Subject: Re: More on bittorrent

From: Nathan Ward <[email-masked]>
Date: Fri, 1 Feb 2008 23:19:05 +1300

ohOn 1/02/2008, at 7:39 AM, Fred Baker wrote:

> very interesting. So I gather that you didn't have to modify BT to  
> make it use IPv6 directly, you simply used it. That's interesting if  
> only because it suggests an obvious generator for IPv6 traffic.
>
> Does it appear to prefer one or the other, or simply try both? Do  
> you have to do something specific to trigger IPv6 usage?

The original BT client<->tracker protocol itself doesn't support IPv6,  
but the Azureus and uTorrent DHT extensions do.

There is also an extension to the client<->tracker protocol to allow  
IPv6 [1]. Jeroen runs an IPv6-only tracker.
Something interesting to note, the example addresses they use on the  
IPv6 tracker extensions page[1] are Teredo addresses..

I'm using the DHT stuff, as I'm not downloading any torrents. I think  
it gets me a much much wider range of hosts to talk to.

When you refer to either or both, do you mean 6to4/Teredo, or do you  
mean IPv6/IPv4 As I mention I am only advertising a 6to4 address with  
DHT. Not sure why yet, the client doesn't seem to want to pick up more  
than one address. I have significantly fewer Teredo clients than I do  
6to4 clients. I assume that's because I am advertising a 6to4 address.

Some interesting errors from the client:
[net] PRUDPPacketHandler: send to /2002:c0a8:140:1:0:0:0:1:35104  
failed: Network is unreachable
[net] PRUDPPacketHandler: send to /2002:a00:1:1:0:0:0:1:14544 failed:  
Network is unreachable
(RFC1918 based 6to4 addresses)

I also note that those addresses are not in the standard windows 6to4  
address format. Windows normally does:
2002:AABB:CCDD::AABB:CCDD, so the IPv4 address is duplicated, so those  
addresses must be from misconfigured Linux or BSD machines that maybe  
have automatic "bring up 6to4 when this interface has an IPv4 address"  
features.

Numbers:
- Unique inbound sources on 6to4: 20549
- Unique outbound destinations on 6to4: 45882
- Unique inbound source on IPv4: 115307
- Unique outbound destinations on IPv6: 169391

The ratio of inbound:outbound is better on IPv4 it seems, but I'm  
unclear if that is because more hosts are responding to my requests,  
or if there are more hosts that are probing on IPv4. I'm inclined to  
expect it to be the latter..
I'm hacking some code together now to give me an idea of how many  
hosts reply to my probes.

Cheers,

--
Nathan Ward

[1] http://www.bittorrent.org/ipv6_tracker_extension.html