ts of Layer 3 MPLS VPNs is that the provider handles all the meshing and can provide any-to-any connectivity over a multitude of interface types. Previously, if a customer wanted to mesh its remote locations, it had to pur- chase leased lines and build a mesh of permanent virtual circuits (PVCs). The rout- ing architecture and propagation of routes was up to the customer; the provider only ensured connectivity. With Layer 3 MPLS VPNs, all that is required is the advertisement of the routes to the provider edge, and the provider handles the rest. The only drawback to this solution is that the provider may not have the geo- graphic footprint to reach all the customer locations; it can be cost-prohibitive for the customer to purchase a local loop to the nearest provider edge router in the provider's POP. This is a limiting factor with MPLS deployment, especially for orga- nizations that have international locations. Virtual Router VPNs The objective of a Layer 3 virtual router VPN, which is currently an IETF Internet Draft, is to provide per-VPN routing, forwarding, QoS, and service management capabilities. This VPN service is based on the concept of virtual router, which has exactly the same mechanisms as a physical router and, therefore, can inherit all existing mechanisms and tools for configuration, deploy- ment, operation, troubleshooting, monitoring, and accounting. Multiple virtual routers can exist in a single physical device, and virtual routers can be deployed in various VPN configurations. Direct virtual router-to-virtual router connectivity can be configured through Layer 2 links or through a variety of tunnel mechanisms, using IP- or MPLS-based tunnels. Also, multiple virtual routers can be aggregated over a backbone virtual router. This architecture accommodates various backbone deployment scenarios, including situations in which the VPN service provider either owns the backbone or obtains backbone service from one or more other service providers. As shown in Figure 9.24, a VPN customer site is connect