@subacini balakrishnan, HTTP calls to both the NameNode and the DataNode will utilize SSL. Since it utilizes SSL for the data transfer performed with the DataNode, the bytes in transit are encrypted and cannot be read by a man-in-the-middle attacker.
The way this works is that the HTTP client first initiates a call to the NameNode using either the "http" or "https" scheme. For a file read or write operation, the NameNode will select an appropriate DataNode and send an HTTP 302 redirect response back to the client telling it to reconnect to that DataNode to complete its request. When the NameNode performs this redirect, it detects the scheme of the incoming call that was sent to it and preserves that scheme in the Location header of the HTTP 302 redirect response. Thus, for a request originating at the NameNode via "http", the redirection will point to an "http" URL on a DataNode, and for a request originating at the NameNode via "https", the redirection will point to an "https" URL on a DataNode.
