Jio Fiber, strange connection issue experienced

[jasonbx]

I took Jio fiber connection 3 weeks back (399 plan). Last week around 11 pm, there was no connection suddenly. No sites loading, no dns resolution, not even pings to IPs were working. But strangely, youtube was working flawlessly through mobile app. The connection was down for around 5 hours but youtube continued to work. The modem was having steady green light. This baffles me. How did youtube work when even the pings (to even google DNS servers) were not working. Any idea? The problem got resolved automatically next morning.