Actually, the ASA platform will support NetFlows. Unfortunately, it is only available on the top end 5580 appliance. Here is a quote from a Cisco Rep..
Netflow logging is a high speed alternative to syslog. The 5580 will make good use of its features due to its performance levels. The development team will be watching customer reaction to this feature to determine what the next steps should be. Let your Cisco contacts know you interest.
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...