Layer 2 and 3 virtual private networks: taxonomy, technology, and standardization efforts

Virtual private network services are often classified by the OSI layer at which the VPN service provider´s systems interchange VPN reachability information with customer sites. Layer 2 and 3 VPN services are currently being designed and deployed, even as the related standards are being developed. This article describes the wide range of emerging L2 and L3 VPN architectures and technical solutions or approaches, and discusses the status of standards work. Some specific L2VPN and L3VPN technologies described here include virtual private LAN service, transparent LAN service, BGP/MPLS-based VPNs (RFC 2547bis), virtual router, and IPSec VPN approaches. We discuss recent and continuing standards efforts in the IETF 12vpn and 13vpn working groups, and related work in the pseudo-wire emulation edge-to-edge working group, as well as in some other standards fora, and describe some mechanisms that provide membership, reachability, topology, security, and management functions.