LTE: What does AMF signify ?

Question

Authentication Request message carries AUTN value which in turn has AMF field. What does it mean ?

Answer 1

AMF field of AUTN sets to 1 to indicate to the UE that the authentication vector is only usable for AKA in an EPS context. There is a separation bit which may 0 for non-EPS AKA and 1 for EPS context.