|
Computer Networking (also see
Computer
Networks) is the engineering discipline concerned
with communication between computer systems or
devices. Networking, routers, routing protocols,
and networking over the public Internet have their
specifications defined in documents called RFCs.
Communicating computer systems constitute
a computer network and these networks generally
involve at least two devices capable of being
networked with at least one usually being a computer.
The devices can be separated by a few meters (e.g.
via Bluetooth) or nearly unlimited distances (e.g.
via the Internet). Computer networking is sometimes
considered a sub-discipline of telecommunications,
and sometimes of computer science, information
technology and computer engineering. Computer
networks rely heavily upon the theoretical and
practical application of these scientific and
engineering disciplines.
A computer network is any set of computers
or devices connected to each other. Examples of
networks are the Internet, or a small home local
area network (LAN) with two computers connected
with standard networking cables connecting to
a network interface card in each computer. All
modern aspects of the Public Switched Telephone
Network (PSTN) are computer-controlled, and telephony
increasingly runs over the Internet Protocol,
although not necessarily the public Internet.
Views of networks
Users and network administrators often have different
views of their networks. Often, users that share
printers and some servers form a workgroup, which
usually means they are in the same geographic
location and are on the same LAN. A community
of interest has less of a connotation of being
in a local area, and should be thought of as a
set of arbitrarily located users who share a set
of servers, and possibly also communicate via
peer-to-peer technologies.
Network administrators see networks
from both physical and logical perspectives. The
physical perspective involves geographic locations,
physical cabling, and the network elements (e.g.,
routers, bridges and application layer gateways
that interconnect the physical media. Logical
networks, called, in the TCP/IP architecture,
subnets , map onto one or more physical media.
For example, a common practice in a campus of
buildings is to make a set of LAN cables in each
building appear to be a common subnet, using virtual
LAN (VLAN) technology.
Both users and administrators will
be aware, to varying extents, of the trust and
scope characteristics of a network. Again using
TCP/IP architectural terminology, an intranet
is a community of interest under common administration,
usually in the same enterprise. An extranet creates
a community of interest that spans multiple enterprises
and usually involves multiple administrators,
but is not accessible by arbitrary users of the
public Internet.
Informally, the Internet is the set
of users, enterprises,and content providers that
are interconnected by Internet Service Providers
(ISP). From an engineering standpoint, the Internet
is the set of subnets, and aggregates of subnets,
which share the registered IP address space and
exchange information about the reachability of
those IP addresses using the Border Gateway Protocol.
Typically, the human-readable names of servers
are translated to IP addresses, transparently
to users, via the directory function of the Domain
Name System (DNS).
Over the Internet, there can be business-to-business
(B2B), business-to-consumer (B2C) and consumer-to-consumer
(C2C) communications. Especially when money or
sensitive information is exchanged, the communications
are apt to be secured by some form of communications
security mechanism. Intranets and extranets can
be securely superimposed onto the Internet, without
any access by general Internet users, using secure
Virtual Private Network (VPN) technology.
History
Before the advent of computer networks that were
based upon some type of telecommunications system,
communication between calculation machines and
early computers was performed by human users by
carrying instructions between them. Many of the
social behavior seen in today's Internet was demonstrably
present in nineteenth-century telegraph networks,
and arguably in even earlier networks using visual
signals.
In September 1940 George Stibitz used
a teletype machine to send instructions for a
problem set from his Model K at Dartmouth College
in New Hampshire to his Complex Number Calculator
in New York and received results back by the same
means. Linking output systems like teletypes to
computers was an interest at the Advanced Research
Projects Agency (ARPA) when, in 1962, J.C.R. Licklider
was hired and developed a working group he called
the "Intergalactic Network", a precursor
to the ARPANet.
In 1964, researchers at Dartmouth
developed the Dartmouth Time Sharing System for
distributed users of large computer systems. The
same year, at MIT, a research group supported
by General Electric and Bell Labs used a computer
(DEC's PDP-8) to route and manage telephone connections.
Throughout the 1960s Leonard Kleinrock,
Paul Baran and Donald Davies independently conceptualized
and developed network systems which used datagrams
or packets that could be used in a packet switched
network between computer systems.
The first widely used PSTN switch
that used true computer control was the Western
Electric 1ESS switch, introduced in 1965.
In 1969 the University of California
at Los Angeles, SRI (in Stanford), University
of California at Santa Barbara, and the University
of Utah were connected as the beginning of the
ARPANet network using 50 kbit/s circuits. Commercial
services using X.25, an alternative architecture
to the TCP/IP suite, were deployed in 1972.
Computer networks, and the technologies
needed to connect and communicate through and
between them, continue to drive computer hardware,
software, and peripherals industries. This expansion
is mirrored by growth in the numbers and types
of users of networks from the researcher to the
home user.
Today, computer networks are the core
of modern communication. The scope of communication
has increased significantly in the past decade
and this boom in communications would not have
been possible without the progressively advancing
computer network.
Networking methods
Networking is a complex part of computing that
makes up most of the IT Industry. Without networks,
almost all communication in the world would cease
to happen. It is because of networking that telephones,
televisions, the internet, etc. work.
One way to categorize computer networks
are by their geographic scope, although many real-world
networks interconnect Local Area Networks (LAN)
via Wide Area Networks (WAN). These two (broad)
types are:
Local area network (LAN)
A local area network is a network that spans a
relatively small space and provides services to
a small amount of people. Depending on the amount
of people that use a Local Area Network, a peer-to-peer
or client-server method of networking may be used.
A peer-to-peer network is where each client shares
their resources with other workstations in the
network. Examples of peer-to-peer networks are:
Small office networks where resource use is minimal
and a home network. A client-server network is
where every client is connected to the server
and each other. Client-server networks use servers
in different capacities. These can be classified
into two types: Single-service servers, where
the server performs one task such as file server,
print server, etc.; while other servers can not
only perform in the capacity of file servers and
print servers, but they also conduct calculations
and use these to provide information to clients
(Web/Intranet Server). Computers are linked via
Ethernet Cable, can be joined either directly
(one computer to another), or via a network hub
that allows multiple connections.
Historically, LANs have featured much
higher speeds than WANs. This is not necessarily
the case when the WAN technology appears as Metro
Ethernet, implemented over optical transmission
systems.
Wide area network (WAN)
A wide area network is a network where a wide
variety of resources are deployed across a large
domestic area or internationally. An example of
this is a multinational business that uses a WAN
to interconnect their offices in different countries.
The largest and best example of a WAN is the Internet,
which is the largest network in the world. The
PSTN (Public Switched Telephone Network) also
is an extremely large network that is converging
to use Internet technologies, although not necessarily
through the public Internet.
A Wide Area Network involves communication
through the use of a wide range of different technologies.
These technologies include Point-to-Point WANs
such as Point-to-Point Protocol (PPP) and High-Level
Data Link Control (HLDC), Frame Relay, ATM (Asynchronous
Transfer Mode) and Sonet (Synchronous Optical
Network). The difference between the WAN technologies
is based on the switching capabilities they perform
and the speed at which sending and receiving bits
of information (data) occur.
For more information on WANs, see
Frame Relay, ATM and Sonet.
Wireless networks (WLAN, WWAN)
A wireless network is basically the same as a
LAN or a WAN but there are no wires between hosts
and servers. The data is transferred over sets
of radio transceivers. These types of networks
are beneficial when it is too costly or inconvenient
to run the necessary cables. For more information,
see Wireless LAN and Wireless wide area network
In order for communication to take
place between computers, mediums must be used.
These mediums include Protocols, Physical Routers
and Ethernet, etc. This is covered by Open Systems
Interconnection which comprises all the processes
that make information transport possible.
The network topology defines the way
in which computers, printers, and other devices
are connected. A network topology describes the
layout of the wire and devices as well as the
paths used by data transmissions. Commonly referred
to as a linear bus, all the devices on a bus topology
are connected by one single cable.
|
