The Negotiate HTTP authentication scheme is defined in RFC 4559.
If a server receives a request for a protected resource it responds with status 401 Unauthorized
and a WWW-Authenticate: Negotiate
header. The client reissues the original request with a WWW-Authenticate: Negotiate [gssapi-data]
header. The server uses the gssapi-data
to attempt to authenticate the client; if successful the request continues and a 2xx
response can also carry a WWW-Authenticate
response header containing the final leg of an authentication.