[bittorrent] Choice of listener ports

larytet.8708132 at bloglines.com larytet.8708132 at bloglines.com
Sun Mar 27 17:57:55 EST 2005


--- Simon Spero <ses at unc.edu wrote:
Kenneth Porter wrote:
> 
> > [Porter
proposes circumventing local firewalls by using ports outside 
> > the 6881-6889
range]
> >
> > What problems would you foresee from doing this?
> 
> The
first problem is that bittorrent connections can easily be 
> identified
by examining the first 48 bytes transmitted by the session 
> initiator.
  The first 28 bytes tell you it's  bittorrent; the next 20 
> bytes identify
the torrent.
> 
> The second problem is that bittorrent has a rather distinctive
traffic 
> pattern; even if connections are encrypted,  it's pretty obvious
what's 
> going on.  Any actions to disguise these traffic patterns will
severely 
> impact thruput.  It's also  hard to disguise the sheer volume
of traffic 
> associated with a busy torrent.
> 
> The final problem is
that listen ports are chosen by individual clients; 
> although the user
can chose his own advertised listen port, unless all 
> other members of
the swarm use that port,  this move is futile.  I 
> believe there are some
trackers that enforce non-standard listen ports 
> for precisely this reason.

> 
> Simon

sorry for double email - bloglines mailer is not created for
sending emails.

one could fake RTP packets and encrypt payload. encryption
key can be made part of torrent file. 

BT is sensitive to statistical analys,
but this can be corrected to some degree if choose larger blocks and make
some changes in the protocol.

There are more than one P2P networks where
peers exchange with dummy encrypted packets to hide packets containing real
data.




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