PiX Firewall by design is a firewall, (security levels, nat-control, packet inspection at level 7, etc) CBAC does emulate the packet inspection that a PIX Firewall does, here is a link with pretty good information about the CBAC capabilities and the scenarios in which you may use it:
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...