GCSE Computer Science - Topic 4 Networks

What is the difference between a LAN and a WAN?

LAN (Local Area Network) covers a small site like a building; WAN (Wide Area Network) connects LANs over a large geographical area using leased lines or satellites.

Define Bandwidth and Latency.

Bandwidth is the volume of data that can be sent in a given time (bps); Latency is the time delay for data to travel from source to destination.

List 3 factors that affect network performance.

1. Bandwidth, 2. Number of users (contention), 3. Transmission media (e.g. copper vs fibre).

How are network speeds measured?

Measured in bits per second (bps): Kilobits (1,000), Megabits (1,000,000), and Gigabits (1,000,000,000).

What is the formula for network transmission time?

Time (seconds) = File size (bits) / Transmission rate (bps).

What is a Protocol?

A set of rules that govern how devices communicate and how data is transmitted across a network.

What are the roles of IP addresses and Routers?

IP addresses uniquely identify a device's location on a network; Routers use these addresses to direct data packets to their destination.

Describe Ethernet and Wi-Fi.

Ethernet is a protocol for wired LANs; Wi-Fi is a family of protocols for wireless data transmission using radio waves.

What are TCP and IP responsible for?

TCP (Transmission Control Protocol) handles packet sequencing and error checking; IP (Internet Protocol) handles the routing of packets.

What are HTTP and HTTPS used for?

Used by web browsers to access websites; HTTPS is the secure, encrypted version.

What is FTP used for?

File Transfer Protocol is used for the transmission of files across a network.

What are the three email protocols (POP3, SMTP, IMAP)?

SMTP sends emails; POP3 downloads and deletes them from the server; IMAP syncs emails across devices.

Name the 4 layers of the TCP/IP model.

1. Application, 2. Transport, 3. Internet, 4. Link.

What happens at the Application and Transport layers?

Application provides services to apps (HTTP/FTP); Transport handles packet switching and error checking (TCP).

What happens at the Internet and Link layers?

Internet handles routing and IP addressing; Link handles the physical transmission of data via hardware/drivers.

Describe a Star Topology.

All devices connect to a central switch. If one cable fails, only that device is affected. High performance but expensive.

Describe a Mesh Topology.

Devices are interconnected. Very reliable as there is no single point of failure, but complex to set up.

Describe a Bus Topology.

All devices share a single backbone cable. Cheap to install but slow if many users are on it; if the backbone fails, the whole network goes down.

What is the difference between the Internet and the WWW?

The Internet is the physical infrastructure (cables/routers); the WWW is a collection of web pages accessed via the internet.

What is the role of the DNS?

Translates human-readable domain names (e.g. https://www.google.com/search?q=google.com) into IP addresses that computers can understand.

What is Penetration Testing?

Simulating a cyber attack on a network to identify and fix security vulnerabilities.

What is the difference between Ethical Hacking and a real attack?

Ethical hacking is legal, authorized testing to find flaws; a real attack is unauthorized and malicious.

What is Access Control?

Security that restricts user permissions, ensuring people can only access the data and files they are authorized to see.

Give examples of Physical Security.

Locking server rooms, using CCTV, security guards, or biometric scanners for building entry.

How do Firewalls protect a network?

They monitor incoming and outgoing traffic and block unauthorized access based on a set of security rules.