[BitTorrent] Seeds and downloader free-riding problem in BT.
vitenka at ntlworld.com
Wed Mar 9 13:07:52 EST 2005
> 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.
> 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
> Does the tracker site discriminate the seeds and downloader?
Yes, but only for stats purposes.
> 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
> 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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