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A computer network is an
interconnection of a group of computers. Networks may be
classified by what is called the network layer at which they
operate according to basic reference models considered as
standards in the industry such as the four-layer Internet
Protocol Suite model. While the seven-layer Open Systems
Interconnection (OSI) reference model is better known in
academia, the majority of networks use the Internet Protocol
Suite (IP) as their network model.
Basic Hardware Components
All networks are made up of basic hardware building blocks
to interconnect network nodes, such as Network Interface
Cards (NICs), Bridges, Hubs, Switches, and Routers. In
addition, some method of connecting these building blocks is
required, usually in the form of galvanic cable (most
commonly Category 5 cable). Less common are microwave links
(as in IEEE 802.11) or optical cable.
Network Interface Cards
A network card, network adapter or NIC (network
interface card) is a piece of computer hardware designed to
allow computers to communicate over a computer network. It
provides physical access to a networking medium and often
provides a low-level addressing system through the use of
MAC addresses. It allows users to connect.
Switches
Switches are a marketing term that encompasses routers and
bridges, as well as devices that may distribute traffic on
load or by application content. Switches may operate at one
or more OSI layers, including physical, data link, network,
or transport (i.e., end-to-end). A device that operates
simultaneously at more than one of these layers is called a
multilayer switch.
Overemphasizing the ill-defined term "switch" often leads to
confusion when first trying to understand networking. Many
experienced network designers and operators recommend
starting with the logic of devices dealing with only one
protocol level, not all of which are covered by OSI.
Multilayer device selection is an advanced topic that may
lead to selecting particular implementations, but multilayer
switching is simply not a real-world design concept.
Routers
Routers are the networking device that forward data packets
along networks by using headers and forwarding tables to
determine the best path to forward the packets. Routers work
at the network layer of the TCP/IP model or layer 3 of the
OSI model. Routers also provide interconnectivity between
like and unlike media (RFC 1812) This is accomplished by
examining the Header of a data packet, and making a decision
on the next hop to which it should be sent (RFC 1812) They
use preconfigured static routes, status of their hardware
interfaces, and routing protocols to select the best route
between any two subnets. A router is connected to at least
two networks, commonly two LANs or WANs or a LAN and its
ISP's network. Some DSL and cable modems, for home use, have
been integrated with routers to allow multiple home
computers to access the Internet.
Practical networks generally consist of more than two
interconnected computers and generally require special
devices in addition to the Network Interface Controller that
each computer needs to be equipped with. Examples of some of
these special devices are hubs, switches and routers.
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