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

PLAN• I. Introduction

• II. Basis Model

• III. Agent System Architecture

• IV. Conclusion

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.