vSBC fails to establish IMS-AKA session

Hello,

I faced following problem during IMS-AKA client testing: registration procedure goes in accordance with this scheme on the picture below. In first "REGISTER/401" transaction the Client and the SBC exchange data about their ports to be used for further communication (step 2 on the scheme). Then Client sends TCP SYN to negotiated port (step 3 on the scheme), but SBC somehow ignores this SYN, however, negotiated port on SBC side is opened and in state "LISTENING". It looks as if the IPsec was not supported on this SBC. I have this doubt because I cannot find out these