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The Role of Cloudlets in Mobile Computing

The Role of Cloudlets in Mobile Computing. Mahadev Satyanarayanan School of Computer Science Carnegie Mellon University. Machine Translation Today. 0.85. 0.8. Human Scoring Range. 0.7447. 0.7289. 0.7. 0.6. 0.5610. BLEU SCORES. 0.5551. 0.5137. 0.5. 0.4. 0.3859. 0.3. CBMT Spanish.

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The Role of Cloudlets in Mobile Computing

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  1. The Role of Cloudlets in Mobile Computing Mahadev SatyanarayananSchool of Computer ScienceCarnegie Mellon University

  2. Machine Translation Today 0.85 0.8 Human Scoring Range 0.7447 0.7289 0.7 0.6 0.5610 BLEU SCORES 0.5551 0.5137 0.5 0.4 0.3859 0.3 CBMT Spanish Google Chinese (‘06 NIST) Systran Spanish SDL Spanish Google Arabic (‘05 NIST) Google Spanish ’08 top lang Based on same Spanish test set

  3. Face Recognition Today

  4. What’s The Catch? • These are resource-intensive applications • State-of-art performance and quality only with room full of servers • How do we achieve this “in the wild”? • (on resource-poor, energy-limited mobile hardware) • Obvious solution: leverage the cloud! • But your cloud may be far away  • End-to-end latency matters for crisp interaction • e.g., real-time two-way language translation on mobile devices • e.g, augmented reality for cognitive assistance via “smart glasses” •  and many other examples

  5. Latency Hurts Even If Bandwidth Good(E.g. QuakeViz interactive benchmark on VNC thin client 100 Mbps)

  6. Sample Internet2 RTTs (milliseconds)

  7. Latency on 3G Networks • “The wireless delay in the 3G network dominates the whole network path delay, e.g., latency to the first pingable hop is around 200ms, which is close to the end-to-end Ping latency to landmark servers distributed across the U.S.” • from“Anatomizing Application Performance Differences on Smartphones”, to appear in MobiSys 2010 (Huang et al)

  8. AndroidPhone Nokia N810Tablet HandtalkWearableGlove Solution: Create a Tiny Cloud Nearby Olympus Mobile Eye TrekWearableComputer WAN todistant cloudon Internet Low-latencyhigh-bandwidth1-hop wirelessnetwork cloudlet =(compute cluster+ wireless access point+ wired Internet access+ no battery limitations) “data center in a box” Coffee shopCloudlet

  9. Local Wireless Bandwidth • Original motivation for cloudlets was latency • But 1-hop wireless bandwidth to cloudlet also a win • wireless LAN bw typically 100X wireless WAN bw • e.g. 802.11n ≈ 400 Mbps but HSPDA ≈ 2 Mbps • shipping large objects within interactive time bounds • e.g. captured images in an augmented reality system • 4MB JPEG image takes 80 ms @ 400 Mbps, but 16 seconds @ 2 Mbps

  10. Cloudlet vs. Cloud

  11. inherent tension Key Challenges • 1. Trusting infrastructure • tamper-resistant hardware (“first-world infrastructure”) • portable device as root of trust (e.g TrustSniffer) • 2. Finding the exactly right software on it uniformity  deployer value specificity  end-user value

  12. Transient Customization • Deliver fully configured virtual machine (VM) to infrastructure • Problem: too large, too slow for transient use • Solution: assemble VM on the fly  dynamic VM synthesis • prefetch large, relatively static, widely-used piece (“base VM”) • deliver small patch (“VM overlay”) just before use • discard VM after use • VM overlay can come from • mobile device over wireless link, or • web site under control of mobile device (URL and decryption key)

  13. private VM overlay user-drivendevice-VMinteractions Usecloudlet done VM residue Dynamic VM Synthesis Preload base VM Discover & negotiateuse of cloudlet Mobile D e vice Cloudlet (base + overlay)  launch VM Execute launch VM Finish use Create VM residue Discard VMOptional: cache VM overlay Depart

  14. Typical Overlay Sizes(base VM = 8GB Ubuntu Linux)

  15. Nearly half the totalAll in the infrastructurePotentially optimizable VM Synthesis Time at 100Mbps(untuned proof-of-concept prototype)

  16. When Bandwidth Drops to 10Mbps

  17. Some Education is Needed  • “In the discussion of the proposal, several members of the panel were skeptical about the argument about the need extremely low latencies for handheld devices. • In particular, handhelds are (historically) remarkably powerful computers capable of running user interfaces (the source of most latency sensitivity) locally. • The panel also felt that the case for "cloudlets" was not compelling in contrast to other distributed system architectures such as relying alarge-scale cloud based on conventional data centers and using a geographically distributed three-layer web service architecture.”

  18. In Closing  • Leverage the Cloud! • (but keep the Swiss Army Knife handy for emergencies) VM-based CLoudlets

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