A **computer network** is a collection of [[Computer|computers]] and other [[Computer hardware|hardware]] devices interconnected by [[Telecommunications equipment|communication channels]] that allow sharing of resources and information. Networks may be classified by their scale, ranging from [[Personal area network|personal area networks]] and [[Local area network|local area networks]] to [[Wide area network|wide area networks]] and the global [[Internet]]. Devices on a network communicate using [[Communication protocol|network protocols]], with the [[Internet protocol suite]] ([[TCP/IP]]) serving as the foundational protocol stack for most modern networks. The development of computer networks began in the late 1960s with [[ARPANET]], a project funded by the [[United States Department of Defense]] that pioneered [[Packet switching|packet-switching]] technology. This work laid the groundwork for the modern Internet and influenced the development of key technologies including [[Ethernet]], developed by [[Robert Metcalfe]] at [[Xerox PARC]] in the 1970s, and the [[World Wide Web]], created by [[Tim Berners-Lee]] at [[CERN]] in 1989. The [[OSI model]] and the TCP/IP model provide conceptual frameworks for understanding how data moves through layered [[Network architecture|network architectures]]. Computer networks are fundamental to modern [[Telecommunication|telecommunications]], [[Cloud computing|cloud computing]], and [[Distributed computing|distributed systems]]. Networks can be organized using various [[Network topology|topologies]]—such as [[Star network|star]], [[Mesh networking|mesh]], and [[Bus network|bus]]—and may use wired media such as [[Optical fiber|fiber optics]] and [[Ethernet over twisted pair|twisted-pair cable]] or [[Wireless network|wireless]] technologies including [[Wi-Fi]] and [[Cellular network|cellular networks]]. [[Network security]] remains a critical concern, encompassing measures such as [[Firewall (computing)|firewalls]], [[Encryption|encryption]], and [[Intrusion detection system|intrusion detection systems]] to protect data integrity and privacy.