nIP
security (IPSec) can function in three roles relative to a
client:
uClient
(Respond Only) in which the server uses IPSec, if the client is
using it first
uServer (Request Security) in which the server
uses IPSec by default, but will discontinue using IPSec if it
is not supported by the client
uSecure
Server (Require Security) in which the server only communicates
via IPSec