OSX network errors

4 09 2008

OSX has a bug in its network stack, apparently associated with a 10.5 update, but it appears to fix slow performance on large file transfers on Tiger as well. Details are http://gp.darkproductions.com/2008/03/fix-for-slow-wifi-80211-file-transfers.html here. 

The main issue is the ack response, where both machines back of and wait for the other to ack, being far to polite. It appears to have fixed things for me backing up on a very very slow time capsule, which is not fast again.

The commands to reduce the ack are 

sysctl -w net.inet.tcp.delayed_ack=0

and to set it back to defailt 

sysctl -w net.inet.tcp.delayed_ack=3

and to list it

sysctl net.inet.tcp.delayed_ack

The annoying part is, if the a network mounted disk is mounted over a dodgy tcp connection, it will loose the mount and stall other disk activities. This can turn up as slow response, rather than total loss of the mount.




3 responses

10 09 2008
Ian Boston

And to make this permanent,
echo net.inet.tcp.delayed_ack=0 >> /etc/sysctl.conf

11 11 2008

I whant to set it permanently.
After typing in terminal

echo net.inet.tcp.delayed_ack=0 >> /etc/sysctl.conf


sudo echo net.inet.tcp.delayed_ack=0 >> /etc/sysctl.conf

I’m getting ‘Permission denied’ error, what do I do wrong?

11 11 2008
Ian Boston

/etc/sysctl.conf is probably not writable by you for some reason, try editing in vi

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