utorrent app now supports IPv6/teredo directly

Bernhard Schmidt berni at birkenwald.de
Thu Aug 14 20:59:36 CEST 2008

Iljitsch van Beijnum wrote:

>> It now supports IPv6, along with direct Teredo support.
> Is this different from the IPv6 support in Azureus?

The most important difference is probably that while Azureus/Vuze does 
not seem to work with IPv6 on Windows at all (due to a Java bug - 
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6230761), µTorrent 
has been designed to work on Windows which is still the most dominant OS 
around. Note that I write "seem to", I did not get it to work with 
medium effort but I have been seeing Azureus peers with the typical 
Windows form of an autogenerated 6to4 address (2002:ip:addr::ip:addr) 
for at least a year now.

The other major difference is the way they find their peers when the 
tracker is not IPv6-enabled, as I expect them to be for at least one 
more year. Azureus does run a DHT (distributed hash table) on IPv6 and 
can actually find peers for popular content on an IPv6-only network, 
while µTorrent relies on PEX (PeerEXchange) to propagate IPv6 peers 
(means when µTorrent connects to a new peer it got from the Tracker or 
DHT, it asks the new peer for all its existing peers for this torrent 
and tries to connect to them). IIRC µTorrent advertises it's own IPv6 
address in PEX, which might shift traffic more easily.

And, of course, as Ross said µTorrent has a 1-click button to enable 
Teredo (actually, to my knowledge, to enable the IPv6 stack, nothing 
Teredo specific in there), so I expect this to increase the number of 
IPv6-enabled Windows XP boxes.

The amount of Teredo traffic on the relay in AS12816 has taken a steep 
and unusual rise (baseline doubled within the last 24h), but it is too 
early to be sure this is caused by µTorrent. Most of it is between 
Teredo and 6to4 anyway.


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