What type of pings does the TBBQM utilise.

After I setup my CF service on the same firewall (pfSense), I noticed the VM circuit was no longer responding to TBB pings, however the firewall is still allowing it, and if I pinged from a server it got a response, likewise both UDP and ICMP traceroute got responses.

After I setup a new firewall to handle the CF line, I decided to keep VM on the old one until the service is terminated and now its on its own again, TBB pings work again.

The thing thats making this unclear is pings get a response from other sources, so if possible can it be verified what type of pings TBB use, thank you.