Networks

A computer network connects devices so they can share data and resources. The type of network is defined by its geographical scale. A Local Area Network (LAN) covers a small area like a single office, building, or school campus. It's usually privately owned and managed. A Wireless Local Area Network (WLAN) is simply a LAN that uses wireless technology (like Wi-Fi) instead of physical cables. A Wide Area Network (WAN) connects LANs over a large geographical area, such as between cities or even countries. The most famous example of a WAN is the internet itself. WANs are often managed by multiple organisations and use public infrastructure like telephone lines or satellite links.

Beyond their scale, networks can be defined by who can access them. The Internet is a global, public network accessible by anyone with a connection. An Intranet is a private network belonging to a single organisation, like a company or a school. It uses the same technology as the internet (web pages, browsers) but is only accessible to people inside the organisation. It's used for internal communication, sharing documents, and posting company news. An Extranet is an extension of an intranet. It's a private network that allows controlled access to specific external users, such as business partners, suppliers, or customers. For example, a car manufacturer might give its suppliers access to an extranet to check stock levels.

Several hardware devices are essential for networks to function. A Network Interface Card (NIC) is a circuit board inside a computer that allows it to connect to a network. A Hub is a simple device that connects multiple computers; when it receives data, it broadcasts it to every connected device, which can be inefficient and cause data collisions. A Switch is a smarter version of a hub; it inspects data packets and forwards them only to the specific device they are intended for, improving efficiency and security. A Bridge is used to connect two separate LAN segments and make them act as a single network. A Router is a more sophisticated device that forwards data packets between different networks, for example, connecting your home LAN to the internet (a WAN). It directs traffic and finds the best path for data to travel.

Wireless communication allows devices to connect to a network without physical cables. The two most common technologies are Wi-Fi and Bluetooth. Wi-Fi is used to create a Wireless Local Area Network (WLAN). It connects devices to a network, and usually to the internet, via a wireless router or access point. It has a range of up to 100 metres and is designed for high-speed data transfer. Bluetooth is designed for short-range communication between two devices, creating a Personal Area Network (PAN). It's used to connect peripherals like headphones, keyboards, and mice to a computer or phone. Its range is typically around 10 metres, and it uses less power and has lower bandwidth than Wi-Fi.

Cloud computing means accessing computer services—like storage, software, and processing power—over the internet instead of having them on your local computer. The most common use is cloud storage (e.g., Google Drive, iCloud, Dropbox), which allows you to save your files on remote servers and access them from any internet-connected device.

Advantages include:

• Accessibility: Access your files from anywhere, on any device.
• Collaboration: Multiple users can work on the same document simultaneously.
• Backup and Recovery: Files are automatically backed up, protecting against data loss from device failure or theft.

Disadvantages include:

• Internet Dependency: You need a reliable internet connection to access your files.
• Security Risks: Your data is stored by a third-party company, which could be a target for hackers.
• Costs: While some storage is free, large amounts of storage can require a monthly subscription fee.

Authentication is the process of verifying that someone (or something) is who they claim to be before granting them access to a network or system. There are three main factors of authentication:

1. Something you know: This is the most common form, typically a password or a PIN. Strong passwords are long, complex (using upper/lower case letters, numbers, and symbols), and not easily guessable.
2. Something you have: This involves a physical object, such as a security token that generates a one-time code, your smartphone (for receiving a code via SMS), or a bank card.
3. Something you are: This is biometrics. It uses unique biological characteristics like a fingerprint, facial recognition, or an iris scan.

Using two or more of these methods together is called Multi-Factor Authentication (MFA), which provides much stronger security than a password alone.

Once a user is authenticated, the data itself needs protection, both when it's stored and when it's being transmitted across a network. Key technologies for this are encryption, firewalls, and anti-malware software.

• Encryption scrambles data into an unreadable format called ciphertext. Only someone with the correct 'key' can decrypt it back into readable plaintext. This is vital for protecting sensitive data like credit card numbers during online transactions.
• A Firewall acts as a barrier between a trusted internal network (like your home or school network) and an untrusted external network (the internet). It monitors incoming and outgoing traffic and blocks data packets that don't meet a defined set of security rules.
• Anti-malware software is designed to detect, prevent, and remove malicious software (malware) from your computer. This includes viruses, spyware, ransomware, and other threats that can steal data or damage your system.

Electronic conferencing allows people in different locations to hold meetings using network technology, saving time and travel costs. There are three main types:

1. Audio-conferencing: A telephone call with multiple participants. It is voice-only and requires the least technology - just a phone or a computer with a microphone and speakers.
2. Video-conferencing: Adds a live video feed to audio-conferencing, so participants can see each other. This requires a webcam and a faster internet connection to handle the video data.
3. Web-conferencing: The most feature-rich type. It includes audio and video, but also adds other collaborative tools like screen sharing (to show a presentation), a shared whiteboard, text chat, and file sharing. This is done using specialised software like Zoom, Microsoft Teams, or Google Meet.

While conferencing reduces travel, it has drawbacks like reliance on technology, potential for technical issues, and difficulties with time zone differences.