📘 01-01: What Is a Network?¶
📌 Definition¶
A computer network is a collection of two or more interconnected devices that communicate and share resources over a shared medium.
- Devices (nodes/hosts): computers, phones, printers, servers, routers
- Medium: wired (copper, fiber) or wireless (Wi-Fi, cellular)
- Resources shared: files, printers, Internet access, applications
💡 Why Networks Exist¶
- Share hardware (printers, storage)
- Share data and applications
- Enable communication (email, voice, video)
- Centralize management and security
📌 Peer-to-Peer vs. Client-Server¶
Networks are organized in one of two logical models.
| Feature | Peer-to-Peer (P2P) | Client-Server |
|---|---|---|
| Control | Decentralized — each host manages itself | Centralized on servers |
| Security | Per-device, hard to manage | Centralized (accounts, policies) |
| Cost | Low, minimal setup | Higher (server + NOS) |
| Scalability | Poor (a few devices) | Excellent (hundreds+) |
| Example | Two PCs sharing a folder | Corporate domain with a file server |
- A Network Operating System (NOS) (e.g., Windows Server, Linux server) controls access in the client-server model.
- Client-server centralizes authentication, backups, and resource control — the norm for organizations.
📌 Network Sizes (Scope)¶
| Type | Scope | Example |
|---|---|---|
| PAN | Around one person | Bluetooth headset |
| LAN | Building / campus | Office network |
| MAN | City / metro area | City-wide fiber ring |
| WAN | Large geographic area | The Internet, multi-site company |
Tip
Key idea — A network is about sharing resources reliably. The organizational model (peer-to-peer vs. client-server) determines how control and security are managed, while the scope (PAN/LAN/MAN/WAN) describes how far it reaches.
See also: Network Models & Topologies, The OSI Model