esp…

http://www.rfc-editor.org/rfc/rfc4303.txt

ESP can be used to provide confidentiality, data origin
   authentication, connectionless integrity, an anti-replay service (a
   form of partial sequence integrity), and (limited) traffic flow
   confidentiality.  The set of services provided depends on options
   selected at the time of Security Association (SA) establishment and
   on the location of the implementation in a network topology.