Reading about Slowloris attack:
Slowloris tries to keep many connections to the target web server open and hold them open as long as possible. It accomplishes this by opening connections to the target web server and sending a partial request. Periodically, it will send subsequent HTTP headers, adding to—but never completing—the request.
Looking at some examples, and writing one myself, it's quite easy to DOS the target by simply keeping the maximum connection limit open, recreating connections as the target times them out.
What is the point of sending subsequent HTTP headers after opening a connection with a partial request? Sending subsequent headers doesn't seem to reset the connection timeout.