Standards (was [BitTorrent] Back to Merkle Hash Trees...)

Justin Cormack justin at street-vision.com
Tue Feb 8 08:44:48 EST 2005


> 
> 
> Justin Cormack wrote:
> >>I consider an URL easier to pass around then a (text) file.
> > 
> > 
> > A URL is a small text file. If we can make the .torrent small enough it can
> > fit in the url.
> 
> No, an URL is a small text. It's not a file.

ok, but it fulfils the same purpose. You can write it on a wall. Either
is better than a binary file like we have now.
 
> >>>problem about get_info is that peers have to carry around enough information
> >>>to recreate the info from teh torrent file (eg the filenames). The code 
> >>>implementing the peer protocol shouldnt need to know about stuff like that.
> >>
> >>It doesn't need to know. It just has to pass the info blob around.
> > 
> > 
> > It messes up the code, because you cant allocate buffers until you receive
> > it.
> 
> What's the disadvantage of the delayed buffer allocation?

You start to get have messages for example before you know what they mean
because you dont know the piece size. Even if you just connect to a peer
to get the info blob it has to send you have messages. And a bitmap that
you dont know whether it is the right length. You are going to have to
cache all this stuff and process it later.
 
> >>>eg see the THEX paper.
> >>
> >>No it doesn't. That paper says nothing about minimal transfer size.
> >>It does mention 1 kbyte as base segment size, but my 'spec' uses 1 kbyte 
> >>as base segment size too but it doesn't use it as minimal transfer size.
> >>
> > 
> > 
> > But if you cant transfer less than 32k, there is no point having the
> > segment size less than 32k. As far as I can see.
> 
> The (only) point is to make the root hash (and top of the tree) 
> independent of the chunk/piece size and to maintain compatibility with 
> other uses of merkle hashes/THEX.

But your implementation has a fixed 32k chunk so that dopesnt matter.

Being compatible with other uses, hmm, well I am not sure. Who else is
using THEX?

Justin


 
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