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I'm running 10.10 on a desktop and I have two routers: the first connects to the Internet and serves DHCP addresses to my devices, the second is a WiFi LAN around the house. Both routers run Tomato firmware.

My issue is whenever I play music on my desktop (using MPD/ncmpcpp) or a video (either Totem or VLC) conky reports my upload speed at around 200Kb/s and my WiFi LAN goes down. As soon as I stop MPD or VLC the network comes back up.

How would I go about troubleshooting this?

Edit: interestingly enough, the LAN stays up when I use Skype

Edit 2: after following ijk's suggestion, wireshark show that port 46560 is being flooded. lsof shows that it is pulseaudio:

pulseaudi 2190 jason 39u IPv4 14110 0t0 UDP mybox:56751->224.0.0.56:46560

Seems it is a bug: https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/411688

Update The solution, from an admittedly sketchy memory, is to install and open the pulse audio control settings and disable netwrok broadcasting--this will stop pulse flooding your network.

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The fix is to install paprefs and to disable Multicast/RTP –  user18838 Jun 5 '11 at 23:03
    
Congratulations of solving your issue. So that this question and answer can be useful for others who have the same issue, maybe you should add the solution and mark it as accepted. –  Stephen Myall Aug 17 '12 at 20:22
1  
I no longer use Ubuntu (and this bug was one of the reasons why I gave up on it), but I'll update my question with what I vaguely remember as the fix for the bug... –  user18838 Aug 17 '12 at 22:18

4 Answers 4

The OP found the solution.

From a comment:

The fix is to install paprefs and to disable Multicast/RTP

From an edit to the question:

The solution, from an admittedly sketchy memory, is to install and open the pulse audio control settings and disable netwrok broadcasting--this will stop pulse flooding your network.

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I've experienced similar issues with 3rd party router firmware on some devices. The problem was simply that the devices would get bogged down by the heavy transfer, some sort of buffer overflow would occur, and the device would panic or reboot. Not to say that this is explicitly a 3rd party firmware problem, but checking that your router is actually capable of handling that kind of throughput may be where to start.

I personally changed routers a few months ago from a similar issue (while not specifically for media streaming I chose the WHR-G301N, running 3rd party firmware on it) and currently have no issues. Routers are cheap, perhaps purchasing a better router and replacing your two-router setup with one good router would be worth the price if it saves you time and future headaches. Since you have Tomato on the other routers already you could use them as mini-servers or something, so they wouldn't "go to waste".

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Thanks Kagetsuki: I have tried with two different routers (an Asus RT-N16 and a trusty WRT54GL) and it happens with both. I think it is something to do with data flooding the loopback device - but I don't know why... –  user18838 May 29 '11 at 4:40

You might try reducing the transmission queue length on the interfaces in the middle of the "chain"- that is, the Tomato router's ethernet and wifi interfaces.

The relevant command is similar to:

ip link set eth0 txqueuelen 64

where you replace 'eth0' with the interface name and '64' with the desired queue length in packets.

This is to prevent bufferbloat, which can impact network performance similarly to the problems you are encountering. You may or may not be experiencing bufferbloat, but reducing your TX queue length will not hurt anything and it can be easily set back to the original value (default is 1000).

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Thanks koanhead: I tried settings at 64, 50 and 0 - to no avail. It got me thinking about QoS, so I tried playing with different settings there. Again, no luck. I fail to understand why a local service (MPD or VLC) floods my uplink connection... –  user18838 Jun 1 '11 at 7:34

Run wireshark and see what the traffic actually is.

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Thanks ijk - that was a helpful suggestion. I've updated my question with the details. –  user18838 Jun 5 '11 at 22:42
    
While you only pointed me at the answer, I'm still giving you the bounty because your suggestion did lead to me solving the problem. Thank you. –  user18838 Jun 5 '11 at 23:04

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