[clue] [tech] Calculate total bandwidth usage for an interface using rrdtool

[Jim Ockers]

Charles W Downing wrote:
>
>
> On 06/10/2011 12:06 PM, Jim Ockers wrote:
>> Hi CLUEbies,
>>
>> Well as you know I send an e-mail to this list whenever I'm kind of 
>> stumped.  I have an OpenWRT based Linux system with a 3G phone 
>> interface.  Due to the marketecture of 3G data plans, I need to try 
>> to make sure this device does not exceed its monthly bandwidth 
>> allotment per our data plan, so we don't get a $60,000 bill, or 
>> something.  What I was thinking was, since we are allowed 5GB in a 
>> month, that I would figure out the total bandwidth used in the last 3 
>> weeks, and if the total bandwidth was 3/4 * 5GB then I would start 
>> throttling down the available bandwidth on the interface using tc and 
>> traffic shaping.
>>
>> This seems like it should not be too hard to do.
> Just an off the wall thought.  Does your provider keep a running total 
> of your usage during a billing period?  If so, it seems that you could 
> make a cron job to do the searching, leaving you to script the local 
> stuff.  BTW, I just checked and Verizon Wireless keeps a running total 
> of my/our usage to the nearest kB.
>
Yes, it's Verizon.  They update their statistics every 24 hours and 
don't have a convenient API to get the data, which makes it sort of 
manual.  The stats are not available in real time.  We are looking at 
nPhase which would overlay their APIs on top of Verizon, and might allow 
us to automate some of this.  We will probably do that anyway just to 
make sure we don't ever get a huge phone bill from an overage on one of 
these - like the guy who watched an NFL game on his cell phone, streamed 
from his slingbox, on a cruise ship.

Do you have real-time access to the running total of your usage to the 
nearest kB?  The Verizon people we've talked to act like it takes 24 
hours to update.

Even so there is a difficult inventory control challenge to make sure 
that system XXXXX, which might have 3G modem YYYYY, gets the memo from 
central-command that it should start throttling back its network usage.  
I'm trying to avoid saving the state on a central server because it'll 
use bandwidth which a) costs money and b) puts us closer to the 
bandwidth cap.  Some telemetry is necessary so if this turns out to be 
unavoidable then that's what I'd do.

It would be nice if the 3G modems would do this for us on their own, but 
they don't.

I like Dan Kulinski's idea of using iptables with "iptables-save -c" to 
save the state and counters, and it looks like that would make the data 
persist across a reboot.

Thanks,
Jim

-- 
Jim Ockers, P.Eng. (ockers at ockers.net)
Contact info: http://www.ockers.net/msi.html


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