Agile Application-Aware Adaptation for Mobility

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Agile Application-Aware Adaptation for Mobility
Odyssey

• Khaled Hadi
• ICS243F

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Outline

• The Need of Adaptation
• Taxonomy of Adaptation Strategies
• Goals of Odyssey
• Model Realization
• Design and Implementation
• Application Examples
• Conclusion

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The Need of Adaptation

• Poverty of resources
• Limited power
• Unpredicted network performance
• Inherently Insecure
• So, any viable approach to mobile computing must
  strike a balance between these competing
  concerns. This balance cannot be a static, mobile
  clients must be adaptive

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Taxonomy of Adaptation Strategies

• The range of strategies for adaptation is
  delimited by two extremes
• laissez-faire approach adaptation is entirely
  the responsibility of individual applications
• Application-transparent adaptation places entire
  responsibility for adaptation on the system.
• Between these two extremes lies a spectrum of
  possibilities that we collectively refer to as
  application-aware adaptation

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Taxonomy of Adaptation Strategies (Conts)

• Range of Adaptation Strategies

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Design Rationale

• Odyssey is a set of extensions to the NetBSD
  operating system to support adaptation for a
  broad range of mobile information access
  application

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Odyssey

• Odyssey is a mobile system capable of
• - Dynamic adaptation Change according to
• need
• - Agility Fast change

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Goals of Odyssey

• Fidelity The degree to which data presented at
  client matches the reference copy at the server
• Concurrency ability to execute multiple
  independent applications on a mobile client
  concurrently
• Agility detect and respond to change quickly
• Minimalism extended NetBSD

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Model Realization

• Viceroy
• - Mange resources
• - Type independent functionality
• Warden
• - type aware code components

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Model Realization (conts)

• The collaborative relationship envisioned in
  application-aware adaptation is thus realized in
  two parts
• - data-centric, between the viceroy and its
• wardens, it defines the fidelity levels for
  
• each data type and factors them into
• resource management
• -action-centric, between applications and
  Odyssey, it
• provides applications with control over the
  selection
• of fidelity levels supported by the wardens

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Design and Implementation

• An implementation of Odyssey must enable an
• application to
• Operate on Odyssey objects
• Express resource expectations
• Be notified when expectations are no longer met,
  and
• respond by changing fidelity

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Odyssey Client Architecture
Integrated into NetBSD New system call
included Odyssey implemented in User space
outside the kernel
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Expressing Resource Reservations
Application
Odyssey
Request
PARAMETERS Path Window Up-Call Resource-ID
Request-ID
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Notifying Resource Changes
Odyssey
Application
Up-Call
PARAMETERS Request-ID Resource-ID Resource-level
Tsop
Changing Fidelity
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Application Examples

• Video Player
• Web Browser
• Speech Recognizer

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Video Player (xanim)

• The server stores a number of tracks of the
  movie, each with a different fidelity
• Number of tracks, the size and offset of frames
  for each track is stored in meta data

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Web Browser (Netscape)

• The cellophane transforms the http request into
  file operations on odyssey web objects
• The web Warden is responsible for setting the
  fidelity level
• The distillation server provides multiple levels
  of fidelity

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Speech Recognizer

• Speech Warden is responsible for choosing to do a
  local, remote or hybrid (1st pass on client)
  recognition.
• Decision is dependent on available bandwidth

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Conclusion

• Partnership between application system
• Division of tasks
• Balance Performance and Fidelity