Network end users to pull down 2 gigabytes a day, continuously?

Stephen Sprunk stephen at
Sun Jan 21 19:07:22 UTC 2007

Thus spake "Joe Abley" <jabley at>
> If there was a big fast server in every ISP with a monstrous pile of 
> disk which retrieved torrents automatically from a selection of 
> popular RSS feeds, which kept seeding torrents for as long as there 
> was interest and/or disk, and which had some rate shaping installed 
> on the host such that traffic that wasn't on-net (e.g. to/from 
> customers) or free (e.g. to/from peers) was rate-crippled, how far 
> would that go to emulating this behaviour with existing live 
> torrents?

Every torrent indexing site I'm aware of has RSS feeds for newly-added 
torrents, categorized many different ways.  Any ISP that wanted to set 
up such a service could do so _today_ with _existing_ tools.  All that's 
missing is the budget and a go-ahead from the lawyers.

> Speaking from a technical perspective only, and ignoring the legal
> minefield.

Aside from that, Mrs. Lincoln, how was the play?

> If anybody has tried this, I'd be interested to hear whether on-net 
> clients actually take advantage of the local monster seed, or whether 
> they persist in pulling data from elsewhere.

Clients pull data from everywhere that'll send it to them.  The 
important thing is what percentage of the bits come from where.  If I 
can reach local peers at 90kB/s and remote peers at 10kB/s, then local 
peers will end up accounting for 90% of the bits I download. 
Unfortunately, due to asymmetric connections, rate limiting, etc. it 
frequently turns out that remote peers perform better than local ones in 
today's consumer networks.

Uploading doesn't work exactly the same way, but it's similar.  During 
the leeching phase, clients will upload to a handful of peers that they 
get the best download rates from.  However, the "optimistic unchoke" 
algorithm will lead to some bits heading off to poorer-performing peers. 
During the seeding phase, clients will upload to a handful of peers that 
they get the best _upload_ rates to, plus a few bits off to "optimistic 
unchoke" peers.

Do I have hard data?  No.  Is there any reason to think real-world 
behavior doesn't match theory?  No.  I frequently stare at the "Peer" 
stats window on my BT client and it's doing exactly what Bram's original 
paper says it should be doing.  That I get better transfer rates with 
people in Malaysia and Poland than with my next-door neighbor is the 
ISPs' fault, not Bram's.


Stephen Sprunk         "God does not play dice."  --Albert Einstein
CCIE #3723         "God is an inveterate gambler, and He throws the
K5SSS        dice at every possible opportunity." --Stephen Hawking 

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