Client-Server and Peer-to-Peer Models

At A-Level you must understand the two fundamental network models — client-server and peer-to-peer (P2P) — and be able to compare them in terms of architecture, management, security, scalability and use-cases.

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Client-Server Model

In the client-server model, a central server provides services or resources, and clients request those services. The server is a dedicated, powerful machine that is always running; clients are the end-user devices.

    ┌────────┐
    │ Client │──────┐
    └────────┘      │
    ┌────────┐      │     ┌────────┐
    │ Client │──────┼────→│ Server │
    └────────┘      │     └────────┘
    ┌────────┐      │
    │ Client │──────┘
    └────────┘

Roles

Component	Role
Server	Stores and manages shared resources (files, databases, applications); authenticates users; enforces security policies
Client	Requests services from the server; presents data to the user

Examples

• Web: A browser (client) requests pages from a web server.
• Email: An email client connects to a mail server (SMTP/IMAP/POP3).
• File server: Users save and retrieve files from a central file server.
• Database server: Applications query a central database.

Advantages