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Sequential torrent

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I just joined a torrent with 1 seeder and 35 peers. The available data is all at the front of the torrent:

[####################---------------------------------------]

(where # is the available data)

To me, this means that the 1 seeder is sequentially seeding the torrent, although why and how is beyond me.

But the second curious thing is that I am now getting the data sequentially. This would mean that the rest of the swarm is also providing it to me sequentially (I'm not connecting to the seeder at all). Note that I have not set my client to download this torrent sequentially.

The only other explanation I can come up with is the interface is displaying incorrect information to me, but I don't think so as the other two torrents I'm downloading are downloading non sequentially across the whole set of data as normal.

What can cause a torrent to seed this way? Is it a part of the protocol? Is the seeder doing it on purpose? Why? Is it to prevent hit and run'ers?

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Yes.

I've seen this happen before too. About half a dozen times over the years. I don't think it's at my end, I think it's something the seeder is doing. If I could connect to the seeder I could see which client they are claiming to be, but I can't do that for whatever reason. I can only assume they're blocking me. They appear to be online because every few minutes a new piece gets delivered to me via the swarm, regular as clockwork.

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I saw something like this when downloading from uTorrent super seed, I was the first and only peer. It seems that uTorrent uploads sequentially when super seed is enabled but it's not that obvious when there are more peers. So my guess is: you actually have seen super seeding uTorrent, the swarm was giving you pieces sequentially because the seed was uploading them in that order.

I read a lot of bad things about sequential downloading on this forum, it's funny that uTorrent's super seeding happens to upload in this manner ;) .

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it's funny that uTorrent's super seeding happens to upload in this manner
Not really, it's simply a function of the "Super-seed" algorithm

With only one available seeding peer, ALL available pieces are equally "rare" so the probability of being sequential is the same as the probability of being random, and if the available seed follows the super-seeding algorithm "strictly", one seed plus one peer in the swarm means it will be sequential.

Sequential downloading becomes less and less efficient as the seed/peer ratios increases, but at 1:1 it is EXACTLY as efficient as the 'rare' piece algorithm is.

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When there are a lot of seeds and a couple of peers it doesn't matter too. I think sequential downloading is a problem only if a lot of peers downloads in this way at the same time.

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