The method, called Dead Peer Detection (DPD) uses IPSec traffic patterns to minimize the number of IKE messages that are needed to confirm liveness. DPD, like other keepalive mechanisms, is needed to determine when to perform IKE peer failover, and to reclaim lost resources.
DPD is the mothod of keepalives implemented on Cisco routers/FWs/vpn3000 and possibly most other devices. It is configured via "crypto isakmp keepalive" is the CLI to set it.
Now my memory might serve me wrong but there used to be a keepalive mechanism in place before :-) Nowadays isakmp keepalives and DPDs are used interchangeably.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...