3G data does not compute.

Discussion in 'iPad 2 Forum' started by Ncaissie, Mar 31, 2011.

  1. Ncaissie
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    Ncaissie iPad Enthusiast

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    I just hooked up my Ipad 2 to the Bell Canada network two days ago.
    When I login to their site to check my usage it says 35MB total.
    On my Ipad it says upload 4MB and Download 20MB. That is almost 1/3 difference.
    Has anyone noticed this? If it doesn't work why does Apple keep it there?
    Of course Bell says don't use the Ipad. I feel like they are ripping me off already.
  2. Tim SPRACKLEN
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    Tim SPRACKLEN iPad Legend

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    Wow - that's quite a difference. I wonder if the discrepancy might be due to the way that they compute the data volume? As you know, data are sent over the 3G network in a protocol known as TCP/IP. User data are encapsulated in 'packets' that 'transport' them over the carrier's network. These packets contain additional information - like IP addresses and help with error control. But they add overhead to the user data that are being transported. It's likely that the iPad is reporting net data flow - i.e. the actual underlying user data that are being transported, while Bell is reporting gross data flow - i.e. user data plus TCP/IP overheads.

    A TCP/IP packet has a more-or-less fixed overhead irrespective of the volume of user data contained in that packet. So user data that are fragmented into many small packets - and there are good technical reasons for doing this - will attract a significantly higher overhead than data that are fragmented into larger packets - because the TCP/IP overhead is the same in absolute terms for small and large packets but, of course, percentage-wise, it's larger when the user data in each packet are small.

    The percentage difference that you mention between the iPad's estimate and Bell's estimate sounds about right for a TCP/IP overhead discrepancy.

    Bell's argument would be - well, we have to carry the TCP/IP packets and it's not up to us how big or small the packets are. We charge for all the data the user asks us to carry - whether it's actual user data or the encapsulating packets.

    The iPad's argument would be that you're only interested in the net user data - probably, in this case, not a correct assumption.
    Tim
    Scotland
  3. volcanopele
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    volcanopele iPF Novice

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    Bah! That's nothing. According to Verizon (as logged in from the iPad2 in the Cellular Data tab in Settings), I have used 143 MB of my 1GB quota. According to the iPad under General->Usage, I have sent 33.9 MB of data and received 408 MB of data.

    Not that I am complaining.
  4. k7lvo
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    k7lvo iPad Fan

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    Don't count your chickens just yet. They may well be a bit behind on their page. Check back with them after little or no use for a day or two.
  5. Blackjack
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    Blackjack iPF Noob

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    Mine is spot on with ATT. And seems to be updated every few hours. Perhaps Verizon issue or people seeing this on ATT?
  6. Ncaissie
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    Ncaissie iPad Enthusiast

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    Your ISP may be behind like the others said. Mine seem to be projecting or ripping me off.
    I'm going to test them and turn off the 3G for they day.
  7. Ncaissie
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    Ncaissie iPad Enthusiast

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    So I got a detailed view of my data. It shows over 10MB of data when I was at home. I have a good router and wifi connection at home and there should not have been any 3G data during that time.
    It looks like I'm going to have to turn 3G off and only turn it on when I need it.
    That sucks.:mad:
  8. DontUnderstandMyIpad
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    DontUnderstandMyIpad iPad Guru

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    Perhaps certain apps don't get tracked?

    My results are miles off and I have no idea why. According to 3, the usage has been ~25GB, I use payg, which requires top-up after running out of data, so the figures should be fairly accurate.
    In contrast, the iPad think's, that only 10GB have been used:
    Sent: 621MB
    Received: 9.2 GB

    A lot of data was tethered to a laptop, so perhaps data used through MyWi doesn't get counted?
  9. Ncaissie
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    Ncaissie iPad Enthusiast

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    but when you are on Wifi the 3G should not be used at all right?
    I'm going to have to watch my iphone as well.
  10. DontUnderstandMyIpad
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    DontUnderstandMyIpad iPad Guru

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    True.

    The iPad always uses Wifi over 3G. There is no way to change that behavior, not even on a jb device.

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