Trusted Delivery Networks VPN
Trusted VPNs (sometimes referred to APNs - Actual Private Networks) do not use cryptographic tunneling, and instead rely on the security of a single provider’s network to protect the traffic. In a sense, these are an elaboration of traditional network and system administration work.
* Multi-Protocol Label Switching (MPLS) is often used to overlay VPNs, often with quality of service control over a trusted delivery network.
* Layer 2 Tunneling Protocol (L2TP) which is a standards-based replacement, and a compromise taking the good features from each, for two proprietary VPN protocols: Cisco’s Layer 2 Forwarding (L2F) (now obsolete) and Microsoft’s Point-to-Point Tunneling Protocol (PPTP) .