P2P agents for software distribution - saving the WAN from meltdown?!?

Joe Abley jabley at ca.afilias.info
Wed Jun 18 09:52:38 CDT 2008


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




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