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An Architecture for a QoS-based Mobile Agent System. Mamadou Tadiou Kone and Tatsuo Nakajima Department of Information Science Japan Advanced Institute of Science and Technology. PLAN I.Introduction II. Basis Model III.Agent System Architecture IV. Conclusion. I.Introduction. - PowerPoint PPT Presentation
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Mamadou Tadiou Kone
and Tatsuo Nakajima
Department of Information Science
Japan Advanced Institute of Science and Technology
An Architecture for a QoS-based Mobile Agent System
I. IntroductionNature of Mobile Agents
A mobile Agent is an autonomous program that can halt itself,migrate with all its state from one machine to another and resumeexecution where it stopped.
Origin & evolution:
Client Server
Client Server
RPCMessage passing
REV (remote evaluation)
Parameters (data)
Results (data)
Procedure (code)
Results (data)
Client Server Active messageData and Code
Results (data)
Client Machine A
Server Machine C
Server Machine B
Network
RPC (remote procedure call) paradigm with a protocolversus
RP(remote programming) paradigm with its language.
Server
Agent (code, data
and context)
Server
A new approach to Client/Server communication
Client
The Concept of QoS (Quality of Service)
– QoS awareness:
Human perception : excellent, good, fair.
Application level : frame rate, sampling size, synchronization, distortion
System level : End to end delay (interactivity), delay jitter (synchro.) , Bit Error
Rate (BER), Package Error Rate (PER)
– QoS specification:
Players : Users, Application, Network, OSEntities : CPU, Network Bandwidth, Storage Capacity,
Memory Buffer, Peripherals (cards …)
II. Basis Model
System Components :
– The Virtual Host Interface
– The Virtual Host
– The Place
– The Resource Manager
System Components :
• The Place – Location where agents use services
– To provide adequate computation resources for the execution of an agent
• The Virtual Host Interface– Mapping user defined QoS onto System QoS
– Place configuration on request of the agent
– Keeping track of the agent movement
– Separation of QoS negotiation from resource management
The components :
• The Virtual Host– A virtual host is the location which manages a place
– It spans a set of physical hosts that have the resources refereed to in a given place
• The Resource Manager– A software component on a physical host
– It is in charge of resource reservation, allocation,
de-allocation on the physical host
– It interacts with the virtual host interface for granting resources to users
The virtual Host
Agent
TimelinessPrecisionAccuracy
ConsistencyPlace
Virtual Host
Physical Host
Physical Host
Physical Host
A client view of the System
Agent
TimelinessPrecisionAccuracy
Consistency
Virtual Host
Physical Host
Physical Host
Physical Host
TimelinessAccuracy
Consistency
PrecisionAccuracy
Consistency
Application
Virtual Host Interface
Heterogeneous Network Virtual Host Virtual Host
III. The Agent System Architecture
QoS assumptions
– Fixed number of QoS targeted : timeliness, accuracy, precision, consistency, availability.
– Necessary resources available
– Several types of QoS available at any place in a given virtual host
– Existence of a resource reservation scheme at the level of each physical machine.
– Case of multiple applications competing for same resources not considered.
Agent Movement / QoS negotiation processPhysical HostMobile Agent
Virtual Host InterfaceVirtual Host
Client Application
ResourceManager
QoS translationUser/System
QoS translationSystem/User
1. QoS satisfaction request
4. Local resourcereservation request
5. Local resourcecommitment
6. Available localresource granted
3. Local resourceallocation request
8. Available QoS satisfaction
2. SubjectiveQoS request
7. Available QoSgranted
QoS Adaptation
– Trade off between QoS types according to
client requests
– New resource insertion or resource failure handled transparently by the virtual host interface
– Failure recovery is managed by a simple checkpointing method
Inter-Agents Communication
Agent A at Place P1
Agent B at Place P2
Place P3
Target Placeredirectionif QoS not available
Agent Migrationif QoS availableQoS status
request &Response
IV. Conclusion• Summary:
A model of a QoS-based agent system is proposed to link QoS users and QoS providers.
The architecture relies on the distinction of QoS negotiation and resource management: the mobile agent system is in charge of the negotiation and the virtual host, of the management task.
Logical Disk Concept + Mobile Agent Technology
QoS control
improvement in QoS negotiation and management
• Issues : QoS adaptation, trade off, failure recovery.
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