[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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