DHT using excessive connections.

[Nutty]

Hi.

My flat mate is using uTorrent 1.5, and I noticed everytime he has it running, our broadband takes a beating.

My router shows the number of active nat sessions going on, and I noticed he was using about 1,300 connections.

His uTorrent settings are set to use a maximum of 500 connections globally. Using TCPView however showed lots and lots of connections using the non data exchange port. We tracked this down to the DHT option in uTorrent.

With DHT off, total network nat sessions were around 500.. Enabling DHT, this rocketed up to over 1,200 in less than 2 minutes.. I think DHT connections should obey the global connection limit, or perhaps uTorrent isn't closing the connections properly so they linger for ages until they timeout by the router.

[Ultima]

UDP is connectionless. Meaning it's just a packet. That's all, it's not a continuous back-and-forth communication like TCP is, so it can't be counted, and as such, it can't be limited.

[Nutty]

Well my router still gets clogged up with it, and once it hits the conneciton limit, it screws browsing up.

[Ultima]

I know, some routers can't handle the number of UDP packets, mine included. The only thing you can do is disable DHT or get a new router. IIRC, µTorrent's DHT implementation uses more UDP packets than other clients'. Might have something to do with the fact that ludde reversed engineered the protocol, since there wasn't enough documentation on it.

[Nutty]

I'm not getting a new router I just bought it.. Can handle 1,500 connection which was about 3 times more than my previous one.. Still, azureus distributed networking doesn't cause the same issue, which is what I use.

[Ultima]

Indeed, like I said, the DHT implementation in µTorrent is probably more UDP packet intensive than other clients. In any case, unless you're always on dead or near-dead torrents, there is no point in having DHT enabled anyway.

[Firon]

UDP = connectionless. (despite what your router might think)

UDP = problematic for a lot of (cheap) consumer hardware.

Solution, turn off DHT, or get a better router.

[Nutty]

My router is good enough thanks

I've just turned his DHT off.. Just thought I'd bring it to ppl's attention.

[Firon]

Not good enough, since it can't handle DHT.

[Nutty]

It can handle DHT in azureus just fine.

[Firon]

So? Azureus' DHT is very different from Mainline's. And my router can handle both of them, even at the same time, so yours isn't that good. It's choking on a pretty low amount of UDP packets.

[Nutty]

What router you got ?

[Firon]

Linksys WRT54G

[Nutty]

Meh.. I prefer mine.