Upload policy

[Gruzilkin]

I was just wondering how uTorrent works, couldn't find it in FAQ/forum

when a seeder has full file, and he upload to 5 users for example... and the seeder(just as any client) has information about other clients pieces, right? if not, how do they show availability bar then

so, assuming that seeder knows, which peaces aren't available in the swarm, will it give priority to them during uploading ?

for example... seeder A has full file, client B has from 25% to 75%, and client C has from 50% to 100%... seeder A then will be more efficient, if he uploads only 0-25% part of the file, because 25-100% part of the file is already present in the swarm (on B and C)

and so, the question... does uTorrent works this way?

in the FAQ it is mentioned as SuperSeed mode... but that's a bit different, you need to be the only seed in the swarm, and what I described - may have multiple seeds...

I already see two problems here... client doesn't know what pieces other clients have or that it already works this way

if it is possible, it would be great to have a upload mode, when a client doesn't spend upload bandwith on a file, that has lot's of peers and huge availability (even though there may be no seeders in the swarm)... this way, most of the traffic will be between peers, while seeder will only ensure, that the swarm has availability >1... and will spend their upload bandwith only when it is crucial to maintain torrent

as for some examples... I have 5Mbit/s upload bandwith with unlimited traffic and I don't mind uploading at such speed... I just don't want to do it 24/7... I may have other torrents to download or something else to do with my upload bandwith

so what's wrong with having a feature, which could support torrents (that otherwise would be dead) and also minimize load on seeders?

[Switeck]

µTorrent is supposed to make some effort to choose what to upload, but I think the downloaders are also able to choose what parts they want to download...which if the download side is poorly written may mean downloaders are requesting redundant parts from seeds that they could easily get from other peers.

µTorrent may not be able to do much as there's so many other BitTorrent clients connected on a typical torrent. If they are all making bad download choices, then µTorrent only has a choice of uploading or not uploading to them.

[Gruzilkin]

µTorrent may not be able to do much as there's so many other BitTorrent clients connected on a typical torrent. If they are all making bad download choices, then µTorrent only has a choice of uploading or not uploading to them.

Then it can upload only those parts, that are not redundant or give more bandwith to them... make some sort of priority

what is my idea... when you download a torrent, you are just an ordinary peer... when you get full torrent, you become a seeder, until you seed 1.5 (or 1.05, 1.0 - doesn't matter), and then you disconnect... so maybe, instead of disconnecting, you may become some sort of backup/extra seeder, who uploads only when availability is <1

[Switeck]

For µTorrent to do that, it has to break compatibility with how seeding works in the BitTorrent protocol.

While running in such a mode, it would appear to be a peer (that wants nothing) not a seed.

Super/Initial seeding already does this...but it has serious stalling issues due to other clients refusing to select the limited offering of torrent pieces.

[Gruzilkin]

this mode can be something like a peer, who claims to have only those pieces, that are necessary for the swarm to have availability <1 (1-2% of a torrent, for example) ... why does it break BitTorrent protocol?

I read about super seeding... what's its main goal? - to minimize load on initial seeder... the same mechanism should work after download too, imho... the more you load seeders - the more chances that they disconnect

such mode would encourage people to keep seeding, because they will know, that they won't be "bothered" unless it is really necessary

[Ultima]

I'm having trouble understanding something here... how exactly would this work with multiple seeds? Your example with the 0-25% and 25-100% are only relevant if there is a single seed. If there are other seeds in the swarm, what happens if they all decide to behave identically and share only 0-25%? Then you get an extremely heavily seeded first 25%, and sparsely shared 25-100%, which is bad for the swarm.

As far as I'm understanding it, this request is not unlike asking why we can't use super-seeding with multiple seeds ;o

[Gruzilkin]

if there are multiple seeds with 0-25% of a file... if they behave identically, then only ONE of them will share 0-25% pieces... because others won't seed that part, if it is shared by at least one client

or they may be another behavour, and I like it better:

let's say, that there are 3 such "backup seeds", and 2 peers who have 25-100% part of torrent, and they need 0-25%... each "backup seed" knows, that the network needs 0-25% part, but he can make available only some random piece of that 0-25% and then wait for other "backup seeds" to update... and because they also won't make whole 0-25% piece available, but just a small random part of it (and definitly not the one, that was already randomly chosen by another "backup seed", because network doesn't need it anymore), all these 3 "backup seeds" are likely to SHARE that 0-25% piece (approx 1/3 each)

[Ultima]

Okay, so what about a mixed population of seeds, some behaving normally, and some behaving as you recommend? Then these seeds don't need to share at all? It all sounds very selfish to me. In essence, you're basically saying that only peers or seeds who don't behave as you're suggesting should take the bandwidth load. If all seeds were to behave in this way, then everyone would be downloading the same torrent for days. If I had a 5mbit unlimited upload bandwidth, this kind of behavior would be the least of my worries.

[Gruzilkin]

yes, when there's a mixed population of normal seeds/peers and "backup seeds", "backup seeds" - don't upload at all... and it's not selfish, because they have already done their work and have ratio >1 (or maybe even 2 or 3)... and because of such ratio they don't have any obligations to continue seeding...

but instead of disconnecting, they stay to ensure that torrent isn't dead... don't see any selfishness here

you must have misunderstood me, I didn't mean that ANY seed can work this way... only those, that have ratio >1.0