A growing trend is that network service providers and applications are integrated more closely through open APIs for better end-to-end performance. In particular, the provided-aided network information can help applications orchestrate their traffic for a better quality of experience, and is gaining a lot of attention from both the academia and the industry. However, enabling automated network-aware application optimization in today’s Internet is difficult because of the multivendor, multi-domain nature of carrier networks. In this paper, we introduce Sextant, a novel network information exposure system, taking a solid step towards enabling network-aware application optimization in carrier networks. Our work is driven by a real requirement from an international ISP, where timely, accurate distance information is critical to fully utilize its CDN caches deployed at different Point-of-Presence (PoP). We design a novel, flexible requirement model, allowing applications to specify their interests. The queries are efficiently carried out using our aggregation and incremental update algorithms. Evaluations demonstrate that our prototype system operates on top of real router software images, and can efficiently handle dynamics from multiple ASes.