docs: reorder sections

docs/howitworks.rst

@@ -551,28 +551,6 @@ and trigger ``DEL_ROUTE`` messages propagated upstream for each route
 associated with that stream if the stream is disconnected for any reason.
 
 
-Disconnect Propagation
-######################
-
-To ensure timely shutdown when a failure occurs, where some context is awaiting
-a response from another context that has become disconnected,
-:class:`mitogen.core.Router` additionally records the destination context ID of
-every message received on a particular stream.
-
-When ``DEL_ROUTE`` is generated locally or received on some other stream,
-:class:`mitogen.parent.RouteMonitor` uses this to find every stream that ever
-communicated with the route that is about to go away, and forwards the message
-to each found.
-
-The recipient ``DEL_ROUTE`` handler in turn uses the message to find any
-:class:`mitogen.core.Context` in the local process corresponding to the
-disappearing route, and if found, fires a ``disconnected`` event on it.
-
-Any interested party, such as :class:`mitogen.core.Receiver`, may subscribe to
-the event and use it to abort any threads that were asleep waiting for a reply
-that will never arrive.
-
-
 Example
 #######
 
@@ -597,6 +575,28 @@ When ``sudo:node22a:webapp`` wants to send a message to
 .. image:: images/route.png
 
 
+Disconnect Propagation
+######################
+
+To ensure timely shutdown when a failure occurs, where some context is awaiting
+a response from another context that has become disconnected,
+:class:`mitogen.core.Router` additionally records the destination context ID of
+every message received on a particular stream.
+
+When ``DEL_ROUTE`` is generated locally or received on some other stream,
+:class:`mitogen.parent.RouteMonitor` uses this to find every stream that ever
+communicated with the route that is about to go away, and forwards the message
+to each found.
+
+The recipient ``DEL_ROUTE`` handler in turn uses the message to find any
+:class:`mitogen.core.Context` in the local process corresponding to the
+disappearing route, and if found, fires a ``disconnected`` event on it.
+
+Any interested party, such as :class:`mitogen.core.Receiver`, may subscribe to
+the event and use it to abort any threads that were asleep waiting for a reply
+that will never arrive.
+
+
 .. _source-verification:
 
 Source Verification