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

Justin Cormack justin at street-vision.com
Tue Feb 8 08:15:53 EST 2005


> 
> 
> Justin Cormack wrote:
> >>What's 'using'?
> >>Do you expect to have a storage volume that large or to transfer 
> >>torrents that large?
> > 
> > 
> > Torrents that large.
> 
> Amazing. But with size doubling every two years, it'd still be 14 years 
> until the limit is hit.

The doubling rate of data storage is often reckoned to be higher than this.
And otehr people have mroe data.
 
> >>>>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
> 
> 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.
 
> > 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.

> >>>>>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.
> 
> 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.

>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 



 
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