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Bram Cohen on BitTorrent “Bandwidth Fundamentals”

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Bram Cohen on BitTorrent “Bandwidth Fundamentals”

Postby Overnet User » Thu Jul 09, 2009 12:45 am

BitTorrent creator explains just why BitTorrent works so well, that the formula is simply bytes downloaded = bytes uploaded. I’ve always found Bram Cohen, author of the BitTorrent protocol, very fascinating, perhaps mainly because he’s allowed myself and countless others the ability to share content in ways still yet to be imagined.
So whenever he shares his thoughts on BitTorrent I always sit up and take notice.

In this case it’s nothing spectacular, but he does give a simple explanation of why BitTorrent performs so well why dispelling the myth that content popularity drives download speeds.
He writes:

There’s a classic fallacy because if one person stands up during a concert they get a better view, then if everybody stood up during a concert they’d all get a better view. This is of course is not true – they wind up slightly worse off by all standing, because they all compete with each other for a view. The same thing happens with downloading from a server. In general, web servers will give about the same rate to every client downloading from them, so if you open many more connections than everybody else you get a greater proportion of the bandwidth and hence a better rate. But you do so simply by taking bandwidth from other downloaders. The overall supply of upload is unchange, it’s simply being shuffled around. If everybody does the same thing it results in overall slightly worse performance and you’re basically back where you started, but with a bunch of headaches tacked on.

So why does BitTorrent perform so well? Quite simply, because it does a better job of finding more places to do uploading. Any peer which is downloading is in general willing to upload as well, and their uplink is usually unutilized, so if you can get a peer to start uploading as soon as it starts downloading, and keep uploading as long as possible, and saturate its link while it’s uploading, then overall performance will be better. It doesn’t necessarily help to transfer over more connections, or make more different things available at the same time, or use error correcting codes. In fact, all of those are a complex tradeoff between benefits and costs, with the net result being that small amounts of them can help reliability and robustness, but in general it’s good to keep things simple and be polite to the network.
On the internet, the formula is bytes downloaded = bytes uploaded. It’s that simple.
Indeed it is.


Bram Cohen on BitTorrent “Bandwidth Fundamentals”
Last edited by Overnet User on Thu Jul 09, 2009 12:34 pm, edited 1 time in total.
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Re: Bram Cohen on BitTorrent “Bandwidth Fundamentals”

Postby IneptVagrant » Thu Jul 09, 2009 6:24 am

AVG is throwing a virus alert on zeropaid.com

Worm/Small
http://www.avg.com/virbase-app?idn=%40EID_Fi_vir

But it doesn't return any info, so I'm thinking its BS
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Re: Bram Cohen on BitTorrent “Bandwidth Fundamentals”

Postby multivariable » Thu Jul 09, 2009 7:50 am

IneptVagrant wrote:AVG is throwing a virus alert on zeropaid.com

NOD32 is doing it too.


Overnet User wrote:I’ve always found Bram Cohen, author of the BitTorrent protocol, very fascinating...

You've always found Bram Cohen fascinating, have you donkeyboy?
Or perhaps it's the actual author of the article that has always found him so?
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Re: Bram Cohen on BitTorrent “Bandwidth Fundamentals”

Postby Fartingbob » Thu Jul 09, 2009 8:07 am

AntiVir doesnt like the page either. Has zeropaid sunk to a new low?
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Re: Bram Cohen on BitTorrent “Bandwidth Fundamentals”

Postby Noise » Thu Jul 09, 2009 9:56 am

perhaps the site was hacked? avast! hates it too, btw...
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Re: Bram Cohen on BitTorrent “Bandwidth Fundamentals”

Postby c0ld » Thu Jul 09, 2009 10:00 am

because he’s allowed myself and countless others the ability to share content in ways still yet to be imagined.
That makes no sense whatsoever.
There’s a classic fallacy because if one person stands up during a concert they get a better view, then if everybody stood up during a concert they’d all get a better view. This is of course is not true – they wind up slightly worse off by all standing, because they all compete with each other for a view. The same thing happens with downloading from a server. In general, web servers will give about the same rate to every client downloading from them, so if you open many more connections than everybody else you get a greater proportion of the bandwidth and hence a better rate. But you do so simply by taking bandwidth from other downloaders. The overall supply of upload is unchange, it’s simply being shuffled around. If everybody does the same thing it results in overall slightly worse performance and you’re basically back where you started, but with a bunch of headaches tacked on.

This analogy is about a year out of date on some private trackers. The problem is no longer some people downloading more than they should, but rather people using seedboxes to upload more than they should to boost their ratio. The analog still applies though. People with seedboxes 'stand up' and if everyone were to seedbox up, we'd all be back to square one. Further, 'The overall supply of download is still the same, it's simply being shuffled around' meaning that most people with ordinary connections can no longer maintain their ratio because seedboxes flood the swarm.
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Re: Bram Cohen on BitTorrent “Bandwidth Fundamentals”

Postby Overnet User » Thu Jul 09, 2009 12:38 pm

multivariable wrote:
IneptVagrant wrote:AVG is throwing a virus alert on zeropaid.com

NOD32 is doing it too.
Overnet User wrote:I’ve always found Bram Cohen, author of the BitTorrent protocol, very fascinating...

You've always found Bram Cohen fascinating, have you donkeyboy?
Or perhaps it's the actual author of the article that has always found him so?


Simply news here, I personally haven't followed the guy much at all other than using a modified Azureus client very often. Since he is behind the technology or having created bittorrent protocol, and since I use it, I guess you can say that many bittorrent users follow him.
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