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

Justin Cormack justin at street-vision.com
Tue Feb 8 06:30:36 EST 2005


> 
> 
> Justin Cormack wrote:
> >>
> >>Justin Cormack wrote:
> >>
> >>>>Justin Cormack wrote:
> >>>>
> >>>>
> >>>>>>>32 bits for the piece. I thought everyone had pretty much agreed that 1k/4k
> >>>>>>
> >>>>>>2^47 bytes doesn't look like a 'big' limitation.
> >>>>>
> >>>>>
> >>>>>Its a bit too small, 128TB, as it is within range of the size of filesystems
> >>>>>people have now, let alone a few years in the future.
> >>>>
> >>>>Let's just say I'd love to hit that limitation.
> >>>
> >>>
> >>>Better safe than sorry.
> >>
> >>The largest torrents I've seen were about 8 gb. That's a factor 16384 
> >>smaller then the limit. I doubt the protocol will still be in use when 
> >>this becomes an issue.
> > 
> > 
> > I am expecting to be using 1TB+ by the end of this year, so it seems a lot
> > closer...
> 
> What's 'using'?
> Do you expect to have a storage volume that large or to transfer 
> torrents that large?

Torrents that large.
 
> >>But those root hashes are in the info key.
> > 
> > 
> > Are we talking at cross purposes? I thought the idea was a URL that would
> > replace the torrent file by encoding all the information in it.
> 
> No, it's only supposed to contain the info needed to join a torrent.
> The rest of the info key would be retrieved via the get_info/info extension.

Ah I see.

I still think that (as per my original post at the start of the thread)
having a text based torrent file is a better solution than this. The main
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.
 
> >>>Most of the time it makes sense to do transfers in large amounts at a time
> >>>it is just at the beginning you might want a lower value.
> >>
> >>True.
> >>
> >>With 4k chunks, do you keep the entire merkle tree in memory?
> >>
> > 
> > 
> > If you dont want to use this much memory, you can choose a large chunk size
> > yourself, never request less than that  and never use the small hashes (though
> > I suppose you might have to calculate them if requested which is a 
> > disadvantage).
> 
> Could you post the URL of the post with the reasons why 4k was chosen 
> (or repost the reasons themselves)?
> 

eg see the THEX paper.
 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 



 
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