[BitTorrent] Re: Slave vs. free repeaters

skybuckflying skybuck2000 at hotmail.com
Sat Dec 11 08:03:20 EST 2004



--- In BitTorrent at yahoogroups.com, Elliott Mitchell <ehem at m...> wrote:
> >From: Mike Ravkine <krypt at m...>
> > First, I think this idea has potential.  The only problem I can 
see with 
> > this scenario is that the master and the slave are duplicating 
their 
> > efforts by being interested in the same pieces.  For what you 
propose to 
> > be efficient, the master should be able to split up it's 
remaining 
> > pieces and assign the correct proportion (in terms of expected 
download 
> > rate?) of them to slaves.  This way the master and the slave 
could be 
> > downloading from different peers, and acting as kind of like a 
sub-swarm 
> > inside the main swarm.
> 
> This can be solved very simply. The slave(s) look at what pieces 
they can
> get, decides on a piece that is a good one to get, and then informs 
the
> master which goes and notifies all other slaves. The picker is then
> modified to never retrieve a piece another slave (or the master) is
> attempting to get. This boils down to replacing the old scenario 
where
> the set of pieces you're interested in is the set that you don't 
have,
> with the set of pieces you're interested in is the set that the 
group
> doesn't have.
> 
> This also takes care of multiple slaves attempting to go after the 
same
> piece. In this scenario it is useful to break the master into a 
master
> portion and a slace portion. With the master handling its engine 
using
> bandwidth to upload/download as simply another slave.

Ok first let me get the idea straight ;)

I think your/this idea is something about this:

1. You have access to many machines/connections at different places, 
but those machines aren't really interested in the files. You're just 
interested in using their bandwidth.

So you suggest the use of "repeaters" to use this bandwidth.

That seems like a good idea.

2a. Then you suggest the use of slave's. These slave's might listen 
to their master and help their master get a fast download rate.

2b. A variation on this idea would be a credit system where slave's 
remember which masters they helped. The masters remember by which 
slaves they were helped etc. Then when a slave turns into master or 
vice versa the credit system will kick in and try to help them first.

I think idea's 2a and 2b are bad ideas since bittorrent and any other 
file sharing program/protocol should focus on maximum duplication... 
and not on a credit sytem or a download ratio etc... What do you mean 
with download ration 1:1 ? If somebody let's bittorrent run for a 
while after downloading etc... the ratio will go to 1:1 and later to 
1.5:1 2:1 3:1 etc... as long as it let's it run.

The point is that your master has a very low upload speed. So if all 
the slaves are sending 500 Kbyte/sec to your master... your master 
can only return 40 KByte/sec to the network.. so that's very 
inefficient ;)

Ofcourse when everybody is already done that s no problem.

But your slaves would be much smarter if they for example uploaded 
each to a 1 MB connection. That 1 MB connection has more duplication 
power :D

So in the end your master will still get 500 Kbyte/sec... but the 
difference is that it will now get it from the 1 MB connection AND 
the 1 MB connection(s) are now also seeding others ;) :D

Bye,
  Skybuck.







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