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The Internet is a planetary [[computer network]]. It is a "network of networks" consisting of millions of smaller networks connected together as an "inter-network", hence the name "Inter-net."

A [[computer]] connected to the Internet, called a [[host]], can access information from a vast array of other computers and [[server]]s, and can send information back to them. This information travels across the Internet in the form of individual [[data packet]]s, which may take any number of different routes to get from their source to their destination.

The complex communications infrastructure of the Internet consists of hardware components and a system of software protocols. 

==Internet Hardware Components==
The hardware components of the Internet include a wide range of electronic devices, linked together in various ways. Hardware devices such as [[switch]]es and [[router]]s serve as individual network [[node]]s, receiving and transmitting [[data packet]]s. The [[data packet]]s are relayed across the [[computer network]] from one [[node]] to the next.

The hardware devices are linked together by copper wires, fiber-optic cables, wireless connections, and other linkage technologies.

==Internet Software Protocols==
The software system of the Internet is a set of communications protocols called the [[Internet Protocol Suite]]. This set of Internet protocols is also called the TCP/IP model, after two important protocols within it, the [[Transmission Control Protocol]] (TCP) and the [[Internet Protocol]] (IP).

The TCP/IP model organizes the protocols into a system of layers. There are four software layers and one hardware layer, as follows, from top to bottom:
*the [[Application Layer]] is the layer of the software application running on a computer connected to the Internet, such as a [[web browser]]
*the [[Transport Layer]] allows different computers on the network to communicate within the same application, for example computers operating under the client-server model
*the [[Internet Layer]] enables computers to connect to one-another via the intermediate networks (this layer establishes internetworking and the Internet)
*the [[Link Layer]] is a software layer that provides connectivity between devices on the same local link, such as a [[Local Area Network]] (LAN) or a dial-up connection. 
*the Hardware Layer consists of the physical devices making up the network

The [[Transmission Control Protocol]] (TCP) is a Transport Layer protocol, providing an intermediate service between an application program and the [[Internet Protocol]] (IP). When an application program desires to send a large chunk of data across the Internet, it can issue a single request to TCP and let TCP handle the details of breaking the data into IP-sized pieces and issuing a series of IP requests. 

TCP is a rather complex protocol that ensures reliable, connection-oriented transmissions. An alternative Transport Layer protocol, the connectionless [[User Datagram Protocol]] (UDP), can be used for simpler messaging transmissions. 

The central component of the Internet model is the [[Internet Protocol]] (IP), which occupies the Internet Layer. It has the task of delivering [[data packet]]s from the source [[host]] to the destination host. For this purpose, the Internet Protocol defines methods for encapsulating data from an upper layer protocol into packets, and addressing systems so that the packets can reach their destination. For outgoing packets, the Internet Protocol selects the nearest intermediate Host and transmits the packet to it using appropriate Link Layer drivers. For incoming packets, IP captures the packets and passes their payload up to the appropriate Transport Layer module.

==Internet Applications==
The Internet is used for a wide variety of applications. Some of these, such as [[email]], were used on computer networks prior to the appearance of the Internet, while others, such as the [[Web]], only developed because the Internet made them possible.

Some of the most widely-used types of Internet applications are:
*[[Email]]
*[[File transfer]] such as with [[File Transfer Protocol]] (FTP)
*[[Remote access]] to other computers, such as with [[Secure Shell]]
*[[Web|World Wide Web]], for viewing [[website]]s with a [[web browser]], or for creating [[blog]]s or [[website]]s
*[[Online chat]]
*[[Online game]]s
*[[Collaborative software]], such as [[wiki]]s
*[[Social media]]
*[[Streaming media]]
*Internet Telephony ([[VoIP]])

==Internet Access==
[To be written]

==Internet Organizations==
[To be written]

==See Also==
*[[History of the Internet]]
*[[Cyberculture]]

[[Category:Internet protocols]]