knocking on port knocking

Port knocking has the potential to be an additional layer of protection available to highly security conscience network administrators.  However, just like any innovation, it is not without its weaknesses.  The author of the following article discusses some of the problems that can occur with port knocking.  The primary issue the author identifies is the use of new definitions for existing security concepts that are already well researched.  This has caused some administrators to fail to identify  the natural security limitations of port knocking.