MGCP 什么是lockstep状态

In the Media Gateway Control Protocol (MGCP) [2], when an endpoint
   operating in "step" mode generates a Notify, it will enter the
   notification state, where it waits for a response to the Notify.
   Furthermore, the endpoint must wait for a new NotificationRequest
   before it can resume event processing.  As long as the endpoint is
   waiting for this NotificationRequest, we say that it is in the
   lockstep state.

 An endpoint that is in the lockstep state cannot perform any event
   processing and therefore also cannot generate a new Notify.
   Endpoints should only be in the lockstep state for a very short time.
   However, in adverse conditions, an endpoint could potentially end in
   the lockstep state without the Call Agent realizing it.  Clearly,
   this could have very negative consequences in terms of the service
   provided.