Advanced Networking Lab. Given two IP addresses, the estimation algorithm for the path and latency between them is as follows: Step 1: Map IP addresses to AS numbers. We use BGP routing tables to map an IP address to an AS number. Step 2: Infer AS paths between Ases. We use Qiu and Gao's methodology to infer AS paths between two ASes. Their methodology exploits the AS paths appeared in BGP routing tables. Step 3: Stitch path segments along the inferred AS path. Taking as input the inferred AS path from Step 2, we stitch the individual path segments as returned from the index. Here, the ending and beginning points of the segments must be exact IP address matches. We discuss approximation methodologies for cases without exact matches. Step 4: Rank stitched paths and select the best. Out of the multiple stitched paths from Step 3, we select the closest path to the real path. Massively distributed applications have become very popular in today's Internet. These applications require constantly updated information about the network-internal performance characteristics, such as round-trip delay, effective bandwidth, IP hop count, and loss rate. Today's Internet does not provide any such information, and applications and new services resort to proprietary measurements to obtain necessary information. Despite their novel methodologies of Internet-wide measurement and network performance estimation, these measurement systems are usually designed without much consideration for compatibility or inter-operability. Instead of performing measurements ourselves and generating active probes, we do no additional measurements on our own (other than for evaluation). We utilize existing measurements and extrapolate estimates for uncharted points. Our work is orthogonal to existing measurement systems, as our goal is to integrate diverse data sets and others' is to improve the accuracy in measurement. In this work we propose an algorithm to combine data sets and produce estimates. We focus only on delay and path in this work. Two data sets we consider are: hop-by-hop delay measurements from traceroute and BGP (Border Gateway Protocol) routing tables. The main idea is to segment traceroute outputs by the AS, and stitch up a path for a query using BGP routing tables. Fittingly, we call our algorithm path stitching. In every step of our algorithm, we face many sources of error. We illustrate challenges in dealing with those errors, and present a few heuristics to address them. Despite many sources of error, the evaluation results are promising. Router, PoP, or IP Prefix Clustering Intra-domain segment Inter-domain segment stitched path End-to-end delay graphs are generated on-the-fly Display statistics of stitched paths Stitched paths are displayed and animated on Google Map Query interface BGP routing table snapshots Traceroute outputs (IPv4 Routed /24 topology data set) toronto.kaist sibilla daemon prototype RouteViews and RIPE CAIDA Ark project demo-site.snu Web browser ( Data contribution Query Reply In this work, we propose to design an end-to-end delay estimation service, called Sibilla. The novelty of our system is that we utilize existing measurements and an infrastructure. Our delay estimation is based on a simple idea of path stitching. To provide the path-stitching as a service, we design and deploy our estimation service system on top of the Domain Name System (DNS). We deploy a Sibilla DNS server that receives a query between two hosts and replies with an estimated delay through the DNS interface. We take advantage of the fact that local DNS cache servers are distributed globally and exist in almost all ASes and improve the accuracy of our path stitching algorithm. * Sibilla is a female oracle figures in Greek and Roman times, offering cryptic predictions to those who sought to know the future (Sybil in English) The basic idea of our service system is to formulate a delay query between two hosts as a DNS query and let our Sibilla DNS server answer it. For example, when a user wants to estimate delay between two points A and B, the user submits a DNS query for A_B.latency.sibilla.com. The local DNS server forwards the query to our Sibilla DNS server, which in turn replies with delay estimation.