What Are Computer Networks?

Computer networks are interconnected systems of computing devices that exchange data using shared communication protocols over physical or wireless transmission media. A network may span a single room, a campus, a metropolitan area, or the entire globe, and its components include end devices such as workstations, servers, and smartphones; intermediate devices such as routers, switches, and access points; and the physical or wireless links that connect them. Computer networking draws on electrical engineering, information theory, and computer science, and the discipline has produced the infrastructure on which essentially all modern digital communication depends.

The conceptual foundation for modern networks was established in the 1960s through ARPANET research funded by the US Department of Defense, which demonstrated that packet-switched networks could route messages around failures. The development of the TCP/IP protocol suite in the 1970s by Vinton Cerf and Robert Kahn provided a vendor-independent internetworking layer that allowed heterogeneous networks to be interconnected, a capability that became the technical basis for the internet. Bit rate, the number of bits transmitted per unit time, and delay, including propagation delay and queuing latency, are the two primary performance dimensions that constrain what applications a network can support.

Network Architectures and Topologies

Computer networks are categorized by their geographic scope and physical organization. Local area networks (LANs) connect devices within a limited area, such as an office building, and are typically implemented using Ethernet or Wi-Fi. Personal area networks (PANs) span the range of a single person and commonly use Bluetooth or Zigbee. Wide area networks (WANs) span cities, countries, or continents and rely on leased fiber circuits, microwave links, or satellite links. LAN interconnection through switches and routers forms the basic architectural unit of larger networks, and multiprocessor interconnection using high-bandwidth fabrics such as InfiniBand connects the processors inside computing clusters used for scientific workloads. The IEEE 802 LAN/MAN Standards Committee maintains the specifications for Ethernet (802.3), Wi-Fi (802.11), and many other LAN and PAN technologies.

Protocols and Standards

Network protocols define the rules governing how devices establish connections, exchange data, handle errors, and manage congestion. The TCP/IP stack organizes these rules into layers: the network layer (IP) handles addressing and routing; the transport layer (TCP, UDP) handles end-to-end delivery and flow control; and the application layer hosts protocols such as HTTP, DNS, and SMTP. The IEEE 802.11 family of standards, commonly known as Wi-Fi, specifies the physical layer and medium access control procedures for wireless LANs and has expanded from the original 2 Mbit/s specification to multi-gigabit rates with the 802.11ax (Wi-Fi 6) and 802.11be (Wi-Fi 7) revisions. Internetworking protocols such as BGP govern how autonomous systems on the internet exchange routing information, enabling the decentralized global routing infrastructure. The IETF's RFC series documents the core internet protocols, including TCP (RFC 793) and IP (RFC 791), which have been foundational since their publication.

Network Services and Security

Computer networks support a range of services including file storage and retrieval via file servers, name resolution via DNS, time synchronization via NTP, and web content delivery via HTTP servers. Ports, standardized 16-bit numbers assigned by the IANA, allow multiple services to operate on a single IP address. Firewalls inspect traffic at network boundaries and enforce access control policies by permitting or blocking packets based on addresses, ports, and protocol state. Intrusion detection systems analyze traffic patterns for evidence of cyber attacks, including distributed denial-of-service campaigns associated with cyber warfare and cyber terrorism. The IEEE Xplore publications on network dependability and security provide analytical frameworks for evaluating these protective mechanisms systematically.

Applications

Computer networks have applications in virtually every sector of modern society, including:

• Distributed computing, enabling clusters and cloud platforms to aggregate processing across many machines
• Web services and content delivery, supporting e-commerce, media streaming, and information services
• Enterprise collaboration, including video conferencing, email, and shared storage systems
• Industrial automation and control, connecting sensors, programmable logic controllers, and SCADA systems
• Scientific research, through high-speed research and education networks linking universities and laboratories