Why does SIML give different numbers than my ISP?

[artki]

My ISP has me on a 150gb a month cap so it's important to get accurate usage numbers.

The numbers my ISP lets me see on their site often differ greatly from the SIML numbers - sometimes by almost 2gb in one day!  The differences are almost always higher on the ISP side.

I have the only computer on this connection.  I often put it in sleep mode - while it's sleeping the gateway is still turned on.  Could there be traffic in and out of my gateway that SIML doesn't see?

Here are some numbers from 6-23 to 7/1.  (didn't have SIML working all the time before that)

      total      downloaded   uploaded

07-01-2011   4.90 GB       3.87 GB       1.03 GB
06-30-2011   4.47 GB       3.67 GB       0.80 GB
06-29-2011   4.63 GB       3.67 GB       0.96 GB
06-28-2011   5.74 GB       5.21 GB       0.53 GB
06-27-2011   4.42 GB       2.84 GB       1.58 GB
06-26-2011   5.89 GB       4.07 GB       1.83 GB
06-25-2011   3.34 GB       2.70 GB       0.64 GB
06-24-2011   4.29 GB       3.06 GB       1.23 GB
06-23-2011   4.32 GB       3.35 GB       0.97 GB

---------------------------------------

Network Daily Traffic Report
      total      Up      Down
07/01/2011   3.75GB      717.71MB   3.05GB         
06/30/2011   3.75GB      615.34MB   3.15GB         
06/29/2011   4.64GB      849.65MB   3.81GB         
06/28/2011   3.81GB      275.62MB   3.54GB      
06/27/2011   3.98GB        1.78GB   2.19GB      
06/26/2011   4.03GB      870.42MB   3.18GB         
06/25/2011   3.50GB      603.08MB   2.91GB      
06/24/2011   3.02GB      939.25MB   2.10GB         
06/23/2011   3.93GB      802.14MB   3.15GB      

Note the HUGE differences on June 24, 26, 28 and July 1.  Each over a gig.

I'm going to show this to the ISP as well but before getting into a confusing discussion with their "tech support" I'd like to know if anybody has an idea as to what's going on.

My computer is running win7/64.

[Shane]

If your computer is the only thing using the internet then the numbers should be closer unless your ISP is counting something more as usage.

The program watches each packet that goes in and out of the computer it is running on. So unless you have something else on your home network, or someone else is using your connection (Like a non password protected wireless connection)

So there are 3 reason why the numbers are off.

1. Your ISP is reporting wrong, or counting something else as usage.
2. Something else on your network is using the net as well.
3. For some reason the monitor isn't seeing the packets going in or out.

My program uses winpcap to see the packets. If the program is running the whole time the computer is then the numbers should be right on track.

Shane

[Evan]

Most likely something else is using the connection. Like Shane said, this could be someone using an unsecured wireless connection or if you have a smart phone or tablet and are using your home wireless network. Can you think of anything like that? If you can't, then you can log into your router and look at all the devices that are currently connected to your router.

Evan

[artki]

> Most likely something else is using the connection. Like Shane said, this could be someone using an unsecured wireless connection or if you have a smart phone or tablet and are using your home wireless network. Can you think of anything like that?

The WiFi on my gateway is turned off and always has been.  The only thing plugged into it is the ethernet cable, the phone line and a power cord.

> can log into your router and look at all the devices that are currently connected to your router.

Well, the menus on the gateway are fairly murky to me but I was able to verify that the wifi is disabled and there's nothing else but that 1 ethernet cable!

[artki]

> 1. Your ISP is reporting wrong, or counting something else as usage.
> 2. Something else on your network is using the net as well.
> 3. For some reason the monitor isn't seeing the packets going in or out.

2.  Nobody else on the network
3.  I wouldn't know but I assume you know what you're doing.  Also, the previous bandwidth monitor I used (Freemeter) was reporting the same kind of discrepancies (I used that for a couple of weeks before switching to your program).  That program didn't use winpcap so there are two different metering methods on my computer that don't even come close to the ISPs.

Therefore I assume that I need to look at reason #1.
But I wanted to hash this out with you guys before subjecting myself to ATT "tech support".

[Evan]

If you only have one device connected then that does sound odd. What you might want to do to really have something good to say to them is try having your computer completely turned off for a 24 hour period (go to the lake or something) so that there was no way that your computer contributed to the bandwidth at all. That way you can tell them that on the 4th (for example) you didn't even have your computer on and ask them how it's possible. You could also take it a step further and on another day don't even have your router or modem powered on and see if they report any usage. Sure you'll be out of internet use for a day or two but it'll help your case. 

Evan

[Shane]

The fact that you have used 2 different monitors makes me think it is the ISP as well. In all honesty, a ISP who give you a cap doesn't surprise me they are hire that what you actually used.

I have worked for ISP's before (Years ago, not to many of them really care about the users). Either they are monitoring high on purpose, or have a mistake some where.

Shane