How do network providers keep track of data used?

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I’m sitting here in a small closed room, deep in a building with poor reception. I click a link to open up a picture from the internet, and then it takes several minutes for the picture to load. If I had been outside, with better reception, the picture loads in under a second. So I am assuming the cell tower is continuously sending the information to my phone. Does the network read the amount of data sent by the tower or does it only count what my phone decrypts? Follow up question: if it only counts what my phone picks up, then wouldn’t that be exploitable?

In: Technology

TCP is a type of connection that enforces data delivery and is typically used by any software that needs to be sure it receives all the data, such as web browsers.

Vaguely speaking it goes something like this:

– Your phone says “Hey I need to access this web resource.”
– The tower says “Sure, I’m going to start sending some data now please acknowledge”
– Your phone didn’t receive that, so it asks again until it gets a response or it takes too long and times out
– Assuming the above is completed successfully, your phone sends an acknowledgement and the tower sends back “here’s a little bit of data…..did you get that?”
– Your phone didn’t receive the data so it doesn’t even know the tower tried to send anything….the tower waits a certain amount of time and thinks “Hmmm…I haven’t heard back yet…let me send it again” and sends the same information again.
– This time your phone receives the data and sends back “Hey yeah I got that, can you send the next bit of data?”

This pretty much goes back and forth until you either receive all the data, or the communication takes too long and closes the TCP connection.

It’s pretty much a back and forth of your phone asking for the next packet in a sequence and waiting until that comes back before asking for the next one. Things are generally re-broadcasted as necessary to continue the communication until it takes too long to respond and drops the connection, or the communication completes.

If you use 4g, all the data send over 4g is encrypted. Once the data gets in your phone the tower can’t see anything. The tower only tracks amount of data. Even if it reads your data it will be encrypted.

> Does the network read the amount of data sent by the tower

Yes. It counts the number of bytes being sent to your phone and the number of bytes being received from your phone by the network. The network doesn’t care about the content of those bytes. They can be encrypted or not, but the byte count still increases.

There are companies (like T-Mobile) that don’t count usage on certain apps. They still don’t look into the packet, they just know that “Hey, these packets are coming from IPs belonging to Netflix, so we don’t add them to the billing threshold”

> Does the network read the amount of data sent by the tower or does it only count what my phone decrypts?

Neither precisely, it considers what it is trying to send to you. If you have a bad connection it will be repeating itself a lot until you acknowledge receipt of a given packet. Requested data is split into small chunks called packets which are sent individually. Not getting a packet means they can just resend that bit rather than starting over entirely.

> if it only counts what my phone picks up, then wouldn’t that be exploitable?

Not really. Remember that everything is split into packets and acknowledged along the way or it will be sent again. If your phone is refusing to acknowledge packets then the connection isn’t going to work; it might drop and need to be reconnected or you simply won’t ever get anything beyond the first few packets of your requests.

Most likely they charge based on what you request to download and the details of what is actually transmitted is handled at the tower and typically ignored.