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To: cs551@merlot.usc.edu
Subject: Re: End-game mode for BitTorrent 
Date: Sat, 28 Apr 2007 08:13:07 -0700
From: william@bourbon.usc.edu

Someone wrote:

  > Does "based on the uploading rate" here imply that
  > the leeches with lower downstream traffic will
  > be favored by seeder?

Normally, whom to unchoke depends on the "download rate"
of peers.  When a node becomes a seeder, no peer will be
downloading to it.  So, looking at downloadingn rate is
useless.

At this point, looking at "uploading rate" makes sense
because for a seeder, it is good to get its data out as fast
as possible.  So, the higher the peer's upload rate the
better.  Therefore, the policy is to unchoke peers with the
highest upload rates.  (I guess an alternative is to contact
the tracker and see which piece is the rarest in the torrent
and use that as a priority to decide which peer to upload to.
But this requires contactingn the tracker and that's not
desirable.)
--
Bill Cheng // bill.cheng@usc.edu <URL:http://merlot.usc.edu/william/usc/>





  On 4/27/07, william@bourbon.usc.edu <william@bourbon.usc.edu> wrote:
  > Someone wrote:
  >
  >   > On p. 29 of lecture 20, it reads that seeders will
  >   > unchoke peers "based on the uploading rate", then
  >   > "preferring peers which no one else happens to be
  >   > uploading to them at the moment".
  >   >
  >   > Are the two statements counter to each other?
  >
  > I don't think so...  I think the way to interpret the
  > last bullet is:
  >
  >     as a result, this would prefer peers which no one else
  >     happens to be uploading to them at that moment
  >
  > Does this make more sense now?