The Free On-line Dictionary of Computing (19 January 2023):

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)