Networks: topologies, hardware and the client-server model

LAN and WAN

A LAN covers one site and the organisation owns the cabling; a WAN spans sites and uses third-party infrastructure. The ownership difference is what drives the cost and security differences.

Topologies

Bus: one backbone, cheap, but a break kills the whole network and collisions rise with traffic. Star: every node to a central switch — one failed cable affects one node, but the switch is a single point of failure. Mesh: many paths, extremely resilient, expensive to cable. Hybrid mixes them, which is what real buildings use.

Hardware, precisely

A hub broadcasts to every port; a switch learns MAC addresses and forwards only to the destination port — less traffic and harder to eavesdrop. A router connects different networks and forwards by IP address. A NIC holds the MAC address. A gateway joins networks that use different protocols.

Client-server and peer-to-peer

Client-server centralises data, backup, access control and updates, at the cost of a server and of failing all at once. Peer-to-peer needs no server and scales cheaply, but backup and security are each user's problem. Choose by asking who must control the data.

Wireless

Wi-Fi trades speed and security for mobility; interference, walls and shared bandwidth all cut real throughput. Bluetooth suits short-range, low-power pairing. Encryption (WPA) matters more on wireless precisely because the signal leaves the building.