[p2p-hackers] Error correcting codes to prevent failurein BitTorrent like systems?

[Enzo Michelangeli]

----- Original Message ----- 
From: "Arnaud Legout" <Arnaud.Legout at sophia.inria.fr>
Sent: Monday, December 05, 2005 4:49 PM

[...]
> from my point of view this is pure myth.
> I often see such claims that bittorrent suffers from last pieces
> problem; that if there is no seed, the torrent is dead; etc.
>  From all the experiments I performed, the reality is very different.
> Rarest first does a very good job at  replicating the rarest pieces
> in a torrent, so that  the probability to have a piece that is not
> replicated at all is very low.

Sometimes particular blocks are not missing, but mangled in transit by NAT
routers too smart for their own good (and their owners', among which, at
one time, myself). See:

http://azureus.aelitis.com/wiki/index.php/NinetyNine

The existence of such routers is doubted at:

http://www.plugndial.com/draft-jennings-midcom-stun-results-02.txt

   [...]
   Some NATs were rumored to exist that looked in arbitrary packets for
   either the NATs' external IP address or for the internal host IP
   address - either in binary or dotted decimal form - and rewrote it to
   something else.  STUN could be extended to test for exactly this type
   of behavior by echoing arbitrary client data and the mapped address
   but sending the bits inverted so these evil NATs did not mess with
   them.  NATs that do this will break integrity detection on payloads.

...but I can testify that a Sercom IP706ST once in my possession did
perform such "blind payload patch" for packets sent to the DMZ host.
Needless to say, it's been demoted to paperweight :-)

Enzo