[ubuntu-uk] 3G Connection issues

Jim Price d1version at hotmail.com
Mon Apr 14 13:21:06 UTC 2014

On 04/14/2014 01:33 PM, Gareth France wrote:

>> ping -M do -s 1400 google.com
> Reducing to 1400 worked but if I wait until the pages stop loading I get
> this:
> ping: unknown host google.com

The optimum MTU setting will be a multiple of 4 lower than 1500. The way 
to find the optimum setting is to lower it until you don't get 
fragmentation then increase it until the last value before fragmentation 
sets in. This is ideally suited to a binary chop style search, so try 
increasing the test from 1400 to 1464, then either up or down by half as 
much (32) depending on whether that re-introduces fragmentation or not, 
then repeatedly up/down half as much again (16, 8, 4) until you have 
reached increments/decrements of 4. You're guaranteed to reach the 
optimum MTU in a handful of searches.


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