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

Olaf van der Spek OvdSpek at LIACS.NL
Tue Feb 8 06:22:18 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?

>>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.

>>>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)?


 
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