; it is a collection of interconnected LANs. It uses different technologies, such as routers and public communication links, and operates over a much larger geographical scale with different ownership structures.

What error occurs when a network designer ignores the 'single point of failure' in a Client-Server setup?

If the central server fails, the entire network becomes unusable for all clients. Designers must implement redundancy or failover systems to mitigate the risk of a total network shutdown.

Define a Local Area Network (LAN).

A LAN is a group of interconnected computers and devices confined to a small geographic area, such as a home or office, used for sharing resources like printers and files.

What is a Wireless Access Point (WAP)?

A WAP is a hardware device that allows wireless-capable devices to connect to a wired network using Wi-Fi standards, effectively creating a WLAN.

What is the role of a Router in a WAN?

A router acts as a gateway that connects different networks together. It analyzes data packets to determine the most efficient path for data to travel from one LAN to another across the WAN.

Why are software licenses often cheaper in a networked environment?

Network versions of software allow for site licenses or concurrent user licenses, which are typically more cost-effective than purchasing individual standalone licenses for every single computer.

Revision Notes

AS-Level

Cambridge International Examinations

Computer Science

2. Communication

Network types

Network Types and Architectures

Summary

Computer networks are classified based on their geographical scale, the logical relationship between connected devices, and the distribution of processing power. Understanding these classifications—ranging from Local and Wide Area Networks to Client-Server and Peer-to-Peer models—is essential for designing efficient, secure, and scalable communication systems.

1. Geographical Classification: LAN vs. WAN

Local Area Network (LAN): A network that spans a small, restricted geographical area, typically within a single building or campus. The infrastructure is usually owned and maintained by the organization using it, utilizing high-speed connections like Ethernet or Wi-Fi.
Wide Area Network (WAN): A network that connects multiple smaller networks across large distances, such as cities, countries, or continents. WANs often rely on third-party telecommunication infrastructures, including leased lines, satellites, and fiber-optic cables, to facilitate long-distance data transfer.
Wireless Local Area Network (WLAN): A subset of LANs that uses radio waves instead of physical cabling to connect devices. While offering high portability and ease of installation, WLANs are more susceptible to interference and security vulnerabilities compared to wired counterparts.

Diagram showing a Wide Area Network (WAN) connecting three distinct Local Area Networks (LANs) via routers and long-distance communication lines.

2. Network Models: Client-Server vs. Peer-to-Peer

Client-Server Model: A hierarchical architecture where powerful central computers (servers) provide resources and services to less powerful workstations (clients). This model allows for centralized management of security, backups, and software updates, but creates a single point of failure if the server goes down.
Peer-to-Peer (P2P) Model: A decentralized architecture where every device has equal status and can act as both a client and a server. P2P networks are easier and cheaper to set up for small groups, as they require no specialized server hardware, but they become difficult to manage and secure as the number of users increases.

3. Processing Distribution: Thin vs. Thick Clients

Thin Client: A device or software that relies heavily on a central server for processing power and data storage. It requires a constant, high-quality network connection to function, as most applications run on the server side rather than the local hardware.
Thick Client: A workstation that performs the bulk of its processing locally and can function independently of a network connection. While more expensive due to higher hardware requirements, thick clients offer better performance for resource-intensive tasks and can work offline.

4. Key Distinctions

5. Exam Strategy & Tips