Even though I am only interested in TCP connect times, there is no TCP-layer test available on RIPE Atlas. Therefore, I leverage TLS and then look at the underlying metrics reported for TCP.
Moreover, I cannot do TLS measurement to port 80 because the test does not like to report TCP layer metrics in situations where the TLS handshake fails. I did discuss this with Philip Homburg at the hackathon. One possibility is to either a) refactor the TCP metrics into a specific TCP test or b) make the TLS test report TCP metrics even in situations where TLS handshake fails. I personally prefer b).
This not correct/complete. The Atlas traceroute measurement supports TCP. There is no reason to assume that this will not result in valid connect times. Just use a high enough starting ttl and only the target system will see the SYN packets. Philip