FortiGate1 has a gateway-to-gateway IPsec VPN to FortiGate2. The entire IKE negotiation between FortiGate1 and FortiGate2 is on UDP port 500. A PC on FortuGate2’s local area network is sending continuous ping requests over the VPN tunnel to a PC of FortiGate1’s local area network. No other traffic is sent over the tunnel.

Which statement is true on this scenario? http://kb.fortinet.com/kb/documentLink.do?externalID=FD35337

A.
FortiGate1 sends an R-U-THERE packet every 300 seconds while ping traffic is flowing.

B.
FortiGate1 sends an R-U-THERE packet if pings stop for 300 seconds and no IKE packet is received during
this period.

C.
FortiGate1 sends an R-U-THERE packet if pings stop for 60 seconds and no IKE packet is received during
this period.

D.
FortiGate1 sends an R-U-THERE packet every 60 seconds while ping traffic is flowing.