Radius session

1,EAP 中继

client start，

NAS require identity，

client sent username，

NAS sent username to sever,

server generate MD5，send MD5 to client 

client send MD5*passwd to server

server chk

2，EAP 终结

client start，

NAS require identity

client send usename

NAS send MD5

client send passwd*MD5 to NAS

NAS send username and passwd*MD5 to Radius server