IPSec (Internet Protocol Security)

IPSec (Internet Protocol Security) is the next-generation network layer crypto platform which can be found on routers, firewalls, and client desktops, particularly in virtual private networks. It is a framework for a set of security protocols at the network or packet processing layer of network communication. IPSec provides two choices of security service: Authentication Header (AH), which essentially allows authentication of the sender of data, and Encapsulating Security Payload (ESP), which supports both authentication of the sender and encryption of data as well.

NENA 75-001, NENA Security for Next-Generation 9-1-1 Standard (NG-SEC)

Wikipedia definition