EAP is an end-to-end framework; it provides for two-way communication between a peer (i.e., client or Individual) through the EAP authenticator (i.e., RP) to the back end (i.e., IdP). This is precisely -- and conveniently -- the communication path that is needed for federated identity. Although EAP support is already integrated in AAA systems (see [RFC3579] and [RFC4072]), several challenges remain: