On 18 Jun 2008, at 10:42, Adrian Chadd wrote:
<random type="idea from tonight">
If only there was a way for a SP to run a BitTorrent type service for
their clients, subscribing the BT server(s) to known-good (ie, not
warez-y)
torrents pre-seeded from trusted sources and then leaving it the hell
alone and not having to continuously dump specific torrent files into
it.
</random>
Automatically leeching and then seeding for long periods is trivial to
set up if you can get an RSS feed with torrent enclosures. It is my
(highly theoretical, naturally) understanding that many BitTorrent
trackers make such feeds available.
However just because you have a fast, on-net seed for particular
torrents doesn't mean that your on-net leechers will necessarily pick
it up. The behaviour I have observed with BitTorrent is that clients
are handed a relatively short list of potential peers by the tracker,
and it's quite common for sensible, close, local peers not to be
included. My assumption has been that the set of potential peers
passed to the client is assembled randomly.
If this behaviour is widespread (i.e. if my observations are valid and
my interpretation of those observations reasonable) then the more
popular the content, the less likely leechers are to see the seed you
want them to see. This relegates your local, on-net, fast seed to be a
way of distributing unpopular content (that which is not being seeded
by many other people).
There has been at least one presentation at NANOG in the past couple
of years which describes the benefit to ISPs of p2p, by virtue of
keeping traffic for popular content on-net. From memory, however, that
presentation was based on a non-deployed p2p protocol which made more
of an effort to help peers find local peers than the clients I
described above.
Joe
