When signalling protection is used by the 3GPP MC system, what does the IWF do?
Forwards the signalling packets without signalling protection
Removes 3GPP signalling protection from the signalling packets received from the 3GPP system
Applies applicable 3GPP signalling protection mechanisms for signalling packets received from the 3GPP system
Applies 3GPP signalling protection to the signalling packets sent towards the 3GPP system