What ports does GTM use when measuring RTT

Hi, I'm trying to configure GTM pools using round trip time load balancing method without using ICMP in case it is blocked by firewall headed to LDNS.

According to documentation, RTT can be measured by using several metrics collection protocols other than ICMP, such as TCP/UDP/DNS_REV/DNS_DOT

https://my.f5.com/manage/s/article/K6480

I've tried some tests by exculding ICMP from metrics collection protocols and choosing TCP/UDP/DNS_REV/DNS_DOT on the selected check box, but it still seems to check with ICMP echo.

I would like to make sure what ports GTM measures RTT when using those protocols so that they can be allowed on firewall.