Overview of BGP/MPLS IP VPN
Definition
A BGP/MPLS IP VPN is a Layer 3 virtual private network (L3VPN). It uses the Border Gateway Protocol (BGP) to advertise VPN routes and Multiprotocol Label Switching (MPLS) to forward VPN packets on backbone networks. The VPN carries Internet Protocol (IP) packets.
Figure 1 shows the BGP/MPLS IP VPN model.
The BGP/MPLS IP VPN model consists of the following devices:
Customer edge (CE)
A device deployed at the edge of a customer network that has interfaces directly connected to the service provider (SP) network. A CE device can be a router, a switch, or a host. CE devices generally do not detect VPNs or need to support MPLS.
Provider edge (PE)
A device deployed at the edge of an SP network and directly connected to a CE device. On an MPLS network, PE devices process all VPN services and must have high performance.
Provider (P)
A backbone device deployed on an SP network and not directly connected to CE devices. P devices only need to provide basic MPLS forwarding capabilities. P devices do not maintain VPN information.
SPs manage PE and P devices. Customers manage CE devices unless customers authorize SPs.
A PE device can connect to multiple CE devices. A CE device can connect to multiple PE devices of the same or different SPs.
Purpose
A traditional VPN establishes full-mesh tunnels or permanent virtual circuits (PVCs) between all sites to forward VPN data. This method makes it difficult to maintain and expand networks. When a new site is added to an established VPN, a network administrator must modify the configuration of all edge nodes connected to this site.
A BGP/MPLS IP VPN uses a peer model that enables SPs and customers to exchange routing information. SPs are responsible for forwarding customer data without customer participation. A BGP/MPLS IP VPN is more scalable and easier to manage than a traditional VPN. When a new site is added, a network administrator needs to modify the configuration of the edge nodes serving the new site.
A BGP/MPLS IP VPN allows overlapping address spaces and overlapping VPNs so that VPNs can be flexibly deployed and expanded. BGP/MPLS IP VPN supports MPLS QoS and MPLS Traffic Engineering (TE) and therefore BGP/MPLS IP VPN is an important approach for IP network carriers to provide value-added services. BGP/MPLS IP VPN is now widely used.