Monitoring the status of MPLS VPN and VPLS based on BGP signaling information

The flexibility and ease of setup of MPLS Virtual Private Networks (VPNs) and Virtual Private LAN Service (VPLS) motivate the large and growing user base of these services. It is therefore important for an Internet Service Provider (ISP) to ensure their uninterrupted operation, as also specified in service contracts. Although network monitoring is regarded as an essential activity to pursue this goal, existing monitoring approaches are often limited in the ability to capture the effects of VPN-related events such as reconfigurations and device failures. In this paper we provide several contributions: 1) a methodology to monitor the status of MPLS VPN and VPLS over time, which considers the BGP signaling messages sent by routers to propagate VPN information; the methodology is founded on an analysis of the observable effects of network events; it also envisions presenting the status of MPLS VPN and VPLS in an easy-to-understand visual form that allows to immediately spot potential anomalies; 2) an extensive discussion of the tradeoff between scalability of our monitoring approach and visibility of the effects of network events; 3) an architecture and prototype implementation of a tool based on our methodology; 4) a thorough experimentation of our approach in a realistic network scenario. As an example, the methodology allowed us to spot a subtle routing anomaly triggered by an implementation choice in the routing software used in our experiments.