[bittorrent] IO bound

Alan McGovern alan.mcgovern at gmail.com
Fri Apr 13 10:52:09 EDT 2007

> But a HAVE_NOT_ANYMORE message in BitTorrent would solve this and would
> be trivial to implement. (But it would take years untill all clients
> are implementing this .. again ..)

A "have_not_anymore" message wouldn't make sense. I'd assume a client would
only advertise "having" piece if they actually have one. Therefore, once you
have a piece, you have a piece. You want the "HaveNot" so you can control
the pieces another peer can download. This is exactly what the suggest piece
message should be used for.

> This can also lead to reduced throughput, which i believe is one of the
> criticisms of the existing
> > superseeding method using bitfield/have messages.
> BT is used to transfer GB of data. Polluting the network with some
> small HAVE messages does way less harm than clients sending broken data
> or unrequested piece (this happens all the time..)

What i actually meant is not that sending all these have's slows down
throughput, it's that you will end up in a situation where Peer X would be
downloading rare pieces from you *IF* you had a full bitfield out, but
because you're doing selective sending of Have Messages, he doesn't know you
have those rare pieces therefore he won't request them off you, thus
reducing throughput.


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