CSC-SSM-10 supports 45 simultaneous connections which are enough for 500 users since the protocols that the module inspects (HTTP, FTP, POP3, and SMTP) are not "always on". The CSC-SSM-10 is equipped to handle 50 simultaneous FTP connections. Following link may help you
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...