I have also done extensive speed tests with 515Es and they always report very poorly for me as well. Not really sure the reason for this but I finally replaced mine with a router running NAT. Performance increased after 6.3(5) to 7.0(8) upgrade but still doesn't approach my 3620 router in terms of the test results.
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...