Torrent clients kill OS X network stack

[funkahdafi]

Hi,

what I describe here has been an issue for many years and throughout many OS X versions (I think I started seeing this in 10.6).

What happens? Downloading torrents, especially ones that contains more than 5-6 files, tend to completely kill the network stack on my Mac. It is NOT killing the internet connection, it's not an internet issue. It's killing all network conenctions locally on the machine. How do I know? Because I am not only loosing internet connectivity, I am also loosing connectivity to all LAN ressources (NAS, for example). It’s as if the network stack freezes.

I might add: When I say it's killing all connections to local (LAN) ressources, you should know that these ressources are not connected to the same router, so it's not the router that's being overloaded or something like that. My devices are all connected to a professional, 24 port gigabit switch (HP ProCurve), and while the Mac has the issue, the other devices on the network can still commuicate with each other. The issue is definitely isolated to the Mac itself.

The issue usually resolves after a couple of minutes, but it always comes back.

Strange thing is, this happens with most torrent clients I tried (namely Transmission and Vuze/Azureus), but it is not happening when using uTorrent.

Has anyone else experienced something like that and was able to solve the issue?

Thanks

 

[fhall1]

I've been using Transmission for years (I'm on OS X 10.8.5 now)...however, I have remained at Transmission version 2.11 because it's the last version to support a proxy. I've never experienced what you're describing.

 

[BrianBaughn]

I assume the switch is connected to the same router (for DHCP). The traffic through a good switch to another device on that switch doesn't necessarily have to go through the router. An example would be gigabit links between gigabit devices on a gigabit switch working although the router may not be gigabit capable.

My guess is that the number of connections is overloading the router, depending on what software you're using.

 

[funkahdafi]

I assume the switch is connected to the same router (for DHCP). The traffic through a good switch to another device on that switch doesn't necessarily have to go through the router. An example would be gigabit links between gigabit devices on a gigabit switch working although the router may not be gigabit capable.

My guess is that the number of connections is overloading the router, depending on what software you're using.

That's what I was saying in my opening post: All the devices are connected to the switch, NOT the router. The router is not the issue. The router is not overloaded.

Again: The only device on the network loosing connectivity is the Mac itself. All other devices continue to operate fine and can access the internet without issues while at the same time the Mac is completely borked. It is clearly an issue on the Mac, not on the network.

 

[thepawn]

So this is old, and I'm bubbling it up, but I still to this day have this same problem. I've scoured the internet and can't see any fixes for it, just lots of random scattered discussions. It seems to be an "mbuff starvation" issue in the network stack. While I'm running torrent, the only thing I can do to keep things alive is a while look in a Terminal shell that ifconfig restarts the network stack every 120seconds. Anyone ever figure out what to tune to get this starvation issue to not happen?

 

[chrfr]

So this is old, and I'm bubbling it up, but I still to this day have this same problem. I've scoured the internet and can't see any fixes for it, just lots of random scattered discussions. It seems to be an "mbuff starvation" issue in the network stack. While I'm running torrent, the only thing I can do to keep things alive is a while look in a Terminal shell that ifconfig restarts the network stack every 120seconds. Anyone ever figure out what to tune to get this starvation issue to not happen?

Just make sure that your uploads aren't saturating your internet connection. It's worthwhile to set a cap a bit below the potential maximum speed.

 

[thepawn]

My uploads are always throttled, it's not that. I limit to 1920KB/s , or ~15Mbs and I'm on a 1Gbs connection (with 2Gbs trunk to my core). It's a buffer saturation issue somewhere for coming connections. I've been playing with sysctl values. Testing a new set:
kern.ipc.maxsockbuf=4194304
kern.ipc.somaxconn=2048
kern.ipc.nmbclusters=2048
net.inet.tcp.rfc1323=1
net.inet.tcp.win_scale_factor=4
net.inet.tcp.sockthreshold=16
net.inet.tcp.sendspace=1042560
net.inet.tcp.recvspace=1042560
net.inet.tcp.mssdflt=1448
net.inet.tcp.v6mssdflt=1440
net.inet.tcp.msl=15000
net.inet.tcp.always_keepalive=0
net.inet.tcp.delayed_ack=3
net.inet.tcp.slowstart_flightsize=20
net.inet.tcp.local_slowstart_flightsize=20
net.inet.tcp.blackhole=2
net.inet.udp.blackhole=1
net.inet.icmp.icmplim=50