3.4.6.3 KeepAlive Timer Event

The KeepAlive timer fires every KeepAlive interval to trigger a send of a KeepAlive-Message across the GET Session from the server to the client. A KeepAlive event SHOULD trigger the server to send an encapsulated protocol message such as an SSTP_NOOP command<37>. Well behaved KeepAlive connections will see this event every KeepAlive interval when the session is idle.