Emulating a cellular interface

Adrian Chadd adrian at creative.net.au
Sat Nov 6 20:06:48 CDT 2010


On Sat, Nov 06, 2010, Andy Davidson wrote:

> Not withstanding Mikael's comments that it shouldn't be lossy, at times when you want to simulate lossy (and jittery, and shaped, and ....) conditions, the best way I have found to do this is FreeBSD's dummynet :
> 
> http://www.freebsd.org/cgi/man.cgi?query=ipfw&sektion=8#TRAFFIC_SHAPER_(DUMMYNET)_CONFIGURATION

And cellular networks are bursty, depending upon (from what I can gather)
how busy the cell is and how many people are currently doing data.
Someone more cellular-oriented should drop in their 2c.

So to be completely accurate, you may way to script some per-node shaping
rules that watch traffic flow and adjust the rules to emulate this.
I recall seeing a few apps that behaved poorly when their UDP data
exchange timed out because my 3G connection was in a "slow" mode and
didn't recover well. It required a background ICMP to keep the damned
session nailed up to "fast". :-)



Adrian





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