The main reason that IPsec is so powerful is that it provides security to IP, which is
the basis for all other TCP/IP protocols. In protecting IP, you are protecting pretty
much everything else in TCP/IP as well. An important issue, then, is how exactly do
you get IPsec into IP? There are several implementation methods for deploying
IPsec. These represent different ways that IPsec may modify the overall layer
architecture of TCP/IP