تفاوت بینProtocol Independent ServletوProtocol Dependent Servlet

what is difference between protocol dependent and independent servlet?

1. protocol dependent  is eligible to execute on http protocol but protocol independent can execute on any protocol but sun suggest only for http.
2. protocol independent extends GenericServlet.
3. protocol dependent extends HttpSevlet.
4. if it is dependent it will override doGet() and doPost()  method.
5. if it is independe it should override Init(), service() and  destroy()
6. protocol dependent  imports java.servlet.http