Seeds and downloader free-riding problem in BT.

[dream2skyline]

Hi,there:
Excuse me if I send this message twice.
I have several question considering seeds and downloader here. Seeds
only upload files pieces to other peers because it has the whole copy
of file and downloader(leechers) download what they need and upload
what they have because they only have partial copy of whole file.
Is there any other difference between seeds and downloaders?
We are considering the free-riding part of bittorrent. How could
seeds decide which peer to upload(unchoke) because no peer have a
download rate to the seeds? In contrast downloader (peer A) will
unchoke the fifth peer depending on the downloading rate to Peer A
every 30 seconds.
Does the tracker site discriminate the seeds and downloader? What
kind of strategy for the seeds to decide which peer to upload to? If
there any queue of seeds used for the peers to wait until to be
served by seeds? As we know it is not necessary for other peers to
download sth to the seeds and it seemed that it is good idea for the
free-rider to take advantage of that fact and they prefer to be
served by the seeds and wait in that kind of queue( If they can
select other peer to download). If the free-rider is denied by other
peers continusly (they have 20% chance to be served of course), most
of free-rider will like to turn to seeds to continue their free-
riding because the success chance is larger than 20%. Am I right?

Best
DY






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[Vitenka]

Post by dream2skyline
Is there any other difference between seeds and downloaders?

No. A seed is just a peer who happens to have a full copy of the file(s).

However some clients use slightly different logic when deciding which
peers to send to whilst seeding than while downloading.

Post by dream2skyline
We are considering the free-riding part of bittorrent. How could
seeds decide which peer to upload(unchoke) because no peer have a
download rate to the seeds? In contrast downloader (peer A) will
unchoke the fifth peer depending on the downloading rate to Peer A
every 30 seconds.

Seeds optimistically unchoke random peers. They CAN choose to do more
(eg. send out pieces which are rare in the swarm, or send to peers with
few pieces)

Post by dream2skyline
Does the tracker site discriminate the seeds and downloader?

Yes, but only for stats purposes.

Post by dream2skyline
What kind of strategy for the seeds to decide which peer to upload to?

By default, random selection amongst all peers the tracker has told you
about.

Post by dream2skyline
As we know it is not necessary for other peers to
download sth to the seeds and it seemed that it is good idea for the
free-rider to take advantage of that fact and they prefer to be
served by the seeds and wait in that kind of queue( If they can
select other peer to download). If the free-rider is denied by other
peers continusly (they have 20% chance to be served of course), most
of free-rider will like to turn to seeds to continue their free-
riding because the success chance is larger than 20%. Am I right?

Yes - if you do not upload then you will (in the limit) only be able to
download from seeds. There are usually less seeds than normal peers -
so a 'free rider' will get a slower download rate than a normal peer.



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