Summary — What This Chapter Covers
- Networks let users share files, printers and internet access, communicate, and manage security and backups centrally.
- A LAN covers a small area with infrastructure the owner controls; a WAN covers a large area and uses third-party communication links.
- Client-server centralises resources and control; peer-to-peer treats every computer equally. Thin clients depend on a server; thick clients can work on their own.
- Bus, star, mesh and hybrid topologies, how packets travel in each, and which to choose.
- Cloud computing (public and private), wired versus wireless, and the properties of copper, fibre, radio, microwave and satellite links.
- LAN hardware (switch, server, NIC, WNIC, WAP, cables, bridge, repeater), routers, Ethernet and CSMA/CD.
- Bit streaming (real-time and on-demand) and why bit rate matters.
- The internet is the hardware network; the WWW is a service on it. IPv4/IPv6, subnetting, public/private and static/dynamic addresses, URLs and DNS.
1. Networks, LANs and WANs
Networks including the internet
Why connect computers at all
Benefits of networking: share files and data; share hardware (printers, storage) and one internet connection; communicate by email and messaging; install software and updates centrally; manage user accounts, security and backups from one place.
| LAN (local area network) | WAN (wide area network) |
|---|
| Area | One building or site | Large geographical area: a city, country or the world |
| Links | Owned and managed by the organisation | Leased or third-party links (telephone lines, fibre, satellite) |
| Speed / errors | Higher bandwidth, fewer errors | Usually lower bandwidth, more chance of errors |
| Example | A school network | The internet; a bank linking its branches |
Practice Question
State two benefits to a school of connecting its 200 computers as a LAN.
2. Network Models: Client-server, Peer-to-peer, Thin and Thick Clients
Networks including the internet
Who provides and who requests
In the client-server model, one or more servers provide a service (file storage, printing, email, web pages, authentication) and clients request it. Resources, security and backups are centralised, so it suits larger networks, but the server is a single point of failure and costs more to buy and manage. A network can be split into subnetworks (for example one per department), each with its own servers, to reduce traffic and improve security.
In a peer-to-peer network every computer has equal status: each can share its own files and act as both client and server. It is cheap and simple for a few computers and has no single point of failure, but there is no central backup or security, and a file is unavailable when the peer holding it is switched off. File-sharing applications and small home networks use it.
thin client
thick client
| Thin client | Thick client |
|---|
| Processing | On the server | On the client |
| Needs connection | All the time | Only to exchange data |
| Client hardware | Cheap, low specification | More powerful, more expensive |
| Security / updates |