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The key to the efficiency of a network is good message routing.

Focusing on electrical networks, most analog ones make inefficient use of communication links because truly dynamicrouting is difficult, if not impossible, to obtain. In radio networks, such as commercial television, each station has adedicated portion of the electromagnetic spectrum, and this spectrum cannot be shared with other stations or used in anyother than the regulated way. The telephone network is more dynamic, but once it establishes a call the path through thenetwork is fixed. The users of that path control its use, and may not make efficient use of it (long pauses while one personthinks, for example). Telephone network customers would be quite upset if the telephone company momentarily disconnected the pathso that someone else could use it. This kind of connection through a network—fixed for the duration of thecommunication session—is known as a circuit-switched connection.

During the 1960s, it was becoming clear that not only was digital communication technically superior, but also that thewide variety of communication modes—computer login, file transfer, and electronic mail—needed a different approachthan point-to-point. The notion of computer networks was born then, and what was then called the ARPANET, now called theInternet, was born. Computer networks elaborate the basic network model by subdividing messages into smaller chunks called packets ( [link] ). The rationale for the network enforcing smaller transmissions wasthat large file transfers would consume network resources all along the route, and, because of the long transmission time, acommunication failure might require retransmission of the entire file. By creating packets, each of which has its own address andis routed independently of others, the network can better manage congestion. The analogy is that the postal service, rather thansending a long letter in the envelope you provide, opens the envelope, places each page in a separate envelope, and using theaddress on your envelope, addresses each page's envelope accordingly, and mails them separately. The network does need tomake sure packet sequence (page numbering) is maintained, and the network exit point must reassemble the original messageaccordingly.

Long messages, such as files, are broken into separate packets, then transmitted over computer networks. A packet, like aletter, contains the destination address, the return address (transmitter address), and the data. The data includes themessage part and a sequence number identifying its order in the transmitted message.

Communications networks are now categorized according to whether they use packets or not. A system like the telephone network issaid to be circuit switched : The network establishes a fixed route that lasts the entire duration of the message. Circuit switching has theadvantage that once the route is determined, the users can use the capacity provided them however they like. Its maindisadvantage is that the users may not use their capacity efficiently, clogging network links and nodes along the way. Packet-switched networks continuously monitor network utilization, and route messages accordingly. Thus,messages can, on the average, be delivered efficiently, but the network cannot guarantee a specific amount of capacity to theusers.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Intro to the internet. OpenStax CNX. Oct 12, 2007 Download for free at http://cnx.org/content/col10469/1.3
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