[bittorrent] a question on Random First Piece

Justin Cormack justin at street-vision.com
Thu Jun 9 09:00:59 EDT 2005


On 9 Jun 2005, at 13:38, Tom H. Lan wrote:

> Dear everyone,
>
> I have a question puzzle me a lot and I need your help.
>
> You see in BT that each file is chopped into different blocks and  
> then further chopped into pieces. Peers relay the blocks between  
> each other. I wonder whether block is the unit of the request. I  
> mean that whether it is possible that peers will relay the block  
> they are downloading which may have not been totally downloaded. If  
> yes, it seems to me that the conception of block is useless.
>
> And we know that a new peer who joins the BT networks will random  
> choose a block to download. Does it mean that it can only upload to  
> others when it finishes downloading the block.

Yes thats right, peers will only request a block when the other peer  
sends a 'have' message, which will only be when the whole block has  
been downloaded and verified, so there will not be requests for  
unverified parts.

Justin




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