Multiprotocol Label Switching (MPLS) Layer 3 VPNs are described in Internet Draft draft-ietf-l3vpn-rfc2547bis (RFC2547bis). MPLS Layer 3 VPNs allow a service provider to provision IP connectivity for multiple customers over a shared IP backbone, while maintaining complete logical separation of customer traffic and routing information. Each customer VPN consists of a several geographically dispersed sites. IP connectivity between sites is provisioned over the provider backbone.
There are two basic VPN models:
The overlay model, in which there is no exchange of routing information between the customer and the service provider
The peer model, in which routing information is exchanged ...