EAP failure message to the RP. As part of the EAP method, the client sends an EAP channel-binding message to the IdP (Section 2.2.2). In the channel-binding message, the client identifies, among other things, the RP to which it is attempting to authenticate. The IdP checks the channel-binding data from the client against the data provided by the RP via the AAA protocol. If the bindings do not match, the IdP sends an EAP failure message to the RP.