Re: [Help-gnunet] INDIRECTION_TABLE_SIZE and download speed

[Christian Grothoff]

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On Friday 06 September 2002 01:11 pm, Tracy R Reed wrote:
> > Well, you don't know what bandwidth the other side had, do you? How much
> > of your bandwidth was used at that time? (and did you run 0.4.6c?).
>
> The other side must have been using a 9600 baud modem because it was
> pathetic. :) And I was trying to download around 8 files. Only 5 ever
> actually started receiving data after a couple of hours and those five
> only received a hundred k or so each. Odds are the files were coming from
> different places so they should not have all been incredibly slow.
>
> Practically none of my bandwidth was used at the time. I am using 0.4.6c.

So probably the files were not available (or only fragments were, or they were 
on a node that went offline (or on- and offline)), this is p2p, so it's 
possible that the other side is not available. And since it's anonymous p2p, 
you can't just "test" if the other side is available since you're not 
supposed to be able to tell who it is. 

> Also, I notice that as soon as I start a download a file is created with
> the proper size. I assume it is then filled in with the data as it
> arrives. What is the reason for this? At first I thought WOW this is fast!
> But when I inspected the file contents it was all nulls. Then hours later
> I still hadn't received even half of the file.

The reason is, that we get the blocks in random order. The code also checks if 
we already have an idenitical file on the drive, and if yes, these pieces are 
not downloaded again. Since the pre-existing file may be longer than the new 
file, the first thing we do is truncate (or lengthen) it to the "right" size. 
This is what you observed.

Christian
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