VoIP vs POTS (was Re: Operation Ghost Click)

Sean Harlow sean at seanharlow.info
Thu May 3 19:16:58 UTC 2012

On May 3, 2012, at 14:37, Brandt, Ralph wrote:

> Sean, do you know anyone who has successfully used either to place a
> call?  

Not to my knowledge.  Due to some family in government I'm sure I know someone who's authorized for one or the other, but I can't say the topic's ever come up.  I'm just a telecom geek who gets bored and reads obscure documentation.

> I think the weak spot is when the tower overloads nobody can dial
> anything, including the bypass..

That's certainly true, I don't know much about CDMA but in GSM if the RACH channel is flooded the phone won't be able to get through with a channel request and thus won't be able to do much of anything useful.  I believe a DoS based on this was demonstrated a few years back, so it is a legitimate concern.

The GAO actually did a report on both GETS and WPS a few years ago (http://www.gao.gov/new.items/d09822.pdf).  Report pages 63-64 (PDF pages 68-69) show completion rates during major events of the last decade, though comparisons to normal calling in the affected areas during the same period are not available.  Assuming that normal calls did have completion problems, it seems that GETS works well and WPS works until the cells get completely flooded as happened during the '09 Inauguration.
Sean Harlow
sean at seanharlow.info

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