[bittorrent] Re: HAVE messages

Olaf van der Spek olafvdspek at gmail.com
Wed Jun 22 19:20:30 EDT 2005


On 6/23/05, David P. Mott <dpmott at sep.com> wrote:
> Yes, you're right, this can be done.  But you still have the overhead of
> the BT protocol for each piece index.  That's all I'm saying.

But that overhead is far less significant.
 
> > If you don't update your view of the world you won't be able to
> > execute rarest first properly.
> 
> True, but so long as you can see at least one copy of each piece, I'm not
> sure that this is so important.  The whole "rarest first" algorithm is an
> arbitrary algorithm

No, it's not.

> which isn't called out in the BT spec (right?).  So
> long as you're pulling down content, I don't think it matters.

It does. To increase the chance you can complete the download.
And to increase the chance you can ask a peer for useful data (instead
of be stuck with the rarest pieces left at the end).

> >> I should also be able to gain some insight into the speed of each peer
> >
> > You should? How?
> 
> Doesn't the tracker make available the progress (uploaded and/or
> downloaded bytes) of each peer, if you ask for it?  If you monitor that,

No.

> then you can gauge the progress of your peers.
> Yes, I believe that this was also mentioned on the Yahoo mailing list.
> It's a good improvement to the current protocol, no argument.  I have no
> reason to belive that client authors are not currently doing this.

I'm afraid your belief is wrong.

> I won't argue that queueing is necessary to overcome network latency.  I
> was trying to point out that clients should reserve the right to simply
> drop requests (i.e. if they get flooded with requests or if requests
> become "stale" because it is taking too long to get to them).

In that case, a mechanism would be needed to notify the peer of the
dropped request.

> Well stated.  Specifically what about large numbers of connections do the
> TCP stack implementations have issues with?  Is it just having them
> connected, or trying to push/pull data through all of them at once?

Both, but mainly the second part.



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