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Re: Bittorrent

     On Wed, 18 Feb 2009 17:38:08 -0800 (PST) Martin Fick <mogulguy@xxxxxxxxx>
>In other words, from an anonymity standpoint, it
>seems like you would ideally want all exit nodes 
>to open up every port, even if they drastically 
>rate limit the 'evil'/abuse oriented ports?
>This way if you have to use a service on the evil 
>port, you can still do it without sacrificing
>anonymity (by being severely limited in you exit 
>node selection), but you may have to suffer a 
>very slow connection making abuse less likely.

     This is an interesting idea that merits further discussion.
>If you are really creative (and desperate,) ;) you 
>could probably already achieve port rate limiting
>by just running several exit nodes with different 
>exit policies and bandwidths.  And prioritization 
>and rate limiting could probably both be achieved 
>by adjusting the bandwith and CPU of the 
>nodes with some OS parameters, i.e. nice+20 for 
>CPU and other mechanisms for network usage.
     But this last looks to me like a really bad idea for at least two
reasons.  One is that exits are also middle relays and sometimes entry
points or even entry guards into the tor network.  Biasing the scheduling
of tor toward lower dispatch priorities affects everything that tor does,
not just exit operations.  Secondly, if tor is sharing a busy system, a
reduced priority could well lead to timeouts for many of tor's activities
that would result in additional retries and/or failures that would not
otherwise have occurred.

                                  Scott Bennett, Comm. ASMELG, CFIAG
* Internet:       bennett at cs.niu.edu                              *
* "A well regulated and disciplined militia, is at all times a good  *
* objection to the introduction of that bane of all free governments *
* -- a standing army."                                               *
*    -- Gov. John Hancock, New York Journal, 28 January 1790         *