Excessive data usage

I found your logs. (We have them here too, which is at least a tiny fraction of that 53 GB)

For now I’d recommend stopping Tailscale when not in use via iOS (in Settings > VPN and flipping the “Status: Connected” switch), not via the Tailscale app itself until we figure out what’s going on. (The iOS Settings way stops it much more aggressively.)

One thing I see is that one of your machines in particular (NUC) but really all of them to a lesser extent seem to be flipping back and forth between London and Frankfurt as their nearest “home” connection, even though I thought our code did a good job at preventing such oscillation. That then means they’re sending your phone a bunch of updates about where their new location is. At least in the next Tailscale release, that bandwidth is smaller. But they shouldn’t be flipping back and forth between London and Frankfurt anyway.

While that’s inefficient, it doesn’t explain 3.5 GB in a day. In the past 72 hours there have only been 300 flips back and forth.

I’ll look into it more with colleagues either tomorrow or next week.

Good to see that you’re able to trace the data usage. I think I confused days, the excessive usage occurred on Monday instead of Tuesday.

For now I switched off cellular usage for Tailscale on my phone.

Looking forward to a solution!

Any progress on this issue @bradfitz?

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We use tailscale for our iot network. For ethernet stations it is not a problem, but tailscale is using way to much traffic on mobile usage (3G, 4G).

This was confirmed by the tailscale support team.

I would say, you cant use it under this conditions - this is for us a really bad thing and we have to find an alternative to tailscale.

Yes, we are aware of this; it’s an area that we’re working on, and each release has gotten a bit better.

If it’s feasible, try to stop the Tailscale while not using it and start it when needed.

This will be much better in 1.4.0. See 1.3.293 is released (a 1.4.0 pre-release)

Just out of curiosity, what type of info is recorded at your side in the logs?

It’s mostly about NAT traversal connectivity and firewall decisions. Not the contents of data packets, for instance.

You can see it yourself on your local machine via journalctl, Console.app, or C:\Windows\System32\config\systemprofile\AppData\Local\Tailscale\Logs, depending on OS.

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I’ll have a look, thanks :grin:.

@sevenymedia, do you happen to also use ZeroTier? We recently discovered an issue where ZeroTier and Tailscale didn’t work at the same time and cause ZeroTier to flood traffic non-stop over Tailscale.

In any case, we think we’ve mitigated that, and we’ve also made Tailscale idle much more nicely with 1.4.0 which was just released. Try it out and let us know?

  • Brad

I don’t use ZeroTier.

I just installed 1.4.0 on my nuc. I still have cellular usage disabled on my phone, how do I know if it’s safe to turn it on again without flying through my plan?

Do you use any other VPN or networking software on that NUC?

I guess I’d recommend turning it back on but keeping an eye on it.

Do you use any other VPN or networking software on that NUC?

No, it’s a pretty clean Ubuntu 20.04 installation, only ‘custom’ thing is CSF as firewall instead of the default.

I guess I’d recommend turning it back on but keeping an eye on it.

Alright, I’ll give it a try

@sevenymedia, I’m now running tailscaled on an LTE modem (with $10/GB data) so I’m now keeping a close eye on this.

Based on my limited data so far running it idle for 2 hours, it looks like it’s on track to use 8.2 MB/day down up, and 6 MB/day up.

But… that’s without a number of the new Tailscale 1.4 protocol optimizations activated server side. It’ll be dropping a fair bit I think. I’ll post new numbers next week when those start to be enabled. (You won’t need to restart your client…)

We rolled out the optimizations for a few test networks today. An idle machine on my home network on an LTE modem is now averaging 0.09 kBps, or 7.59 MiB/day, or ~231 MiB/month. So on my $10/GB Google Fi data SIM, that’s about $2.25/month.

And upload is about half that. So maybe $3/month, depending on how ISPs charge.

There’s more we’ll be doing, though. (In addition to my personal LTE bill, we also pay for the server’s bandwidth, so it’s in our best interest to keep reducing it)

We’ll be enabling this server-side optimization (for 1.4+ clients) sometime today or this week.

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Actually, for the past two hours it’s only been 0.08 kBps, so a bit better than the numbers I’d posted above.


I have been watching this thread as I am having the same issue.

I am using iOS and then connecting to an Ubuntu 20.4 host which routes a couple of internal subnets essentially.

I had issues at the end of last year where I used 10GB in one day, the only thing that I have connect at the other end is Home Assistant with literally a single toggle option so I doubt that is using much data at all.

I saw this thread, updated all my devices and tried again. On the 1st of Feb I chewed through 8GB of data, and my phone got really hot. I just checked and at the time of the issue I was using iOS version 1.2.8 (which was the latest at the time).

I rebooted my device, turned Tailscale off and haven’t had any further issues. It definitely feels like Tailscale is the issue here, I have very similar usage habits with TailScale turned off and don’t have data issues. It also seems random, like the second time I had the issue, it had been around a month without it using much data at all.

If you think that there has been fixes after the 1st of Feb (NZT) I can give it another go, but my issue is that it runs through so much data in a short space of time it hard to catch and should a few hours go by I can lose GB’s worth of mobile data.

Happy to work with anyone at Tailscale to investigate if they want to touch base with me. I really like the product so I am keen to try and assist in resolving the problem.

Are you using any other VPN/networking/routing software? Tailscale 1.4.x works around a problem with ZeroTier and Tailscale running at the same time that generated a crazy amount of useless traffic.

No other VPN or routing software on the iOS device or the Ubuntu host either.

iOS mobile data is showing usage of 1.2GB in the past 10 hours, in the past this hasn’t lined up with my actual usage though so I am not 100% sure its accurate (for some reason). The past 10 hours I have hardly been out of wifi reception

What are your Tailscale IPs?

Debugging from the Ubuntu side would be easier. Do you see the same amount of traffic there?

We can also debug together if you book some time: Calendly - Brad Fitzpatrick