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ContextContext--aware Migratory Servicesaware Migratory Servicesin Ad Hoc Networks*in Ad Hoc Networks*
Rutgers-Helsinki Ph.D. Student Workshop onSpontaneous Networking
8-12th May 2006
Oriana RivaUniversity of Helsinki, Dep. of Computer Science
*Joint work with Liviu Iftode (Rutgers), Cristian Borcea (NJIT)and Tamer Nadeem (Univ. of Maryland)
Connecting to Internet throughConnecting to Internet throughad hoc networksad hoc networks
Internet
How else can we exploit theHow else can we exploit thead hoc networkad hoc networkcharacteristics to support acharacteristics to support anew class of applications?new class of applications?
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Ad hoc networks as service providersAd hoc networks as service providers
ü Enable a new class of services specific toubiquitous computing environments
üü AAcquire, process, disseminate real-timeinformation
ü Targets: region, activity, entity
Traffic Information from region at constantTraffic Information from region at constantdistance in front of the driverdistance in front of the driver
ü Requirements:• Service must be aware of its context• Service must adapt to user’s context
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Entity Tracking ServiceEntity Tracking Service
ü Requirements:• Service must be aware of its target• Service must preserve its execution state over time
Spontaneous Monitoring ServiceSpontaneous Monitoring Service
ü Requirements• Transfer code from node to node• The service must be aware of its context
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Requirements for services in ad hocRequirements for services in ad hocnetworksnetworks
ü Context-awareness• dynamism of services and request targets
ü User-driven adaptability• dynamism of user needs and operational context
ü Service continuity• due to context changes a node may become incapable
of hosting the service any longer• need to support stateful interaction
ü On-demand code distribution• nodes do not possess the code for any type of service
OutlineOutline
ü Motivations
ü Context-aware Migratory Services
ü Migratory Services Framework
ü Evaluation
ü Conclusions & Future Works
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Migratoryservice
end-point
Migratory Services ModelMigratory Services ModelMS migration
Virtual client-service interactionPhysical client-service interaction
Clientend-point n1
C n3
MSState
n4
n5
MSState
MSState
Migratoryservice
end-point
Migratory Services ModelMigratory Services Model -- contcont’’dd
Clientend-point n1
C
Meta-service
n2
SMigratory service
MSState
n3
MSState
n4
n5
MSState
MSState
ü One-to-onemapping betweenclients andmigratory services
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Example: Region monitoring ServiceExample: Region monitoring Service
Request
Migration
n1
C
MS
Response
n3
n4
MS Exit
Migration
Migration
n3
n1
Cn2
S
n5n5
Response
MS n4
MS
MS
Key ideas in Migratory ServicesKey ideas in Migratory Services
ü Capable of migrating to different nodes in thenetwork in order to effectively accomplish theirfunction
ü 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 migratedü Service migration is triggered by context changesü Service migration is transparent to the client
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OutlineOutline
ü Motivations
ü Context-aware Migratory Services
ü Migratory Services Framework
ü Evaluation
ü Conclusions & Future Works
Migratory Services FrameworkMigratory Services Framework
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Migratory Service ImplementationMigratory Service Implementationusing Smart Messagesusing Smart Messages
ü Smart Messages• implemented on a modified version of Sun’s Java K
Virtual Machine
ü 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 ManagerContext Manager
ü Context data provided by the SM platform• location, time, speed using GPS• device status information
• neighbors list
ü MonitoredCxt identifiers are translated into SMI/O tags
ü Access to context data by polling or blocking oncorresponding SM tags
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Context Rules andContext Rules and ValidatorValidator
ü Evaluate if a service computation can be“correctly” carried out on the current hosting node
ü If not, trigger migrationü CxtRules are service/client-specific policies
• inCxtRules – control on incoming data• outCxtRules – control on outgoing data
ü 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 ManagerCommunication Manager
ü Tasks:• Discover meta-services• Route messages between communicating end-points• Carry out service migration
ü Use naming conventions defined by SMü Two basic SM routing algorithms:
• geographical routing (similar to GPSR)• region-bound content-based routing (similar to
AODV)
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Reliability ManagerReliability Manager
ü Fault-tolerance to onefailure
ü Inactive version of theservice on a secondarynode
ü In case of failure of theprimary version, thesecondary version cantake over the serviceprovisioning
ResponseResponse
Update
Update
Update
ResponseResponseResponseResponse
ActiveService
InactiveServiceClient
Timeout
Request
ResponseDelete
ResponseResponse
primarynode
secondarynode
OutlineOutline
ü Motivations
ü Context-aware Migratory Services
ü Migratory Services Framework
ü Evaluation
ü Conclusions & Future Works
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Prototype Migratory Service:Prototype Migratory Service: TJamTJam
ü Predict traffic jams inreal-time
ü Traffic jams arelocally congestedphases in which carstravel at slow or zerovelocity
ü TJam utilizes twotypes of informationthat every car owns:• number of one-hop
neighboring cars• speed of one-hop
neighboring cars
num numnumber number
num num
speed speedspeed speed
speed speed
tjam number speed
jamtjam tjam
total
avg - minP = maxP ×max - min
avg - maxP = maxP ×min - max
P' = × P +(1- )× PNP = P' ×N
α α
TJamTJam:: TestbedTestbed ExperimentsExperiments
üü Ad hoc mobile network ofAd hoc mobile network of11 HP iPAQs with 802.1111 HP iPAQs with 802.11cards and GPScards and GPS
üü Use mobility tracesUse mobility tracesüü 11--2 hops communication2 hops communicationüü 2/3 neighbors2/3 neighbors
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TJamTJam constantly executes in the userconstantly executes in the user--specified regionspecified region
0
400
800
1200
1600
2000
2400
2800
3200
3600
0 50 100 150 200 250 300 350 400
time (sec)
Loca
tion
(m)
user locationservice location/correct answerservice location/wrong answerupdatesuser range
TJamTJam: Simulations: Simulationsü ns-2 simulator with the CMU-wireless extensionsü microscopic traffic generator tool Micro-VTGü Goal: Investigate the scalability of migratory
services in large scale networksü Study based on the comparison of
• TJam-Smart: migratory service model implementation• TJam-Base: baseline centralized approach
ü Metrics• inter-response time• correct response generation time• packet utilization rate• response packets overhead
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Simulations: effects of number of clientsSimulations: effects of number of clientsü highway of length 25km with 3 lanesü vehicles avg speed is 30m/s with a gap of 150mü 800 vehicles (500 vehicles active and 50 service
nodes)
0
0,01
0,02
0,03
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0,05
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0,07
50 100 150 200 250 300
Clients number
Cor
rect
resp
onse
gene
ratio
n tim
e (s
ec)
0
0,5
1
1,5
2
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3
3,5
Inte
r-res
pons
e tim
e (s
ec)
Correct response generation time (Smart) Correct response generation time (Base)Inter-response time (Smart) Inter-response time (Base)
Simulations: effects of vehicles speedSimulations: effects of vehicles speed
0
0,01
0,02
0,03
0,04
0,05
0,06
10 20 30Vehicles speed (meter/sec)
Cor
rect
resp
onse
gene
ratio
n tim
e (s
ec)
0
0,5
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2
2,5
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Inte
r-res
pons
e tim
e (s
ec)
Correct response generation time (Smart) Correct response generation time (Base)Inter-response time (Smart) Inter-response time (Base)
ü 150 clients
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OutlineOutline
ü Motivations
ü Context-aware Migratory Services
ü Migratory Services Framework
ü Evaluation
ü Conclusions & Future Works
ConclusionsConclusions
ü Migratory Services enables a new class ofservices in ad hoc networks• services quickly adapt to changes in the physical
environment, in the node capabilities, and networktopology
• service continuity to the clientü Experimental results demonstrate the feasibility
of our approachü Simulation results demonstrate the scalability
and efficiency of migratory services compared toa traditional centralized approach
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Future WorksFuture Works
ü Extend migratory services to smart phonesusing Portable Smart Messages (J2ME CDC)
ü Experimental testbed of nokia 9500
ü Use migratory services to collect contextinformation of entities and environments• Integration with the Contory middleware
• Contory is a middleware for the provisioning ofcontext information on smart phones
Thank you!
