Context- -aware Migratory Services aware Migratory Services - - PDF document

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Context- -aware Migratory Services aware Migratory Services - - PDF document

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Context- -aware Migratory Services aware Migratory Services Context in Ad Hoc Networks* in Ad Hoc Networks* Rutgers-Helsinki Ph.D. Student Workshop on Spontaneous Networking 8-12th May 2006 Oriana Riva University of Helsinki, Dep. of

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Context Context-

  • aware Migratory Services

aware Migratory Services in Ad Hoc Networks* in Ad Hoc Networks*

Rutgers-Helsinki Ph.D. Student Workshop on Spontaneous Networking 8-12th May 2006

Oriana Riva University of Helsinki, Dep. of Computer Science

  • riana.riva@cs.helsinki.fi

*Joint work with Liviu Iftode (Rutgers), Cristian Borcea (NJIT) and Tamer Nadeem (Univ. of Maryland)

Connecting to Internet through Connecting to Internet through ad hoc networks ad hoc networks

Internet

How else can we exploit the How else can we exploit the ad hoc network ad hoc network characteristics to support a characteristics to support a new class of applications? new class of applications?

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Ad hoc networks as service providers Ad hoc networks as service providers

Enable a new class of services specific to

ubiquitous computing environments

  • A

Acquire, process, disseminate real-time information

Targets: region, activity, entity

Traffic Information from region at constant Traffic Information from region at constant distance in front of the driver distance in front of the driver

Requirements:

  • Service must be aware of its context
  • Service must adapt to user’s context
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Entity Tracking Service Entity Tracking Service

Requirements:

  • Service must be aware of its target
  • Service must preserve its execution state over time

Spontaneous Monitoring Service Spontaneous Monitoring Service

Requirements

  • Transfer code from node to node
  • The service must be aware of its context
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Requirements for services in ad hoc Requirements for services in ad hoc networks networks

Context-awareness

  • dynamism of services and request targets

User-driven adaptability

  • dynamism of user needs and operational context

Service continuity

  • due to context changes a node may become incapable
  • f hosting the service any longer
  • need to support stateful interaction

On-demand code distribution

  • nodes do not possess the code for any type of service

Outline Outline

Motivations Context-aware Migratory Services Migratory Services Framework Evaluation Conclusions & Future Works

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5 Migratory service end-point

Migratory Services Model Migratory Services Model

MS migration Virtual client-service interaction Physical client-service interaction

Client end-point n1 C n3 MS

State

n4 n5 MS

State

MS

State

Migratory service end-point

Migratory Services Model Migratory Services Model -

  • cont

cont’ ’d d

Client end-point n1 C Meta-service n2 S Migratory service MS

State

n3 MS

State

n4 n5 MS

State

MS

State

One-to-one

mapping between clients and migratory services

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Example: Region monitoring Service Example: Region monitoring Service

Request Migration

n1 C MS

Response

n3 n4 MS

Exit Migration Migration

n3 n1 C n2 S n5 n5

Response

MS n4 MS MS

Key ideas in Migratory Services Key ideas in Migratory Services

Capable of migrating to different nodes in the

network in order to effectively accomplish their function

3 basic mechanisms:

  • Monitor the context of interacting entities
  • Specify in context rules how the service execution is

context-dependent

  • Migrate the service from node to node and resume its

execution once migrated

Service migration is triggered by context changes Service migration is transparent to the client

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Outline Outline

Motivations Context-aware Migratory Services Migratory Services Framework Evaluation Conclusions & Future Works

Migratory Services Framework Migratory Services Framework

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Migratory Service Implementation Migratory Service Implementation using Smart Messages using Smart Messages

Smart Messages

  • implemented on a modified version of Sun’s Java K

Virtual Machine

Migratory Services

  • clients, migratory services, and meta-services are

Java programs that register with the framework

  • the framework maps these programs onto lower-

level SMs

  • SM self-routes using geographical and content-

based routing

Context Manager Context Manager

Context data provided by the SM platform

  • location, time, speed using GPS
  • device status information
  • neighbors list

MonitoredCxt identifiers are translated into SM

I/O tags

Access to context data by polling or blocking on

corresponding SM tags

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Context Rules and Context Rules and Validator Validator

Evaluate if a service computation can be

“correctly” carried out on the current hosting node

If not, trigger migration CxtRules are service/client-specific policies

  • inCxtRules – control on incoming data
  • outCxtRules – control on outgoing data

CtxRules are condition/action statements

  • Conditions are full binary trees of Boolean expressions

(comparisonNodes + combinationNodes)

  • Ex: < OR, <batteryLevel, EQUAL, low>,

<responseLocation, OUT_REGION, userRegion> >

  • Actions: migrate service, send update, accept/refuse

response,...

Communication Manager Communication Manager

Tasks:

  • Discover meta-services
  • Route messages between communicating end-points
  • Carry out service migration

Use naming conventions defined by SM Two basic SM routing algorithms:

  • geographical routing (similar to GPSR)
  • region-bound content-based routing (similar to

AODV)

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Reliability Manager Reliability Manager

Fault-tolerance to one

failure

Inactive version of the

service on a secondary node

In case of failure of the

primary version, the secondary version can take over the service provisioning

Response Response Update Update Update Response Response Response Response Active Service Inactive Service Client

Timeout

Request Response Delete Response Response

primary node secondary node

Outline Outline

Motivations Context-aware Migratory Services Migratory Services Framework Evaluation Conclusions & Future Works

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Prototype Migratory Service: Prototype Migratory Service: TJam TJam

  • Predict traffic jams in

real-time

  • Traffic jams are

locally congested phases in which cars travel at slow or zero velocity

  • TJam utilizes two

types of information that every car owns:

  • number of one-hop

neighboring cars

  • speed of one-hop

neighboring cars

num num number number num num speed speed speed speed speed speed tjam number speed jam tjam tjam total

avg

  • min

P = maxP × max

  • min

avg

  • max

P = maxP × min

  • max

P' = × P +(1- )× P N P = P' × N α α

TJam TJam: : Testbed Testbed Experiments Experiments

  • Ad hoc mobile network of

Ad hoc mobile network of 11 HP iPAQs with 802.11 11 HP iPAQs with 802.11 cards and GPS cards and GPS

  • Use mobility traces

Use mobility traces

  • 1

1-

  • 2 hops communication

2 hops communication

  • 2/3 neighbors

2/3 neighbors

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TJam TJam constantly executes in the user constantly executes in the user-

  • specified region

specified region

400 800 1200 1600 2000 2400 2800 3200 3600 50 100 150 200 250 300 350 400

time (sec) Location (m) user location service location/correct answer service location/wrong answer updates user range

TJam TJam: Simulations : Simulations

ns-2 simulator with the CMU-wireless extensions microscopic traffic generator tool Micro-VTG Goal: Investigate the scalability of migratory

services in large scale networks

Study based on the comparison of

  • TJam-Smart: migratory service model implementation
  • TJam-Base: baseline centralized approach

Metrics

  • inter-response time
  • correct response generation time
  • packet utilization rate
  • response packets overhead
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Simulations: effects of number of clients Simulations: effects of number of clients

highway of length 25km with 3 lanes vehicles avg speed is 30m/s with a gap of 150m 800 vehicles (500 vehicles active and 50 service

nodes)

0,01 0,02 0,03 0,04 0,05 0,06 0,07 50 100 150 200 250 300

Clients number Correct response generation time (sec)

0,5 1 1,5 2 2,5 3 3,5

Inter-response time (sec)

Correct response generation time (Smart) Correct response generation time (Base) Inter-response time (Smart) Inter-response time (Base)

Simulations: effects of vehicles speed Simulations: effects of vehicles speed

0,01 0,02 0,03 0,04 0,05 0,06 10 20 30

Vehicles speed (meter/sec) Correct response generation time (sec)

0,5 1 1,5 2 2,5 3

Inter-response time (sec)

Correct response generation time (Smart) Correct response generation time (Base) Inter-response time (Smart) Inter-response time (Base)

150 clients

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Outline Outline

Motivations Context-aware Migratory Services Migratory Services Framework Evaluation Conclusions & Future Works

Conclusions Conclusions

Migratory Services enables a new class of

services in ad hoc networks

  • services quickly adapt to changes in the physical

environment, in the node capabilities, and network topology

  • service continuity to the client

Experimental results demonstrate the feasibility

  • f our approach

Simulation results demonstrate the scalability

and efficiency of migratory services compared to a traditional centralized approach

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Future Works Future Works

Extend migratory services to smart phones

using Portable Smart Messages (J2ME CDC)

Experimental testbed of nokia 9500 Use migratory services to collect context

information of entities and environments

  • Integration with the Contory middleware
  • Contory is a middleware for the provisioning of

context information on smart phones

  • riana.riva@cs.helsinki.fi

Thank you!