[bittorrent] Proposed Extension to Peer Protocol

Adrian Ulrich torrent at blinkenlights.ch
Sun Nov 12 10:22:27 EST 2006

> There are legit cases where these messages would prove useful in real-world
> usage. Suppose i send a peer piece 16 of a torrent, and it turns out to be
> corrupt on their end. Wouldn't it be nice if that peer sent a message back
> to me saying that the piece was corrupt?

So an evil peer could force you to do a lot of hash-checks ? yieks! 

> on it and (optionally) resend it (assuming the peer sends a new request for
> it to me).

This might help your peer but doesn't do any good to the network:

If your peer happens to send bad data it will get blacklisted/muted by
a lot of other peers anyway (= removing the 'problem' from the swarm).

What would you do after finding a corrupted chunk? BitTorrent doesn't
provide a 'i don't have anymore' message. So you'd have to disconnect
from all clients and restart with a new bitfield.

Such a thing doesn't cure the real problem: If your peer happens to have
bad data it might
 a) be an evil peer (..who'd also ignore such messages anyway)
 b) bad hardware (..so sending bad data would happen again anyway)

I don't think that the Protocol itself should deal with such specific
client-side issues.


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