A computer network is an interconnection of a group of computers. The Internet is also a network - specifically a wide-area network. Networks may be classified by what is called the network layer at which they operate, according to basic standards in the industry such as the four-layer Internet Protocol Suite (IP) model. While the seven-layer Open Systems Interconnection (OSI) reference model is better known in academia, the majority of networks use the Internet Protocol (TCP/IP) as their network model.
Computer networks are also classified according to the scale: Personal Area Network (PAN), Local Area Network (LAN), Campus Area Network (CAN), Metropolitan area network (MAN), or Wide area network (WAN). As Ethernet increasingly is the standard interface to networks, these distinctions are more important to the network administrators than the end user. Network administrators may have to tune the network (and network hardware), based on distance delays, to achieve the desired Quality of Service (QoS). The primary difference in the networks is the size.
An intranet is a set of interconnected networks, using the Internet Protocol and uses IP-based tools such as web browsers, that is under the control of a single entity that closes the intranet to the rest of the world, and allows only specific users. Most commonly, an intranet is the internal network of a company or other enterprise, that typically relies on Cat5 cables or an internal wireless router, with network attached storage and print servers. For many the easiest way to begin is to buy a Network Starter Kit.
An extranet is a network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities (e.g. a company's customers may be given access to some part of its intranet creating in this way an extranet, while at the same time the customers may not be considered 'trusted' from a security standpoint). Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although, by definition, an extranet cannot consist of a single LAN; it must have at least one connection with an external network.
The Internet, of course, is a specific internetwork, consisting of a worldwide interconnection of governmental, academic, public, and private networks based upon the Advanced Research Projects Agency Network (ARPANET) developed by ARPA of the U.S. Department of Defense - also home to the World Wide Web (WWW) and referred to as the 'Internet' with a capital 'I' to distinguish it from other generic internetworks. Participants in the Internet, or their service providers, use IP Addresses obtained from address registries that control assignments. Service providers and large enterprises also exchange information on the reachability of their address ranges through the BGP Border Gateway Protocol.
However, the Network Hardware components that help connect computers together, plays a huge role in the performance of networks. It is important to choose Computer networking hardware devices based upon the desired performance, and configuration of the network to engineer the results needed. Computer network hardware, such as Routers, Managed and Unmanaged Switches, Hubs, Firewalls, and Gateways should be selected and tuned for maximum performance.
Some of the leading manufacturers of computer network hardware include: 3COM, ATEN Technology, Belkin, Buffalo Technologies, Cables To Go, Cisco, D-Link, Hewlett Packard, Intel, Linksys, NetGear, logear, WatchGuard, Trendnet, and others.