IPSec VPN configuration information.

Internet privacy and encryption information and protocols.

An IETF group working on PPP's extensions.

Counterpane Systems has exposed insecurities in Microsoft's Point to Point Tunneling Protocol.

PPTP technical specification by 3Com.

A GNU program allowing to encrypt arbitrary TCP connections inside Secure Sockets Layer (SSL).

PPTP server solution for Linux. Includes downloads, documentation and news.

Technologies used for creating secure VPNs. Various standards and protocols listed with links to related RFCs.

An IPsec reference implementation for Linux.