1© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, The Role of Cloudlets in Mobile Computing Mahadev Satyanarayanan School of Computer Science Carnegie Mellon University

2© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, Based on same Spanish test set BLEU SCORES Systran Spanish Google Chinese (06 NIST) CBMT Spanish 0.3 Google Arabic (05 NIST) SDL Spanish Google Spanish 08 top lang Human Scoring Range Machine Translation Today

3© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, Face Recognition Today

4© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, Whats 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© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, Latency Hurts Even If Bandwidth Good (E.g. QuakeViz interactive benchmark on VNC thin client 100 Mbps)

6© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, Sample Internet2 RTTs (milliseconds)

7© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, 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© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, Solution: Create a Tiny Cloud Nearby Low-latency high-bandwidth 1-hop wireless network Olympus Mobile Eye Trek Wearable Computer Handtalk Wearable Glove Nokia N810 Tablet Android Phone Coffee shop Cloudlet WAN to distant cloud on Internet cloudlet = (compute cluster + wireless access point + wired Internet access + no battery limitations) data center in a box

9© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, 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 n 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 Mbps, but 16 2 Mbps

10© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, Cloudlet vs. Cloud CloudletCloud StateOnly soft stateHard and soft state ManagementAppliance model: self-managed; little professional attention Utility model: professionally administered, 24x7 operator coverage EnvironmentData center in a box at customer premises Machine room with power conditioning and cooling OwnershipDecentralized ownership by local business Centralized ownership by Amazon,Yahoo!, etc. NetworkLAN latency and bandwidth Internet latency and bandwidth SharingFew users at a time100s to 1000s of users

11© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, 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 inherent tension

12© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, 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© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, Dynamic VM Synthesis MobileDeviceMobileDevice CloudletCloudlet Preload base VM Discover & negotiate use of cloudlet private VM overlay (base + overlay) launch VM Execute launch VM Create VM residue VM residue Finish use done Depart Discard VM Optional: cache VM overlay Use cloudlet user-driven device-VM interactions

14© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, Typical Overlay Sizes (base VM = 8GB Ubuntu Linux) ApplicationCompressed VM Overlay Size (MB) Uncompressed VM Overlay Size (MB) Install Package Size (MB) AbiWord GIMP Gnumeric Kpresenter PathFind SnapFind Null

15© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, VM Synthesis Time at 100Mbps (untuned proof-of-concept prototype) Nearly half the total All in the infrastructure Potentially optimizable

16© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, When Bandwidth Drops to 10Mbps

17© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, 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© M. SatyanarayananMicrosoft Networking Research Summit, Bellevue, WA, In Closing (but keep the Swiss Army Knife handy for emergencies) Leverage the Cloud! VM-based CLoudlets