[BitTorrent] Re: bt2 protocol features

Olaf van der Spek OvdSpek at LIACS.NL
Mon Jun 7 12:10:51 EDT 2004


dpmott at sep.com wrote:
> --- In BitTorrent at yahoogroups.com, Bram Cohen <bram at b...> wrote:
> 
> 
>>>Related thing, how about peers refering to pieces *strictly* by 
>>>hash?
>>
>>It turns out that the size of those hashes can be fairly 
>>significant, and the program logic winds up doing a lookup to 
>>translate back from hash to index on the other side anyway.
> 
> 
> Let me know if any of this is wrong...
> 
> If you were to eliminate the "offset" and "length" fields when 
> requesting a chunk, and make the chunksize appropriately small, then 
> you could just request a chunk by offset.
> 
> And, you can request a validation hash for each chunk.
> 
> And, this approach would elminate that whole "chunk" and "piece" 
> distinction...
> 
> Is any of that wrong, or undesirable for some reason?

Yes, a piece size of between 16 kb and 64 kb would be required and that 
would significantly increase the protocol overhead compared with 2 mb 
pieces.
And at such sizes, you're running into limitations of current HDDs when 
it comes to random IO, especially on high-bandwidth links.


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