Disappearing data on Vodacom and Cell C — 3G vs 4G
A recent investigation from MyBroadband revealed that data still disappearings from Android devices on Vodacom and Cell C’s networks, likely amounting to millions every month.
Vodacom and Cell C explained that it was due to how 4G works on mobile devices.
Even after toggling “mobile data” off on a smartphone, the Long Term Evolution (LTE) standard lets the device consume data in the background under certain circumstances.
“Under the 3GPP LTE standards, data traffic is possible across the 4G mobile network even when the ‘mobile data’ setting is turned off,” Cell C chief technology officer Schalk Visser previously told MyBroadband.
Essentially it boils down to how LTE networks handle phone calls.
On 3G, if you disconnect from the packet-switched data network, you remain connected to the old circuit-switched voice network.
With 4G, when voice-over-LTE is enabled, everything runs over the same packet-switched network. One of LTE’s key features is that it’s an all-Internet Protocol network.
Therefore, disabling mobile data while connected over LTE doesn’t completely disconnect the device from all data network elements. Otherwise, your phone will not ring when someone calls.
Vodacom confirmed that disappearing data happens because smartphones can use 4G mobile data even when the “mobile data” setting is turned off.
However, it explained the data may not always be signalling traffic purely to remain connected to the voice network.
“This is a function of how 4G is designed [and used by] the device, operating system, and relevant application developers,” a Vodacom spokesperson said.
“Testing has shown that small amounts of data are typically used for a connectivity test message in this way.”
In 2020, Cell C and Vodacom provided MyBroadband with the addresses our Android test devices communicated with, and they all belonged to Google:
- connectivitycheck.gstatic.com
- 173.194.69.192 (Google)
- play.googleapis.com
- 74.125.143.192 (Google)
Curiously, a subsequent test on Vodacom’s network came back with a completely different list of URLs.
Instead of the trace mobile traffic being routed to Google resources, it was routed to a variety of resources belonging to many companies — including Amazon, HP, Time Warner Cable, Verizon, China Telecom, and MIT.
However, this appeared to be a bug, and Vodacom said it worked with stakeholders to solve the problem.
Bug or not, the bottom line is that LTE lets devices consume mobile data even when it is disabled in your phone’s settings, while 3G does not.
MyBroadband tested the claim and confirmed it — disabling 4G solves the problem of disappearing data on Vodacom and Cell C.
No disappearing data on 3G — but it’s slow
We used the same four Nokia 5 devices from our previous disappearing data test and restricted them to only allow up to 3G connections.
Each device was loaded with airtime and data, and we turned off mobile data for the entire testing period.
The devices were all connected to a stable Wi-Fi network to prevent the need for mobile connections.
We also verified that no WASP services were active on any of the SIMs and that they were all configured not to use any out-of-bundle data.
We ran the same test as before, monitoring data and airtime balance daily. After a week, the balances remained exactly where they started.
When we re-enabled enabled, the data balances of the devices connected to Vodacom and Cell C’s networks immediately started depleting.
Although this confirms Cell C and Vodacom’s explanations, it does not answer the question they have so far shied away from.
Why do Telkom and MTN zero-rate the LTE signalling traffic from Android devices, but Cell C and Vodacom do not?
Testing by Wikus Steyn, words by Jan Vermeulen.
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