On the security scale, PPTP VPNs are the least secure, but, when set up appropriately, can actually be pretty good for many organizations that don't need FBI style protection. PPTP VPNs also happen to be easy to use from the client perspective since most modern operating systems include a PPTP client. On the server side of the equation, since PPTP does not require a complete certificate architecture (PKI) to get up and running, these VPN types are easier to get working. For the most secure PPTP, disable any encryption method below 128-bit and use a reasonable authentication method, such as EAP or MS-CHAPv2 (which supports rotating keys). Further, make sure your users are always using strong passwords.
On the other hand you have the ASA 5520 so make use of it properly. the ASA is a vpn appliance supporting a wide range of deployment and application environments, the Cisco ASA 5520 Series SSL/IPsec VPN Edition will delivers maximum value to your organization with the most comprehensive set of Secure Socket Layer (SSL) and IP security (IPsec) Virtual Private Network (VPN) features, performance, and scalability.
The link below will help you setup Remote VPN on ASA using the cisco vpn client on your Microsoft XP computer
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...