[bittorrent] New P2P protocols

larytet.8708132 at bloglines.com larytet.8708132 at bloglines.com
Fri Mar 25 22:15:58 EST 2005


"Using this, seeds can continually churn out new
encoded blocks, while peers
redistribute the ones they already have,
resulting in a situation where nearly
every peer has something useful
to exchange with any other peer, and eliminating
any need for
rarest-first distribution."

my understanding of these algorithms
is very limited, but as i see it you need one of two (or more) chunks to recreate
any block. i do not understand how it can eliminate ANY need for rarest-first
distribution.


"Proximity-based connections. While BT does a reasonable
job of picking
good peers to download from and upload to, it's far from ideal"


Another interestin outcome of this is relatively more secure network


>From http://larytet.sourceforge.net/posts.php

....imagine regular torrent
with swarm 10,000+ peers. If average number of connections is 50 the probability
for a IP address to be logged by adversary is 0.5% or 1:200. The easiest path
to anonymity in existing BT networks is scale. Or one can say that BT is not
secure BECAUSE it is NOT popular enough. One can also argue that BT is not
centralized enough. Instead of only one torrent file with latest TV show there
are 3 or 4 running simultaneously in different formats, codecs, on different
trackers. If BT network breaks 50 mil users my wild guess that most popular
items will be relatively secure. BT tracker can divide the swarm into groups
with 50-100 participants. When a new peer arrives tracker can join the peer
to already existing group or create new group and move some seeds/leachers
from the existing groups. Chance that adversary will connect/see IP addresses
belong to more than one group are


n/G

where n is a number of IP different
addresses belong to adversary and G is a number of groups The chance for any
peer to be logged is the same. Tracker can make intelligent guess based on
the subnet that multiple IP addresses belong actually to the same peer and
move addresses to the same group while removing not related IP addresses.
Interesting side effect of this would be that geographically close peers (sitting
behind same DHCP server) would find each other in the same group. All this
is relevant only for large swarms on the order of number of available ports/connections
on the regular desktop. We are talking about 10-50K participants. RSS feeds
containing links to torrent files and automatic download tools based on these
feeds can create such swarm.



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