The roadwarriors carol and dave set up a connection each to gateway moon using EAP-TTLS authentication only with the gateway presenting a server certificate and the clients doing EAP-MD5 password-based authentication. In a next step the EAP-TNC protocol is used within the EAP-TTLS tunnel to determine the health of carol and dave via the TNCCS 2.0 client-server interface compliant with RFC 5793 PB-TNC.
Unfortunately carol sends her first PB-TNC batch with a wrong version number and dave sends a PB-TNC message not supported by moon with the NOSKIP flag set. Therefore both connection setups fail due to fatal PB-TNC errors.