V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

IPSEC
       Internet Protocol SECurity (org., Internet, IETF, DES), "IPSec"


The Free On-line Dictionary of Computing (30 December 2018):

IPsec

    ("IP Secure"?) A protocol
   that provides security for transmission of sensitive
   information over unprotected networks such as the
   Internet.  IPsec acts at the network layer, protecting and
   authenticating IP packets between participating devices
   ("peers"), such as Cisco routers.

   IETF IPsec (http://ietf.org/ids.by.wg/ipsec.html).

   (2002-05-06)