to provide remote offices or individual users with secure access to their organization's private network. A VPN can be
contrasted with an expensive system of owned or leased lines that can only be used by one organization; the goal of
a VPN is to provide the organization with the same secure data communications, but at a much lower cost.
A virtual private network uses the shared public infrastructure while maintaining privacy through security procedures
and tunneling protocols such as the Layer Two Tunneling Protocol (L2TP). In effect, the protocols, by encrypting data
at the sending end and decrypting it at the receiving end, send the data through a tunnel that cannot be "entered"
by data that is not properly encrypted. An additional level of security involves encrypting not only the data, but also
the originating and receiving network addresses. (from SearchSecurity.com)
SSL VPNs
SSL VPN implementations have become more popular due to the fact they are web-based. Only a standard browseris needed; no client software needs to be installed. They are firewall friendly as they use standard (secure) HTTPS
ports, whereas IPSec requires client software installed, extra protocol to add to the IP stack and firewall rules need
to be created due to non-standard ports being needed. Finally, SSL VPNs can be more cost effective...
SSL VPN Defined (opening ad?)
SSL VPN Migration? (Text)
OpenVPN (SANS Reading Room PDF)
OpenVPN Defined (Wikipedia)
OpenVPN Home (Proxy filters may block as remote access tool)
OpenVPN Download (SourceForge)
Cisco Solutions
Check Point Solution (SSL Network Extender)
SSL VPN Book (Packt Publishing)
IPSec VPNs
...on the other hand, IPSec VPNs make great point-to-point tunnels, often between two firewalls. Implementationsare fewer in number but, arguably, need to be more robust since they are online 24/7 and carry far larger traffic
volumes than smaller end-user deployments. They tend to be mission-critical connections, which ad hoc end-user
deployments usually are not. (from SC Magazine)
IPSec VPN Guide (NIST.gov PDF)
Home-based IPSec (Tutorial)
OpenBSD IPSec (Setup guide)
FreeBSD IPSec (Setup guide)
Microsoft Client (Admin guide)
Site-to-site IPSec VPN (Configs)