whitespace

Author: drbruced12

preface.rst

@@ -81,7 +81,7 @@ traffic to securing the routing system that underpins the
 Internet. Security is a never-ending set of challenges and there will
 always be new threats and solutions. This book aims to lay the
 foundation so you can understand the network security landscape as it
-continues to evolve. 
+continues to evolve.