Computer Networks

A computer network is two or more computing devices connected to exchange and share information such as files, printing, and internet access. Connections are made using copper wires, fiber optic cables, or wireless radio signals.

Each device on a network is called a node. To communicate, nodes follow agreed-upon rules called protocols. Protocols define how data is divided, addressed, and verified to arrive correctly.

Types by Scale

A LAN (Local Area Network) connects devices within a single building or office. A WAN (Wide Area Network) connects distant locations such as cities or countries. There are also MANs covering a specific city and PANs for devices near a user, such as Bluetooth connections.

Architecture and Protocols

Modern networks typically use a layered model. The TCP/IP model has layers including the link layer, internet layer (IP), transport layer (TCP or UDP), and application layer. The OSI model has seven layers and is commonly used for teaching and description.

IP addresses identify each device on a network. The DNS system converts website names into IP addresses. Routers determine the path data takes between different networks, while switches distribute data among devices on a local network.

Security

Because data travels many routes, it requires protection. Common methods include encryption such as TLS, firewalls that control incoming and outgoing traffic, and authentication systems for users. Common attacks include eavesdropping and denial-of-service attacks (DDoS).