Multi-WAN setup: frequent ISP outage reason


Hardware: x86 J1900 quad core 2.0Ghz cpu.
Software: Openwrt 18.x mwan3 package with 3 ISPs, 2x100 Mbps isp1 + 500 Mbps isp2.

The issue I am facing is that isp1 goes down for a minute and comes back up.

Happens like that every hour or so.

This means there are ping drops, due to which mwan3 removes the link from active, then after a minute ping returns, mwan3 adds back the link to active.

I want to know if it's the router or the ISP.

CPU/memory usage is always very low so router hardware is not the limit.

Is it because I am using the link more than ISP's provisioned rate?

A plot of the ping, jitter and drops seems to indicate that first jitter value shoots up, then a bunch of ping drops happen.