The state machines defined in this document assume that the PaC and
 the PAA cache the last transmitted answer message. This scheme is
 described in Section 5.2 of [RFC5191]. When the PaC or PAA receives
 a retransmitted or duplicate request, it would be able to resend the
 corresponding answer without any aid from the EAP layer. However, to
 simplify the state machine description, this caching scheme is  omitted in the state machines below. In the case that there is not a
 corresponding answer to a retransmitted request, the request will be
 handled by the corresponding state machine.