In the example flow above, all depicted exchanges are "front-channel exchanges", that is, an HTTP user agent (browser) communicates with a SAML entity at each step. In particular, there are no "back-channel exchanges" or direct communications between the service provider and the identity provider. Front-channel exchanges lead to simple protocol flows where all messages are passed "by value" using a simple HTTP binding (GET or POST). Indeed, the flow outlined in the previous section is sometimes called the "Lightweight Web Browser SSO Profile".