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ELI5: Today's Facebook outage (based on no inside info). Internet is designed in layers, like house built on a foundation. No coordination between layers - but there's dependency. 1st meaningful part is "layer 3" - the Internet Protocol (IP) network layer. [thread] /1
The DNS generally (not always) depends on what is known as the User Datagram Protocol (UDP) for transport - which is layer 4 on top of IP at layer 3. Then the DNS protocol itself happens at layer 7 on top of IP addressing/routing and UDP transport. /2
Specifically most DNS runs on UDP port 53 (aka UDP/53). There are different "port" numbers - unique numbers - assigned for specific uses. This makes operations/troubleshooting/interop easier. Find 'em all at iana.org/assignments/se… /3
