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

Nathan Ward nanog at daork.net
Wed Jun 18 15:29:36 UTC 2008

On 19/06/2008, at 2:52 AM, Joe Abley wrote:
> 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.

There was a product around that would keep track of torrents and fudge  
the tracker responses to direct you to on-net peers where possible.  
Not sure what it's called. Inline box thing, much like Sandvine,  
Allot, etc. I imagine you could either inject the details of a local  
seed you're running, or keep track of on-net users and inject those.

 From a tracker software point of view, it would be fairly trivial to  
weight peer lists to prefer peers within the same ASN I imagine.
Perhaps that could be turned in to same country, or what not. Better,  
combine it with some kind of rough AS adjacency graph and <insert  
algorithm here> and viola.
Is there any data available that would let that happen easily?  
Obviously routing tables for the ASN/IP mapping, but what about rough  
ASN adjacency? It doesn't really need to be updated that often - even  
CAIDA's yearly data that they use to make their pretty pictures could  
work OK.

Seems like win/win/win - linux distribution vendors can pride  
themselves on how much faster their torrents run, end users get better  
speeds for their torrents, networks move less traffic off-net.

.. this is the part where someone bustles off and makes it go.

Nathan Ward

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