a middleware service for coordinated adaptation of communication services in groups of devices

A Middleware Service for Coordinated Adaptation of Communication Servicesin Groups of Devices

Fakultät Informatik, Institut für Systemarchitektur, Professeur Rechnernetze

Jordan Janeirojordan.janeiro@tu-dresden.de

Mobilis Project

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Agenda

• Motivation• Goals• Moratus• SACS• Evaluation• Future Work

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Motivation

• In ubiquitous computing, context information is important to execute dynamic adaptations• Bandwidth rate is considered as context (local

context)• Low transmission rates -> Better message

compression service• A device adaptation is based on ist context

• In a group communication, to assume the overall group context may be suitable• Collaborative applications

• Co-edition of Presentations

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Goals

• Determination of the overall group context• Global Context

• Adaptation of communication services in all group members

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Related Work

• Graceful Adaptation Protocol• Does not tolerante disconnection

• Ensemble• Not transparent adaptation

• NeCoMan• Does not tolerante disconnection• Pair-to-Pair Adaptation

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Moratus

• Protocol for coordinated service adaptation, among mobile group members, based on global context

• Communication services are called Message Transformation Services (MTS)• Optimize wireless group communication• Compression and segmentation• Divided in 2 modules:

• Encoder and Decoder

• Assumes a reliable group communication service• Jgroups

• Divide in 2 steps:• Global context election• Coordinated adaptation

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Global Context Election

• Any context variable might be used• RSSI in this case

• Starts upon a significant context variation• RSSI value ranges

• Different global context calculations might be implemented• Mean, lower value and highest value

• Handle device disconnection• Context of device is not considered

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Global Context Election

Variação significativa do contexto detectada !

Global

Context

Calculated

Global

Context

Calculated

Global

Context

Calculated

Global

Context

Calculated

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Global Context Election - Disconnection

Variação significativa do contexto detectada !

Global

Context

Calculated

Global

Context

Calculated

Global

Context

Calculated

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Coordinated Adaptation

• Divided in 4 steps to allow transparent adaptation:• Service installation• Activation of new decoder• Activation of new encoder• Deactivation of the old decoder

• One of the group devices coordinates the process

• Handle device disconnection

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Coordinated Adaptation

Group is

ready to

start the

adaptation

Install Service

Service

Instaled

Service

Instaled

Service

Instaled

Activate New

Decoder

New

Decoder

Activated

New

Decoder

Activated

New

Decoder

Activated

Coordinator

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Service for Coordinated Service Adaptation

• Used by distributed applications• Transparent communication

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Communication Service

• The use of Jgroups middleware• Proposes a protocol stack

• Allows reliable group communication• NACKACK protocol

• Disconnection handling• FAILURE_DETECTOR protocol

• Heartbeat message• Helps to refreshs list of group members

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Evaluation

• Scalability tests• Executed in a cluster with 30 machines• Groups of 5, 10, 15, 20, 25 and 30

elements

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Evaluation

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Conclusion

• Development of Moratus protocol• Adaptation based on the group context• Execution of coodinated adaptation

• Implementation of Moratus as a middleware service• Applications use the middleware transparently

• Limitations using Jgroups in wireless networks• Constant delays for protocol convergence

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Future Work

• Detect the consumption of all messages before concluding the coordinated adaptation

• Try to avoid consecutive and unnecessary adaptations

• Calculate global context considering multiple variables• Battery, bandwidth and processing

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Discussion

• Questions?

• Comments?

jordan.janeiro@tu-dresden.de