Free and open geodata: From shadows to reality - Simon Greener

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AUTHOR: SIMON GREENER

This talk will attempt a review of the geospatial data space within Australia. The talk will outline who the main players are, what spatial data is available, and the licensing options that cover their use. An assessment of the licenses will be made. In particular the talk will outline the data that is available for free and, and after establishing the various uses of that data, assess how important that data is to various sectors and individuals within society and how it might benefit society as a whole.

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Free and open geodata: From shadows to reality - Simon Greener

  1. 1. Sequoia: Virtual-Tree Models for Internet Path Metrics Rama Microsoft Research Also: Ittai Abraham (Hebrew Univ.) Mahesh Balakrishnan (Cornell) Archit Gupta (Univ. Wisc.) Fabian Kuhn (EPFL) Dahlia Malkhi (MSR) Kunal Talwar (MSR)
  2. 2. Introduction Goal: Model properties (latency, bandwidth) of paths between Internet end hosts
  3. 3. Applications • “what’s the server with the largest bandwidth that the client can download content from?” – Content distribution • “what’s the relay node that gives the shortest delay VoIP connection between two users?” – VoIP routing • “what’s the best server to coordinate the online game between a set of players?” – Online gaming
  4. 4. Sequoia Virtual Trees • Network embedding into trees R —Leaf nodes (A, B, C, R) are end hosts Internet A B C
  5. 5. Sequoia Virtual Trees • Network embedding into trees R —Leaf nodes (A, B, C, R) are end hosts t —Inner nodes (s, t) are s “virtual” A B C
  6. 6. Sequoia Virtual Trees • Network embedding into trees R 80 —Leaf nodes (A, B, C, R) are end hosts t 10 —Inner nodes (s, t) are s “virtual” 2 1 20 —Edge weights model path property A B C
  7. 7. Accuracy of Virtual-Tree Models Relative Error PlanetLab King PlanetLab Latency Latency Bandwidth 125 nodes 2500 nodes 390 nodes Median 14 % 20 % 24 % 75th p.c. 22 % 35 % 41 % 90th p.c. 50 % 56 % 65 %
  8. 8. Distance Labels a.k.a ‘‘Coordinates’’ • Distance Label = Path to the Root R – Example: A: (s,t,R) and C: (t,R) 80 • Trivial to estimate quality of paths t – Latency: d(A,C) = d(A,s) + d(s,t) + d(t,C) 10 s • As convenient as coordinate-based 2 1 20 systems A B C
  9. 9. Sequoia Tree for PlanetLab Latencies
  10. 10. Hierarchical Clustering for PlanetLab Nodes in Europe Spain and Portugal UK and Ireland Scandinavia
  11. 11. Summary • Virtual Trees to Model Internet Path Metrics • Predict Bandwidth and Latency • Convenient ‘‘Coordinates’’ • Hierarchical Clustering http://research.microsoft.com/research/sv/sequoia

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