Emulating a cellular interface

Mikael Abrahamsson swmike at swm.pp.se
Sat Nov 6 01:09:41 CDT 2010


On Sat, 6 Nov 2010, Saqib Ilyas wrote:

> A friend of mine is doing some testing where he wishes to emulate a
> cellular-like interfaces with random drops and all, out of an ethernet
> interface. Since we have plenty of network and system ops on the list, I

I would say that a cellular interface doesn't really have random drops, 
then there is something wrong with it (at least if it's UMTS). A UMTS 
network has RLC re-transmits all the way between the RNC and the mobile 
terminal.

This means that a UMTS network has more characteristics of packet flow, 
stalls for hundreds of milliseconds or seconds (or even minutes, my record 
is 240 seconds), and then a burst of packets. Very jittery, but very low 
rate of packet loss.

Also, the terminal might go down in "idle", meaning that if you send a 
packet to it, it'll take 1-2 seconds for it to come out of idle, cellular 
resources allocated, and then the packets start flowing.

I don't have a good idea how to emulate this, the tools I've seen so far 
usually just emulate jitter, delay and packet loss, and not really the 
above behaviours.

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se




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