1© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
The Role of Cloudlets in Mobile Computing
Mahadev Satyanarayanan
School of Computer Science
Carnegie Mellon University
2© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
Based on same Spanish test set
0.4
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BL
EU
SC
OR
ES
SystranSpanish
GoogleChinese
(‘06 NIST)
CBMTSpanish
0.3GoogleArabic
(‘05 NIST)
0.3859
0.5137
0.5551 0.5610
SDLSpanish
0.85
0.7447
GoogleSpanish
’08 top lang
0.7289
Human Scoring Range
Machine Translation Today
3© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
Face Recognition Today
4© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
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© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
Latency Hurts Even If Bandwidth Good(E.g. QuakeViz interactive benchmark on VNC thin client 100 Mbps)
6© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
Sample Internet2 RTTs (milliseconds)
7© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
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© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
Solution: Create a Tiny Cloud Nearby
Low-latencyhigh-bandwidth1-hop wireless
network
Olympus Mobile Eye Trek
Wearable Computer
HandtalkWearable
Glove
Nokia N810Tablet
AndroidPhone
Coffee shopCloudlet
WAN todistant cloudon Internet
cloudlet = (compute cluster+ wireless access point+ wired Internet access+ no battery limitations)
““data center in a box”data center in a box”
9© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
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 bwe.g. 802.11n ≈ 400 Mbps but HSPDA ≈ 2 Mbps
• shipping large objects within interactive time boundse.g. captured images in an augmented reality system
4MB JPEG image takes 80 ms @ 400 Mbps, but 16 seconds @ 2 Mbps
10© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
Cloudlet vs. Cloud
CloudletCloudlet CloudCloud
State Only soft state Hard and soft state
Management Appliance model:
self-managed; little
professional attention
Utility model:professionally administered, 24x7 operator coverage
Environment “Data center in a box” at customer premises
Machine room with power conditioning and cooling
Ownership Decentralized ownership by local business
Centralized ownership by Amazon,Yahoo!, etc.
Network LAN latency and bandwidth
Internet latency and bandwidth
Sharing Few users at a time 100s to 1000s of users
11© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
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 valueinherent tension
12© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
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© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
Dynamic VM Synthesis
Mobile
Device
Cloudlet
Preload base VM
Discover & negotiateuse of cloudlet
private VM overlay (base + overlay) launch VM
Execute launch VM
Create VM residue
VM residue
Finish usedone
Depart Discard VM
Optional: cache VM overlay
Usecloudlet
user-drivendevice-VM
interactions
14© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
Typical Overlay Sizes(base VM = 8GB Ubuntu Linux)
Application Compressed VM Overlay Size (MB)
Uncompressed VM Overlay Size (MB)
Install Package Size (MB)
AbiWord 119.5 364.2 10.0
GIMP 141.0 404.7 16.0
Gnumeric 165.3 519.8 16.0
Kpresenter 149.4 426.8 9.1
PathFind 196.6 437.0 36.8
SnapFind 63.7 222.0 8.8
Null 5.9 24.8 0.0
15© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
VM Synthesis Time at 100Mbps(untuned proof-of-concept prototype)
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20
40
60
80
100
120
140
AbiWord GIMP Gnumeric Kpresenter PathFind SnapFind Null
Tim
e in
Sec
on
ds
Other
Resume VM
Apply VM overlay
Decompress VM overlay
Transfer floppy disk
Compress floppy disk
Transfer VM overlay
Largest standard deviation is 5.3% of mean
Nearly half the totalAll in the infrastructurePotentially optimizable
16© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
When Bandwidth Drops to 10Mbps
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AbiWord GIMP Gnumeric Kpresenter PathFind SnapFind Null
Tim
e in
Sec
on
ds
Other
Resume VM
Apply VM overlay
Decompress VM overlay
Transfer floppy disk
Compress floppy disk
Transfer VM overlay
Largest standard deviation is 3.4% of mean
17© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
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© 2009-2010 M. Satyanarayanan Microsoft Networking Research Summit, Bellevue, WA, 2010-06-02
In Closing
(but keep the Swiss Army Knife handy for emergencies) Leverage the Cloud!Leverage the Cloud!
VM-based CLoudlets