Ecway Technologies provides IEEE projects, software developments, and VPN services from its offices in Chennai, Trichy, Karur, Erode, Madurai, Salem, and Coimbatore, India. This research proposes a topology abstraction (TA) service to enable VPN service providers to share core topology information with VPN customers in a scalable way. The TA service provides visibility into the state of the provider's network to improve VPN performance. Key challenges include generating accurate and fair TAs for each VPN. The paper develops three decentralized TA generation schemes and validates their performance through simulations over various topologies.