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Building a computer network
A simple network
A simple computer network may be constructed from two computers by adding a
network adapter (Network Interface Controller (NIC)) to each computer and then
connecting them together with a special cable called a crossover cable. This
type of network is useful for transferring information between two computers
that are not normally connected to each other by a permanent network connection
or for basic home networking applications. Alternatively, a network between two
computers can be established without dedicated extra hardware by using a
standard connection such as the RS-232 serial port on both computers, connecting
them to each other via a special crosslinked null modem cable.
Practical networks
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 listed above under Basic Computer Network Building
Blocks / Other devices.
Types of networks:
Below is a list of the most common types of computer networks.
A personal area network (PAN) :
A personal area network (PAN) is a computer network used for communication among
computer devices (including telephones and personal digital assistants) close to
one person. The devices may or may not belong to the person in question. The
reach of a PAN is typically a few meters. PANs can be used for communication
among the personal devices themselves (intrapersonal communication), or for
connecting to a higher level network and the Internet (an uplink).
Personal area networks may be wired with computer buses such as USB and
FireWire. A wireless personal area network (WPAN) can also be made possible with
network technologies such as IrDA and Bluetooth.
Local Area Network (LAN):
A network that is limited to a relatively small spatial area such as a room, a
single building, a ship, or an aircraft. Local area networks are sometimes
called a single location network.
Note: For administrative purposes, large LANs are generally divided into smaller
logical segments called workgroups. A workgroup is a group of computers that
share a common set of resources within a LAN.
Campus Area Network (CAN):
A network that connects two or more LANs but that is limited to a specific
(possibly private) geographical area such as a college campus, industrial
complex, or a military base
Note: A CAN is generally limited to an area that is smaller than a Metropolitan
Area Network.
Metropolitan Area Network (MAN):
A network that connects two or more Local Area Networks or CANs together but
does not extend beyond the boundaries of the immediate town, city, or
metropolitan area. Multiple routers, switches & hubs are connected to create a
MAN
Wide Area Networks (WAN):
A WAN is a data communications network that covers a relatively broad geographic
area and that often uses transmission facilities provided by common carriers,
such as telephone companies. WAN technologies generally function at the lower
three layers of the OSI reference model: the physical layer, the data link
layer, and the network layer.
Types of WANs:
Centralized:
A centralized WAN consists of a central computer that is connected to dumb
terminals and / or other types of terminal devices.
Distributed:
A distributed WAN consists of two or more computers in different locations and
may also include connections to dumb terminals and other types of terminal
devices.
Internetwork:
Two or more networks or network segments connected using devices that operate at
layer 3 (the 'network' layer) of the OSI Basic Reference Model, such as a
router.
Note: Any interconnection among or between public, private, commercial,
industrial, or governmental networks may also be defined as an internetwork.
Internet, The:
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.
Intranet:
A network or internetwork that is limited in scope to a single organization or
entity or, also, a network or internetwork that is limited in scope to a single
organization or entity and which uses the TCP/IP protocol suite, HTTP, FTP, and
other network protocols and software commonly used on the Internet.
Note: Intranets may also be categorized as a LAN, CAN, MAN, WAN, or other type
of network.
Extranet:
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 provided access to some part of its intranet thusly
creating an extranet while at the same time the customers may not be considered
'trusted' from a security standpoint).
Note: 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, because an extranet must have at least one connection with an
outside network.
Intranets and extranets may or may not have connections to the Internet. If
connected to the Internet, the intranet or extranet is normally protected from
being accessed from the Internet without proper authorization. The Internet
itself is not considered to be a part of the intranet or extranet, although the
Internet may serve as a portal for access to portions of an extranet.
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