minor: adding bwm-ng note

Author: Sam Kleinman

source/administration/production-notes.txt

@@ -244,3 +244,11 @@ Key fields from ``iostat``:
 
 - ``avgrq-sz``: average request size. Smaller number for this value
   reflect more random IO operations.
+
+bwm-ng
+~~~~~~
+
+`bwm-ng <http://www.gropp.org/?id=projects&sub=bwm-ng>`_ is a
+command-line tool for monitoring network use. If you suspect a
+network-based bottleneck, you may use ``bwm-ng`` to begin your
+diagnostic process.