What is network?
A network consists of two or more computers that are linked in order to share resources (such as printer and CDs) exchange files or allow electronic communication. Or network is simply a collection of computers or other hardware devices that are connected together either physically or logically using special hardware and software .which allow them to exchange information and cooperate.
Computer networks supports many applications and services such as access the world wide web digital video ,digital audio ,shared use of application and storage servers printers and fax machines ,and use of email and instant messaging applications.
The idea of ARPANET one of the earliest computer networks was proposed by Leonard kleinrock in 1961, in his paper title information flow in large communication nets
ARPANET was one of the first computer networks to use packet switching development of ARPANET started in 1966 and the first two nodes UCLA and STI (standford research institute) were connected, officially starting ARPANET in 1969.
TYPES OF NETWORKS
LAN (local area
network)
LANs are the most frequently discusses networks one of most common one of the simplest type of network, it is connected rooms within a buildings .LANs connected groups of computers and low voltage devices together across short distance.
LAN is a group of computer and associated devices that share a common communications line or wireless link to a server LAN data with speed of several megabits /s 10*10 up to 6 times bits LAN is usually link within a limited geographical because they must connected by cable ,which is quite expensive .people working in LAN .get more capabilities in data processing ,work processing and other information exchange .LAN is set up to when team members need to share software and hardware resources with each other but not with the outside world ,typical software resources include officially documents user manuals , employee handbook etc.
CHARACTRISTICS OF LAN
It is a private network so an outside regulatory body never controls it
High data transmission rate.
Easy physical connected of computers in a network
High degree of interconnection between computers
You can use the different topology mainly bus and ring in LAN
The communication quality is better in LAN the transmission error rate are low
WIDE AREA NETWORK
(WAN)
The term wide area network (WAN) used to describe a computer network spanning a regional or global area. The regional centers are connected to headquarters through WAN.
The first known WAN was created by the U.S air force in the late 1950`s to interconnect sites in the semi-automatic ground environment (SAGE) radar defense system an enormous network of dedicated phone lines telephones and modems linked the sites together.
A wide area network is collection of local area network that communicates with one other; a WAN is essentially a network of networks with the internet, the worlds largest WAN. These networks are often established by service provides that then lease their WAN to businesses, schools, governments or the public, these customers can use the network to relay and store data or communicate with other users, no matter their location as long as they have access to the established WAN, access can be granted via different links, such as virtual private networks or lines wireless networks, cellular networks or internet access.
WAN connections can include wired and wireless technologies .wired WAN services can consists of multiprotocol label switching T2s carrier Ethernet and commercial broadband internet links wireless .WAN technologies can include cellular data networks like 4G LTE ,as well as public Wi-Fi or satellite networks .
MAN (METROPOLITAN
AREA NETWORK)
A metropolitan area network is a biggest version of local area network (LAN) uses same technologies.
The man network is a high speed network that covers largest geographic area such as city (tens of kilometers) or districts than local area network but smaller than wide area network .the term is applied to the single networks or it can be a way of connecting certain number of LAN in a more extensive network so that resources can share from LAN to LAN and from device to device.
The MAN can be used to provide services including telecoms, internet access, television and CCTV to businesses and citizens in these metropolitan areas. Now days, MAN network are connecting a number of campus LAN networks which are designed in hierarchical structure such as access, distribution and core.
WIREDLESS NET WORK
Wireless communication plays a significant role in day to day life .besides communication wireless technology has become an integral part of our daily activities the transmission of data or information from one place to another wirelessly is refereed as wireless communication .this provides an exchange of data without any conductor through RF and radio signals. The information is transmitted across the devices over some meters to hundreds of kilometers through well defined channels.
WIRELESS TECHNOLOGIES
Deferent types of signals are used in communication between the devices for wireless transmission of data.
TERRESTRIAL MICROWAVE
Terrestrial microwave communication use earth based transmitters and receivers resembling satellite dishes. Microwave is the form of electromagnetic transmission used in wireless communication system.. These are widely used for long distance communications and are relatively less expensive. But microwave does not pass through buildings and whether affects the signal transmission .Microwaves from your mobiles phones can affect parts of your brain.
RADIO AND SPREAD SPECTRUM TECHNOLOGIES.
Open radio, communication was one of the first wireless technologies to first wide spread use, and it still serves a purpose today, Ham radio enthusiasts share information and serve as emergency communication aids during disasters with their power full amateur broadcasting equipment, and even communicate digital data over the radio spectrum the Wi –Fi .open standards wireless radio wave technology by IEEE 802.11
CELLULAR
Cellular network use encrypted radio links modulated to allow many different users to communicate across a single frequency band. The systems divide the region covered in to multiple geographic areas. Each area has low -power transmitter or radio relay antenna device to relay cells from one area to the next area. Data transmission over cellular networks is possible with modern 4G system capable of speed approaching that of wired DSL or cable connection.
COMMUNICARION
SATELITES
A communication satellite is another wireless technology that has found wide speeds use in specialize situations. these device communicate via microwave radio waves which are not deflected by the earth `s atmosphere the satellites are stationed in space typically in geosynchronous orbit 35400 km (22,000mi) above the equator these earth orbiting systems are capable of receiving and relaying voice, data and TV signals.
MANET
MANET stands for mobile adhoc network also called as wireless adhoc network that usually has a routable network in environment on top of link layer ad hoc network .they consist of set of mobile nodes connected wirelessly in a self configured, self healing network without having a fixed infrastructure. Since the node in MANET move around the wireless links break and establish frequently furthermore most of mobiles nodes are resources limited in computing capability and battery power and therefore traditional computing content routing protocols are not suitable for MANET .several adhoc routing protocols have been proposed for each node acting as router and maintaining routing information.
The main challenge for the MANET is to equipped each devices to continuously maintain the information required to properly route traffic .MANET consist of a peer-to-peer self -forming, self –healing network MANET .the characteristic of MANET namely infrastructure less ,wireless medium dynamic topology ,distributed cooperation and dynamic network .create vulnerability to various kinds of security attacks .each of node is wireless interface to commutate with each other nodes these works are fully distributed and can works at any place without the help of any fixed infrastructure as access point.
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