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

Olaf van der Spek OvdSpek at LIACS.NL
Tue Feb 8 08:07:51 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.

>>>>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.

> 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.

>>>>>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.


 
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