1. SOAP
A system entity acting as a SAML requester transmits a SAML request element within the body of a SOAP message to a system entity acting as a SAML responder; The SAML responder MUST return either a SAML response element within the body of another SOAP message or generate a SOAP fault.
2. PAOS
PAOS： HTTP响应里携带SAML请求，在下一个HTTP请求里携带SAML响应。
3. HTTP POST Binding
The HTTP POST binding defines a mechanism by which SAML protocol messages may be transmitted within the base64-encoded content of an HTML form control
4. HTTP Redirect Binding
5. HTTP Artifact Binding
