15-213 Research Overview Talk Odyssey - 1

Imagine you are a tourist in Paris
 with a wearable computer
 wireless access to remote services
 unobtrusive heads-up display, microphone, earphones
 speech for computer interactions
 online language translation
Let’s go . . . . . .
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Lack of hardware?
NO!
We have what we need.
Lack of applications?
Nope - we have those too.
Need a system capable of coping with the problems of mobility
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Mobile elements are resource-poor
 relative to static elements of same era
 weight, power, size constraints
Mobility leads to communication uncertainty
 enormous variation in bandwidth & latency
 intermittent connectivity
Power management is a concern
 actions may have to be slowed or deferred
 communication costs energy need to rely on resources of remote servers, but may not be able to reach them!
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Make mobile clients more robust by offering adaptation
 rely on servers when possible
 function autonomously if needed
 monitor and adjust to current conditions
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applications consume resources network bandwidth, CPU cycles, battery power, disk space, $$$ resources are variable
…so… applications adapt use of resources as resource quality changes
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Support variety of applications and data types
Concurrent applications
Quick adaptation
Simple programming model
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The Operating System?
Individual applications?
Both!
15-213 Research Overview Talk
… Application-Aware Adaptation
Odyssey - 8

Where work gets done let powerful remote servers do the work
How snazzy the data is: “Fidelity” degrade data meaningfully before giving to mobile host has many dimensions
 one is universal: consistency
 others depend on data type movies: frame rate, frame quality geographical databases: feature set, minimum feature size
 tradeoffs are application-dependent
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We built a prototype runs on several UN*X platforms logically an OS extension provides a small API to applications
Implementation follows directly from the high-level design need data type aware components to offer fidelity choices need a central piece to watch the resources (network, etc.)
15-213 Research Overview Talk Odyssey - 10

System-level data differentiation through wardens
 specialized code components (a la device drivers)
 provides system-level support to manage a data type
 trusted entities (unlike applications)
Wardens subordinate to viceroy
 single, central component
 type-independent, system-level support
 responsible for all resource allocation, arbitration
 central point of authority and control for Odyssey
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Upcall
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Applications give viceroy a window of tolerance for some resource
 viceroy monitors resource availability
 if it leaves window, notifies application via upcall
Fid. 1 Fid. 2 Fid. 3 Fid. 4
Available bandwidth
Our architecture supports many resources
 we currently focus only on network bandwidth
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Video server offers movie at several levels of fidelity application plays the track that the current bandwidth can support xanim: split into client and server
WWW
“distillation server” degrades data before shipping to client images can be compressed
HTML can be summarized
Netscape: client-side proxy + remote distillation server
Speech Recognition local/remote/hybrid execution
Janus: support remote recognition method, hybrid
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Application-aware adaptation is superior to static strategies applications are able to attain desired “performance”
 movie doesn’t drop frames
 web delays are masked by compression
 speech recognition always available
Centralized resource management outperforms alternatives all applications come closer to meeting performance goals
Agility needs improvement
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Short term
 adaptation for Web objects other than images
 improving agility on bandwidth drops
 support for unified cache managment
Medium term
 explore integration of Odyssey in other operating systems
 broaden number of managed resources
 enlarge range of supported applications
 ...
Long term
 deploy Odyssey for real use
 dynamic function vs. data shipping as in speech
 ...
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Need for adaptation in mobile systems is widely recognized
Application-aware adaptation
 offers most general and effective approach to adaptation
 collaborative partnership between system and application
 previous approaches are limiting cases of this approach
15-213 Research Overview Talk
Odyssey prototype provides initial validation of concept
Odyssey - 17

Primary contributors
 Jason Flinn
 Dushyanth Narayanan
 Brian Noble
 M. Satyanarayanan
 Eric Tilton
 Kip Walker
Numerous secondary contributors involved in
 Coda
 Janus
 NetBSD
 Trace Modulation
 etc., etc., etc.
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