SSL heartbeat design

Question

So, about Heartbleed again, why does SSL/TLS allow the client to specify the message and its length in the heartbeat requests, rather than sending a simple ping?

Answer 1

Heartbeat requests are intended for use with connectionless SSL over UDP. A simple ping tells you only that the computer at the other end is up (or not); by including a payload, a program can associate heartbeat requests with specific transactions, detect dropped or out-of-order replies, and do other things that a simple "are you there?" can't do.

That said, I suspect the real reason that heartbeat requests have a payload is that they were modeled on ICMP "echo" requests, without understanding why ICMP echo permits a payload. The ICMP echo payload is intended for low-level network troubleshooting.