Bit torrent: A technical pyramid scheme?

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Bit torrent: A technical pyramid scheme?

Post by MovieStuff » Sun Aug 08, 2010 2:56 am

I am delving into uncharted territory for me but my understanding about how bit torrent works is that, when you sign up to be part of a bit torrent network, then you have essentially have the same file on your PC that, perhaps, a hundred other people also have. And when someone wants to down load that file, then all the PCs in the torrent network act in unison to handle the larger data load.

Now, assuming this is how it works (and I could be wayyyyyy off the mark) then it seems to me that such a transfer would never be any faster than moving the same data from one hard drive in your PC to another in the same PC. Not saying that's slow but, clearly, there's no way it could be any faster than what your drive can write. That's okay if that's the case.

But the other thing that seems apparent is that the first person to try and download a particular file gets screwed, time wise, because the file does not yet exist on multiple servers. So the 100th guy to download gets all the benefits of what those before him didn't. At what point does the torrent network come to a screeching halt because everyone smarts up and decides to just wait for the info to be on multiple servers?

Again, I may have the technology wrong but I think my conclusions are still accurate about the first guy getting the short end of the stick.

What say you with bigger brains than me?

Roger

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Re: Bit torrent: A technical pyramid scheme?

Post by christoph » Sun Aug 08, 2010 6:06 am

hi roger,

bittorrent will never be as fast as a direct copy from sata drive to sata drive in the same PC - it is a network protocol, so it was never intended to be used that way.

in reality, the distribution speed is mainly limited by the upload speed of the first seeder. if i start a torrent with 10MB and have an upload speed of 100KB/sec, it will take at least 100 seconds for the first person to download the file.. that's simply the nature of the beast.
like if i upload it to a webserver through ftp, it obviously will take the same 100 sec as well. downloading from the webserver would be quite fast for most people because usually people have asymetrical lines. like i have about 1.5MB/sec, so the 10MB file would be downloaded in 7 seconds. so why not use a webserver? well, because if you have 25GB files and 100people downloading it, some poor guy would have to pay for the traffic (a lot).

with bittorrent, theorectically the first person would need 100sec to download, but the second will have the 100KB/sec upload of the seeder plus the upload of the first downloader, so let's say 200KB/sec, or he only has to wait 50sec.
the third will have a download speed of 300KB/sec, so it's even faster.
this is actually a good thing, and nobody is cheated because everybody agrees to help distributing the torrent. also in reality, for large torrents it will work different. lets say it takes 24hours to download the fill file by one peer. but while he's downloading, he's uploading parts to the second peer, and the second peer will download different parts from the original seeders, which he will share with the first peer. now with 5 peers starting at the same time, this will result in all 5 having the full download after nearly the same time, because it's not that the first guy gets 100KB/sec and the 5th 500KB/sec, but everybody will have 100KB/sec from different peers (given they have similar internet connections).. it will take slightly longer then 24hours, but not a lot, and nobody has to pay for the bandwith because local connections are usually flatrate these days.

now if a sixed guy starts downloading after 30hours, he'll get the full upload speed of all six people (original seeders and five downloaders) if they are still seeding, so obviously he'll finish in about the sixth of the time (given equal connections). i still wouldn't say the first five guys get screwed because they got the download for free and earlier guy number six.

the hole idea is really that everybody helps distributing the file, and unless you're paying for traffic locally on your ISP nobody gets any disadvantage.

++ c.

ps : another really nice thing is that it has error correction, so if a part is corrupt you don't have to download the full 25GB again, but nly a few KB. this is specially important on files like installers.

pps: wikipedia has a much better explanation (as usual)
http://en.wikipedia.org/wiki/BitTorrent_%28protocol%29

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Re: Bit torrent: A technical pyramid scheme?

Post by aj » Sun Aug 08, 2010 11:15 am

MovieStuff wrote:
Again, I may have the technology wrong but I think my conclusions are still accurate about the first guy getting the short end of the stick.

What say you with bigger brains than me?

Roger
Seeders are frequently on high bandwidth networks. Such as campus or university. The first downloaders don't get the bad deal there.
Others have fibre to the home which are become symetrical in speed quickly.

Only with small groups like PTC where all are on ADSL or small bandwidth getting the set-up going is a bit of a hassle.

Main advantage is the shared burden when it is running, the use is free as the participants already have the storage and connection.
Should the content be contrabande finding the hosters can be a bit of a problem. I.e. many and everywhere.

If everybody waits nothing will happen. It is a bit like being the Samaritan, blood or organ donor, the guy who saves somebody from the water or yells when a car is about to hit a fellowman.

Downloaders would need to go to a store or need get a physical bearer. Also they could divert to paid service USENET hosters with long retention times and high bandwidth. Still somebody would be required to upload useful data, through a slow line. But then these get credits for that. :)
Kind regards,

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Re: Bit torrent: A technical pyramid scheme?

Post by richard p. t. » Sun Aug 08, 2010 2:35 pm

and of course, in a typical pyramid scheme it is the early participants that do well, and the later ones that get ripped off.
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Re: Bit torrent: A technical pyramid scheme?

Post by reflex » Sun Aug 08, 2010 8:19 pm

Bit torrent is an efficient way to share a large video file or disc image to a large number of users. It makes far more sense (bandwidth wise) to seed a torrent than to have 1000 people download it directly from your site.

Actually, the load on the initial seeder doesn't have to be extremely high, because each large file is split into pieces that are torrented separately.

I might only have 10% of your file copied to my machine, but as long as I have a few complete pieces, my computer will start sharing those completed segments of the file with other peers who request the same file.

That's the key to bit torrent. It's distributed. Chances are that my copy of a file will come from several dozen different users.

But yeah, if you're an early seeder of a relatively obscure torrent, you will end up having to seed more. However, popular torrents are often surprisingly efficient (I recently used an official torrent to get the latest Jolicloud OS, and it was running flat-out within an hour of being available because there were so many seeders and peers).
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Re: Bit torrent: A technical pyramid scheme?

Post by MovieStuff » Sun Aug 08, 2010 8:58 pm

richard p. t. wrote:and of course, in a typical pyramid scheme it is the early participants that do well, and the later ones that get ripped off.
Yeah. I saw it as a kind of "inverted" pyramid scheme where the early investors don't get as good a deal as later investors. Based on the explanations so far, that seems like a pretty fair description. I understand the logic behind it and it does seem efficient but, still, it's more efficient for those that come to the party late than those that arrive early. ;)

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Re: Bit torrent: A technical pyramid scheme?

Post by Sparky » Sun Aug 08, 2010 9:07 pm

Not if you arrive too late and everyone's gone home (stopped seeding) though ;-)
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Re: Bit torrent: A technical pyramid scheme?

Post by MovieStuff » Sun Aug 08, 2010 9:15 pm

Sparky wrote:Not if you arrive too late and everyone's gone home (stopped seeding) though ;-)
Mark
Well, that brings up a related question. If you are part of a torrent network, then your PC essentially becomes part of the server network. So don't you have to leave your PC active all the time so others can download part of the file from your system? What happens if everyone on the network has their system turned off? Does that mean you can't download or that, perhaps, you have to download the whole file from a remote server at a much slower pace? What happens if you are doing that and then 12 people in the torrent network suddenly log on and make the file available. Does the download suddenly speed up?

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Re: Bit torrent: A technical pyramid scheme?

Post by Sparky » Sun Aug 08, 2010 10:16 pm

Hi Roger, yes, yes and yes!
If there are no seeds or peers you can't download, so it relies on people playing fair and not just switching their machines off after they finished downloading. In fact I think the tracker monitors this and penalises those who haven't seeded enough with lower bandwidth. Mark

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Re: Bit torrent: A technical pyramid scheme?

Post by christoph » Sun Aug 08, 2010 10:17 pm

MovieStuff wrote:Yeah. I saw it as a kind of "inverted" pyramid scheme where the early investors don't get as good a deal as later investors. Based on the explanations so far, that seems like a pretty fair description.
i don't quite understand why you're thinking about a "deal" and "investors" etc, everybody benefits from sharing a torrent, and it doesn't really cost anybody anything. it has nothing to do with an inverted pyramid scheme either (ie no exponentional grow/shrinkage). if everybody is on a similar network connection, each pear will have uploaded about the same amount as downloaded anyway (ratio of 1 in the end on a large torrent).
MovieStuff wrote:Well, that brings up a related question. If you are part of a torrent network, then your PC essentially becomes part of the server network. So don't you have to leave your PC active all the time so others can download part of the file from your system?
yes, it's a peer to peer file sharing protocol, so obviously if all the peers are shut down there's nothing to download from.
What happens if everyone on the network has their system turned off?
you will have to wait until somebody that has a part of the file you don't have already comes online again.
Does that mean you can't download or that, perhaps, you have to download the whole file from a remote server at a much slower pace?
as said, there is no central server with the file data, so you'll have to wait.
What happens if you are doing that and then 12 people in the torrent network suddenly log on and make the file available. Does the download suddenly speed up?
jup, it takes a minute or so to re-etabilsh the connections but then it will resume automatically again. that's one of the big strenghts of the system really, it's handles interruptions and resumes very gracefully.

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Re: Bit torrent: A technical pyramid scheme?

Post by MovieStuff » Sun Aug 08, 2010 10:33 pm

christoph wrote: i don't quite understand why you're thinking about a "deal" and "investors" etc, everybody benefits from sharing a torrent, and it doesn't really cost anybody anything. it has nothing to do with an inverted pyramid scheme either (ie no exponentional grow/shrinkage). if everybody is on a similar network connection, each pear will have uploaded about the same amount as downloaded anyway (ratio of 1 in the end on a large torrent).
Not as it has been explained. If you have the original file and no one else in the network has it, then how does it get onto everyone else's PC's throughout the system? Don't you have to upload the whole file and spread it across multiple PCs for anyone after that point to benefit from the faster download time? And if you want a file that exists only on one PC and are the first in the network to download it, doesn't that take longer than someone that waits until it is spread across multiple PCs? In essence, not all the participants get the same benefits. Those that come later and only download experience more benefits that those who download early or upload. At least as I understand it from this discussion.

Roger

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Re: Bit torrent: A technical pyramid scheme?

Post by Sparky » Sun Aug 08, 2010 10:57 pm

Hi Roger, you don't seem to understand at all. It's not about "benefits" but about sharing a file with lots of others without having them all download it from just you. You could put it on an FTP server and people could download it but then you'd be hammering your bandwidth and it might cost you. This way you only really need to upload it once and the people who download it then share it on. Say I have a file, broken into 4 blocks, and 4 people start downloading it, they will each be assigned different blocks, then when they've downloaded their first block they needn't download from me anymore because they can download from each other. It's all done automatically, is fail safe and very robust. I'm really impressed actually :D

Why do you have an issue with something that works very well?

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Re: Bit torrent: A technical pyramid scheme?

Post by christoph » Sun Aug 08, 2010 11:00 pm

MovieStuff wrote:Don't you have to upload the whole file and spread it across multiple PCs for anyone after that point to benefit from the faster download time?
not really, if you upload only 50%, everybody can already spread those 50%. it could even be that you seed 50% to peer1 and the second 50% to peer2 and then log off, and the torrent would still be fully functional and eventually complete to 100% for everybody. if the original seeder logs off before he seeded all parts to at least somebody then the torrent will never complete of course.

but i think i see what you mean.. if 10 people start downloading at 6am and the download takes 12hours, they will all complete about 6pm. if somebody joins around 1pm he will probably also finish around 6pm, and if somebody starts at 6pm he might finish around 7pm. so you could say the last guy got the biggest benefits, but personally i don't see it like that because the other guys have the file before him, and it wasnt a bigger effort or anything.. most people have their computer running 10hours a day anyway for email, skype, facebook etc.

++ c.

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Re: Bit torrent: A technical pyramid scheme?

Post by MovieStuff » Mon Aug 09, 2010 12:08 am

Sparky wrote: Why do you have an issue with something that works very well?

Mark
I don't have an issue with it at all. I understand that it is a great way to share files if your goal is to share files with a number of people and you want it to be convenient for them, even if it isn't necessarily convenient for you in the beginning. I am actually considering it myself, which is why I'm trying to understand the ups and downs. I was merely making an observation that those who join the network later don't really have to contribute if all they want to do is see the files that are already on the network. Am I right? If so, that would qualify as a benefit for late comers to the party that just want to mooch. Is there a way to monitor who plays nice and who doesn't?

Roger

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Re: Bit torrent: A technical pyramid scheme?

Post by MovieStuff » Mon Aug 09, 2010 12:16 am

christoph wrote: but i think i see what you mean.. if 10 people start downloading at 6am and the download takes 12hours, they will all complete about 6pm. if somebody joins around 1pm he will probably also finish around 6pm, and if somebody starts at 6pm he might finish around 7pm. so you could say the last guy got the biggest benefits, but personally i don't see it like that because the other guys have the file before him, and it wasnt a bigger effort or anything.. most people have their computer running 10hours a day anyway for email, skype, facebook etc.

++ c.
Well..... if the initial 12 hour download isn't that big a deal, then why bother with bit torrent in the first place? Because the whole point of using the bit torrent is that it allows someone to eventually download faster than normal. But that someone doesn't have to contribute to the cause, so to speak. So he benefits from the previous effort of others if all he wants to do is watch what's on the network. Or am I still not understanding how this works (entirely possible).

Roger

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