Google Backup causes DSL to drop out

[#1]

This is a newly established ADSL2+ line that performs as expected. EXCEPT initiating Google Photos Backup on an iphone (ios 14.4) causes the DSL connection to fail. The connection re-establishes as soon as the app on the phone is closed.

I'm using a TP-Link Archer VR400, running diagnostics when the Google Photos Backup is open returns the following results:

Test xDSL Synchronization - PASS

Test WAN Connection - PASS

Network Connection Status Inspect (NCSI) - FAIL

I've tried disabling the router firewall to no effect.

Google Photos backup is the only app that causes this to happen.

Any suggestions would be appreciated.

[#2]

Its very likely caused by 'bufferbloat'. Many routers suffer from this problem whereby when upload traffic is high, they don't prioritorise acknowledgments required to downstream traffic and to maintain the connection, There are reports of the VR600 & VR900 suffering from the problem, so it is likely that the VR400 does also. If the VR400 has QoS facilities then limiting upload bandwidth may help to alleviate the problem.

[#3 · Accepted solution]

You need to limit the maximum bandwidth that Goole Photo Backup uses - there is an option to do that (I have done it some time ago - you can always google how to do it 😉). I'd limit it to 100kbps or less.

[#4]

Thanks folks. Indeed it was buffer bloat. I limited upload speed to 400kps via QoS on the router. Backup is now slow but steady with no line drops.