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 tunable visibility of the provider's network to improve VPN performance. Generating accurate and fair TAs for each VPN while maintaining decentralization is a key challenge. The paper develops three decentralized TA generation schemes and validates their performance through simulations.