tcprtt Measures the TCP handshake RTT using the stats(9) statistics framework
My coworker thought using 220.127.116.11 for the gateway monitor would suffice for a “is the internet up” monitor. Well, google rate limited us and I spent hours looking for the right approach.
Ultimately, it seems using ICMP for monitoring against public DNS, NTP, etc. servers is the wrong approach for some use-cases. Cisco’s IP SLA has the ability to perform a number of health checks from many protocols, so I set out to find something comparable for FreeBSD. Tcprtt looks like it could be a good solution for internet uptime monitoring that does not rely on ICMP.
Does this seem like a viable solution?
Updated by Jim Pingle 6 months ago
If we do include this it should also warn against using it arbitrarily, since some public services may also not react too well to repeated TCP sessions being opened and immediately closed. If it's a host you control it may be OK, but some things may flag it as suspicious behavior.