The sender transfers relevant session state to the receiver in such a way that every request can be understood in isolation, that is without reference to session state from previous requests retained by the receiver.
Visibility is improved because a monitoring system does not have to look beyond a single request in order to determine its full nature.
Scalability is improved because not having to store session state between requests allows the server to quickly free resources and further simplifies implementation.
[2] Contrast this with a traditional FTP server that conducts an interactive session with the user.
[4] HTTP cookies violate the REST architectural style because even without referencing a session state stored on the server, they are independent[clarification needed] of session state (they affect previous pages of the same website in the browser history) and they have no defined semantics.