[vox-tech] bittorrent - no seeds but distributed copies increase

[Samuel N. Merritt]

On Mon, Jul 26, 2004 at 02:08:22PM -0700, Peter Jay Salzman wrote:
> Question:
> 
> How does the "distributed copies" get larger when there are no seeds?

I think that "distributed copies" measures how many complete copies of
the file you could get if you took all the pieces that everyone has and
assembled them. 

For example, consider a five-part file.
Alice has: 1 2 3 4
Bob has:       3 4 5 
Carol has: 1 2   4 

You could make one complete copy of the file from all this, so there'd
be 1 distributed copy. If Carol got piece 5 from Bob, then you could
assemble two complete copies. 

That's the integer part of distributed copies; I'm not sure where the
fractional part comes from. Maybe it's the size of the largest
distributed incomplete subfile divided by size of file, but that's just
a shot in the dark. 
 
> Does the tracker ever inject packets into the torrent when needed (like
> when seeds == 0 and distributed copies < 1.0)?

No. The tracker doesn't have a local copy of the file. If there are no
seeds and < 1 distributed copy, everyone's download will stall before
finishing 

-- 
Samuel Merritt
OpenPGP key is at http://meat.andcheese.org/~spam/spam_at_andcheese_dot_org.asc
Information about PGP can be found at http://www.mindspring.com/~aegreene/pgp/
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