The BGP/MPLS-Based VPN
In the peer-to-peer model, service providers are responsible for propagating routing information between the customer's sites, so a service provider who provides peer-to-peer VPNs for multiple customers will end up participating in routing for every one of those customers. This means that
There is a heavy burden on the service provider's routers to maintain multiple routing and forwarding tables, one for each customer using a peer-to-peer VPN across the service provider's network.
Each customer may use the same address space (in fact, many probably will, since most large networks are addressed out of one of the private, or nonroutable, IP address spaces).
BGP/MPLS-based VPNs solve these two problems and provide other advantages ...