[BitTorrent] Re: bt2 protocol features

Olaf van der Spek OvdSpek at LIACS.NL
Thu Jun 10 11:43:51 EDT 2004


Elliott Mitchell wrote:

>>From: Olaf van der Spek <OvdSpek at LIACS.NL>
>>Elliott Mitchell wrote:
>>
>>>>From: Olaf van der Spek <OvdSpek at LIACS.NL>
>>>>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.
>>>
>>>
>>>Really?
>>
>>You'd have to send more HAVEs and you need more hashes.
> 
> Yes, but how large is that? 8-12 additional bytes is not much additional
> data unless you're sending out *lots* of them (either a tiny block size
> or a massive number of peers).

Or both.
What's your definition of a tiny block size?
And of a massive number of peers?

>>>a client will no longer be able to get credit for uploading garbage).
>>>
>>>Next argument please.
>>>
>>>
>>>
>>>>And at such sizes, you're running into limitations of current HDDs when 
>>>>it comes to random IO, especially on high-bandwidth links.
>>>
>>>
>>>Hmm, we can already cause this by requesting random chunks of random
>>>pieces with the existing protocol. The solution of course is to request
>>>chunks that are clustered together, and possibly have a client impose a
>>>slight penalty when discontiguous chunks are requested.
>>
>>True, but that'd introduce the concept of another block size larger than 
>>chunks again.
> 
> 
> Doesn't look that way to me.
> 
> A particular implementation _may_ cause this, but it is not a

Because it's the other peer that decides on the requests, you'd have to 
think about this in advance.

> requirement. Even if it does, the protocol may already force it; and even
> if perhaps inelegant, this may end up being the simplest way to do things
> anyway.

Is this idea/the BT protocol that complex?
IMO the complexity (of a BT client) is not in the wire protocol.
> 
> 
> So I'll admit care will be needed, but care will be needed anyway. If
> some requirement makes it absolutely impossible, _then_ this will need to
> be removed. Until that time do you object to this remaining an idea to
> _try_ to put in place?
> 
No.


-- 
Olaf van der Spek
http://xccu.sf.net/


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