[BitTorrent] Re: Request for protocol extension: get_info/info messages

Olaf van der Spek OvdSpek at LIACS.NL
Wed Jan 12 14:37:00 EST 2005

> --- In BitTorrent at yahoogroups.com, Elliott Mitchell <ehem at m...> wrote:
>> >From: iain_wade <iwade at o...>
>> > The intention of our caching peer is to have it passively
>> > listening for connections solely from our own customer base,
>> > not to participate in the general torrent distribution.
>> >
>> > To be able to do this, we need two things. The first is to get
>> > the clients to connect to us. We need that to happen by default
>> > as relying on user configuration would limit this feature to
>> > a small fraction of the user base. (I have a http proxy (for
>> > tracker communications) written which will add itself to the
>> > list of peers before returning, but getting a few hundred
>> > thousand people to change their settings is going to be a
>> > problem for us).
>> Why not replace the returned list with *just* your cache?
>> The simplest approach might be to return one IP:port pair for
>> each peer the tracker returns. By then imitating the client
>> actions, you can reasonably effectively imitate how the client
>> is acting and correctly tit for tat each peer. Add in one extra
>> record that is purely the cache to provide cached blocks
>> (prevents a peer from getting over-credited).
> Because that would require proxying all communications to the outside
> world, which causes a number of problems (and helps out with a few
> others).
> It also significantly complicates the code required.
> Think performance and scalability.
> We have significantly more broadband customers than the 64k available
> ports, let alone multiplying that by the number of peers they are
> talking to.

You only need a single port. Only the tuple source IP address, port, 
destination IP address, port has to be unique. 

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