The authentication engine parses {HEAD ~ the protect string} into one or more provider requests, and sends the requests to {TAIL ~ the authentication host} 
The authentication engine parses { HEAD ~ the protect string } into one or more provider requests , and sends the requests to { TAIL ~ the authentication host }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL