Chapter 2 Final Revision #1

Any device connected to a network, such as a computer, storage device, or peripheral (e.g., a printer).

PAN: Centered around a person or workspace to connect personal devices. WPAN: A wireless local network connecting devices in very close proximity, such as a laptop, smartphone, and printer.

LAN: Covers a small geographical area like a single building. The infrastructure is privately owned and not controlled by external organisations. WLAN: A wireless version of a LAN that uses radio waves for communication instead of physical cables.

MAN: Covers several buildings in a city, larger than a LAN but smaller than a WAN. WAN: Covers a very large geographical area, potentially connecting computers thousands of kilometres apart.

A WAN is composed of many LANs connected together through a Public Switched Telephone Network (PSTN) or satellites. WANs can connect computers that are thousands of kilometers apart. Often utilises fibre-optic cables and switch-to-switch transmission.

• WAN covers a large geographical area, whereas a LAN covers a small geographical area. • LAN connections between devices are usually physical, whereas WAN connections are often virtual. • A LAN has a high data transfer rate, whereas a WAN has a low data transfer rate. • The ownership of a LAN is private; the ownership of a WAN can be private or public. • A LAN is usually more secure than a WAN because protection is easier to implement.

Hardware: (Wireless) routers, Switches, Cables. Software: Firewalls, Operation and manegment of the network (sending and reviving data packets).

• Allows central management of the network (e.g., centralised backup and security). • Sharing peripheral devices and other hardware/software resources. • Software licenses for networks are cheaper. • Users can share data/files easily and communicate between devices.

• High initial cost for setup. • Complex manegment. • Security threats from malware and hacking, as if one device is hacked, the entire network is compromised.

A network model where computers that serve, provide resources or services are servers and computers that request those resources/services are clients. Tasks are split between the two: the server performs all processes required by the task and/or data storage, while clients only send requests to the server and display the returned results.

Web pages/files are saved on servers. Clients send requests to the web servers (for the files/pages). Web servers process the requests and return the results to the client, and the client (computer) displays the results to the user.

• All computers are of equal status. • Each computer provides access to resources and data. • Computers can communicate and share resources. • Each computer is responsible for its own security.

• Peer: Any computer connected to the network. • Swarm: All peers sharing or downloading parts of the same file. • Seed: A peer with 100% of the file. • Leech: A peer with an incomplete file currently downloading from others. • Tracker: Central server storing details and IP addresses of the swarm allowing them to connect. • Torrent File: Created by original peer, cotains metadata (acts as a map to the clients with a specific file).

• Torrent file is made avalible for download. • File to be shared is split into pieces. • BitTorrent client software is made avalible for other peers, allowing them to work as seeds or leeches • A peer can act as a seed when uploading parts of a file. • When a peer is downloading a file it can get parts of the file from different seeds simultaneously. • That peer then becomes a seed for the downloaded parts. • Tracker keeps records of all the peers and the parts of the file they have.

• Distributes the file data across multiple users, reducing the load on a single server. • Downloads from multiple sources simultaneously, speeding up the process of downloading a file. • If one source goes offline, others can still provide the file.

• Reduced security, so the network is only as secure as the weakest computer on the network, and each computer is at risk from viruses from other computers • No central management of backup, if the data from one computer is not backed up it is lost to all of them • No central management of files/software so consistency may be difficult to maintain as each computer may have different software from the others • Individual computers may respond slower because they are being accessed by other computers • To share files all the computers involved need to be switched on so the files may not be always available

Thin Client: Dependent on a server for processing; the server performs all/most processing for the client; most features fail without a connection. Thick Client: Functions like a standard computer; the server performs minimal/some processing for the client, while clients do most of their own processing/work independently (most resources are installed locally) and can operate offline.

Pros: Cheaper to expand; automatic central updates; centralised security. Cons: High reliance on server/network link; high initial server startup costs.

Pros: Robust and works offline; more user control over data. Cons: Less secure (individual responsibility); requires manual software updates per client.

Bus: Uses a single central cable (backbone); requires terminators to prevent signal reflection. Star: All devices connect to a central hub or switch which directs data packets.

Bus: Damage to the main cable would result in entire network failure, not secure (sends data to all computers) Star: High initial installation costs, central hub faliure afects the entire network.