See also:
  • http://www.antd.nist.gov/tools/cerberus/
    NIST Cerberus - An IPsec reference implementation for Linux.
  • http://pintday.org/hack/docs/vpn-24-minifaq.shtml
    OpenBSD VPN Mini-FAQ - IPSec VPN configuration information.
  • http://www.ietf.org/html.charters/pppext-charter.html
    Point to Point Protocol Extensions Working Group (PPPEXT ) - An IETF group working on PPP's extensions.
  • http://www.poptop.org/
    PoPToP - PPTP server solution for Linux. Includes downloads, documentation and news.
  • http://pptpclient.sourceforge.net/
    PPTP Client - A Linux, FreeBSD and NetBSD client for the Microsoft Point-to-Point Tunneling Protocol.
  • http://www.schneier.com/pptp.html
    PPTP Crack - Counterpane Systems has exposed insecurities in Microsoft's Point to Point Tunneling Protocol.
  • http://www.stunnel.org/
    Stunnel - A GNU program allowing to encrypt arbitrary TCP connections inside Secure Sockets Layer (SSL).
  • http://www.vpnc.org/vpn-standards.html
    VPN-Protocols - Technologies used for creating secure VPNs. Various standards and protocols listed with links to related RFCs.