Networking 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. Computer networking is sometimes
considered a sub-discipline of telecommunications, computer
science, information technology and/or computer engineering. Computer networks rely
heavily upon the theoretical and practical application of these scientific and
engineering disciplines. There are three types of networks: 1.Internet.
2.Intranet. 3.Extranet. A computer network is any set of computers or devices
connected to each other with the ability to exchange data. All networks are
interconnected to allow communication with a variety of different kinds of
media, including twisted-pair copper wire cable, coaxial
cable, optical fiber, power lines and various wireless
technologies. The devices can be separated by a few meters (e.g. via Bluetooth) or
nearly unlimited distances (e.g. via the interconnections of the Internet).
Views of Networks: Users and network administrators often have
different views of their networks. Often, users who 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
connection 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 private administration usually by an enterprise,
and is only accessible by authorized users (e.g. employees). Intranets do not
have to be connected to the Internet, but generally have a limited connection.
An extranet
is an extension of an intranet that allows secure communications to users
outside of the intranet (e.g. business partners, customers). 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.
When used for gaming one computer will have to be the server while the others
play through it.
History of Computer Networks: Before the advent of computer networks that
were based upon some type of telecommunications system, communication between
calculation machines and history of computer hardware 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 and arguably in even earlier networks using visual signals. The Victorian Internet. In September 1940 George Stibitz used a teletype machine to send
instructions for a problem set from his Model 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 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 Packet information technology that could be used in
a network between computer systems. 1965 Thomas Merrill and Lawrence G. Roberts
created the first wide area network (WAN). The first widely used PSTN switch that used true computer
control was the Western Electric 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 were
deployed in 1972, and later used as an underlying infrastructure for expanding
TCP/IP networks. 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. 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. 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: One way to categorize computer networks is
by their geographic scope, although many real-world networks interconnect Local Area Networks (LAN) via Wide
Area Networks (WAN) and wireless networks (WWAN). These three (broad) types
are:
a)
Local area
network (LAN): A local area network is a network that spans
a relatively small space and provides services to a small number of people. 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:
1. Single-service servers
2. Print server
The server performs one task such as file server, while
other servers can not only perform in the capacity of file servers and print
servers, but also can conduct calculations and use them to provide information
to clients (Web/Intranet Server). Computers may be connected in many different
ways, including Ethernet cables, Wireless networks, or other types of wires
such as power lines or phone lines. The ITU-T G.hn standard is an
example of a technology that provides high-speed (up to 1 Gbit/s) local area
networking over existing home wiring (power lines, phone lines and coaxial cables). By :- Jitendra sir alpha
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b)
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 a network composed of many smaller
networks. The Internet is considered 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 (HDLC), 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.
c)
Metropolitan
area network (MAN): A metropolitan network is a
network that is too large for even the largest of LAN's but is not on the scale
of a WAN. It also integrates two or more LAN networks over a specific
geographical area ( usually a city ) so as to increase the network and the flow
of communications. The LAN's in question would usually be connected via "
backbone " lines.
d)
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. The media
access protocols for LANs come from the IEEE. The most common IEEE 802.11
WLANs cover, depending on antennas, ranges from hundreds of meters to a few
kilometers. For larger areas, either communications satellites of various
types, cellular radio, or wireless local loop (IEEE 802.16)
all have advantages and disadvantages. Depending on the type of mobility
needed, the relevant standards may come from the IETF or the ITU.
Network topology: The network
topology defines the way in which computers, printers, and other devices
are connected, physically and logically. A network topology describes the
layout of the wire and devices as well as the paths used by data transmissions.
Network topology has two types:
- Physical
- logical
Commonly used topologies include:
- Bus
- Star
- Tree
(hierarchical)
- Linear
- Ring
- Mesh
- partially
connected
- fully
connected (sometimes known as fully
redundant)
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