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WHY IS BEING
FIREWALLED
BAD?
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How can I be firewalled?
BitTorrent says I'm uploading.
Being firewalled
doesn't mean you can't send out data; it means other peers can't
initiate connections to you. If you initiate the connection, then
that's fine; but if the other peer is firewalled as well, it means you
two can't connect.
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Why
does this make a difference?
If you're
firewalled, it means the peers you are connected to are bearing a
heavier load than if you were not firewalled, and your download
performance will suffer.
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The graph on the
right represents a torrent with 12 peers, 6 firewalled (red) and
6 with open ports (blue). The blue peers each have connections to
11 others, and those others are dividing their uploads among an average
of about 8 other peers. The red peers each have connections to 6
others, and those others are dividing their uploads among 11 peers
each.
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This means that, in
a swarm with equal numbers of open and firewalled peers, that peers
with open ports receive 2.4 times as much attention as those whose
ports are blocked.
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Unfortunately,
there are a lot of firewalled peers out there, and your swarm may look
more like this one... In this swarm, with
ten firewalled peers
and only four with open ports, the peers with open ports get 7 times as
much attention.
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Isn't having open ports bad?
Well, you shouldn't
leave your computer without some form of security, especially if you're
running Windows. But there's a difference between leaving your
NetBIOS port 139 exposed to the world (equivalent to having a nice big
doggy door and no dog in a bad neighborhood) and opening specific ports
for particular purposes.
In the case of BitTornado, because it runs under a bytecode-interpreted
engine, it is unlikely an attacker would be able to actually take over
your machine. DoS-type exploits (which may cause BitTornado to
cease operation or crash) are potentially possible, but the
author takes some pains to try and ensure that doesn't happen.
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And so, the moral of
the story is simple: Open your ports!
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