ONOS-426 - make the unit of Bandwidth clear

Change-Id: I6f23f01306ece906fb6a6a894a52a6369983eeed
diff --git a/core/api/src/main/java/org/onosproject/net/AnnotationKeys.java b/core/api/src/main/java/org/onosproject/net/AnnotationKeys.java
index 6ccb519..8b55fa3 100644
--- a/core/api/src/main/java/org/onosproject/net/AnnotationKeys.java
+++ b/core/api/src/main/java/org/onosproject/net/AnnotationKeys.java
@@ -61,6 +61,7 @@
 
     /**
      * Annotation key for bandwidth.
+     * The value for this key is interpreted as Mbps.
      */
     public static final String BANDWIDTH = "bandwidth";