A client uses etags to verify the version of the resource model. This prevents the client from modifying (PUT) a version of the resource model that is not current. For example, if a client performs a GET on a server profile and receives an etag in the response header, modifies the server profile, and then updates (PUT) the resource model, the etag in the PUT request header must match the resource model etag. If the etags do not match, the client PUT request will not complete and a 412 PRECONDITION FAILED error is returned.