[bittorrent] question on the blocks downloading in BT

Simon Spero ses at unc.edu
Sat Jun 11 22:36:03 EDT 2005


Elliott Mitchell wrote:

> Not a problem, merely a minor weakness.
>
The problem is that this phenomenon interacts badly with the current 
"tit-for-tat" flow control system.  Because the transfer time for an 
entire block is greater than the interval over which bandwidth is 
measured, peers must rely on  partial blocks  when deciding whether to 
unchoke or not.

A malicious peer behind an asymmetric compressed uplink can gain an 
unfair advantage by replacing real data with chunks of very low entropy 
rubbish (e.g. all zeros, etc).



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