Multimedia Services based on Mobile Agent

Presenter : Lee Chi Wai, Anson

Supervisors : Prof. Michael Lyu, Prof. Irwin King

Markers : Prof. Ng Kam Wing, Prof. Leung Ho Fung

Date : 28 Apr 2000

Outline of the presentation Introduction Survey of agent environments Distributed Multimedia Services System Agent based applications Conclusion Question and Answer Session

Introduction(1) Distributed multimedia services systems tend to be

heterogeneous The heterogeneous environments differ in

underlying hardware architecture Main problems:

Discovery of remote resources and services Configuration of the remote client or servers

Solutions: Scripting language can cover the heterogeneity of

environments

Introduction(2)Use of script:

Retrieve multimedia data in distributed environment

Create a common configuration between the communication parties

Reconfigure the systems which is already running

Mobile agent can provide flexibility to adapt themselves in heterogeneous environment

Introduction(3)Multimedia Transportable Agent System

Multimedia agent platform provides an agent transport protocol for agent

migration provides an agent communication environment

Multimedia applications retrieve multimedia data transfer of various audio or video data

Survey of Agent EnvironmentsAgent Tcl

support agents written in Tcl, Java, C and C++

agent server is multi-threaded each agent is executed in a separate

process agent communication uses inter-process

communication

D’Agents(Agent Tcl)Agent Tcl

agent server uses public-key cryptography to authenticate the identity of an incoming agent’s owner

resource manager agents assign access rights to agents based on authentication

enforcement modules enforce the access rights

Similarities and differences(1)Same general architecture:

a server on each machine accepts incoming agents

start up an execution environment for each incoming agent

load agent’s state information into the environment

resume agent execution

Similarities and differences(2)Multi-threaded servers and run each

agent in a thread of the server process itself

Multi-process servers and run each agent in a separate interpreter process

Similarities and differences(3) Nearly all mobile agent systems either

interpret their language directly Or compile their languages into bytecodes

and interpret the bytecodes Java is the most popular agent language

portable and efficient existing security mechanisms allow safe execution

of un-trusted code wide-spread market penetration

Similarities and differences(4)Two kinds of migration approach:

Captures agent object state, code and control state, allowing it to continue execution from the exact point at which it left off

Captures only agent object state and code, and restart execution on some known entry point inside its code

Similarities and differences(5) Protecting an individual machine against

malicious agents Do not provide any protection for the agent All systems are suitable for distributed

information retrieval Decision should be based on implementation

language, level of security and performance

Distributed Multimedia Service System

The agent structure transport header agent header agent script

A G - ID T yp e N a m e S izeL o a d

L e ngthA ge ntS ta te

M iss io nInfo

S e nd e r- ID R o uteInfo

A ge nt S c rip t

T ra nsp o rtH e a d e rA ge nt

H e a d e r

Agent StructureAG-ID

name the directory where the agent and the load are stored

used as a reference when an agent or any files is lost in the network

Type determines the type of the file distinguish between agent files and

different media files in agent load

Agent StructureName

name of the file in agent loadSize

size of the file in agent loadLoad length

indicates the total number of files in the agent load

Agent Header Sender Identification

user name, e-mail address Mission Information

describes the mission, parameter needed for the mission

Agent State stores number of sites already visited, type of

information found Route Info

a list of service site addresses that guide the agent during its mission

Multimedia Server Infrastructure(1) Implementation Language:

Agent Tcl/Tk, C System Specification:

Redhat Linux 6.2 Pentium II 333MHz w128MB RAM 4.3GB Harddisk

Tasks: Search and retrieval multimedia data based on title

matching Delivery multimedia data including audio and video to

end user

Multimedia Server Infrastructure(2) An extension module : the Multimedia Agent

Platform Starting, executing, accessing multimedia data

and management of agents Code of multimedia server doesn’t need to be

changed server doesn’t need to understand any MAP

related request any changes in MAP requests don’t affect the

server implementation

Multimedia Server Infrastructure(3)

A g e n t

A g e n tR e q u e s t

A g e n tR e s p o n s e

M u lt im e d iaS e rv e r

R e d ire c t

U s e rIn t e r fa c e

M A P

Multimedia Server Infrastructure(5) Working Principle

Agent startup and configuration phase1. connect to multimedia server2. request to start an agent3. Server redirect request to MAP4. MAP initializes and starts an agent

Agent service phase1. communicate with other agent 2. migrate to other multimedia servers to access

their multimedia data

Agent Startup

act iveA gent

G ETA gent

A gent sends it sG U I to user

M ult imediaServer

R edirect

U serInt erface

M A P

G et G U I

A gent G U I

C onfigurat ionInformat ion

MAP Architecture(1)Five components:

Agent Execution Environment Migration Facilitator QoS & multimedia module Service Location Module Agent Communication Module

MAP Architecture(2)Agent Execution Environment

Agent Tcl 2.0 interpreter recognizes the structure of the agent and

extracts information necessary to run the agent script

Agent scripts are written in Agent Tcl able to execute on any platform

Migration Facilitator(1)Agent Tcl 2.0 daemon listens to port

6138Transport of the agent and its load

For incoming agent:

1. read the agent header

2. create a directory in the agent data store

3. stores agent and load files

4. activates the Agent Execution Environment

5. waits for new incoming agent

Migration Facilitator(2) For departing agent:

1. it connects another migration facilitator in the destination machine

2. Transfers the agent file and all the files in the agent load

Migration Facilitator(3)

M ig ra tio n F a c ilita to r ( s e n d e r )

A g e n t d a ta s to re

In te rp re te r

N e tw o rk

A g e n ts c r ip t

M ig ra tio n F a c ilita to r (d e s tin a tio n )

A g e n t d a ta s to re

In te rp re te r

c a ll th e a g e n t_ ju m pc o m m a n d to m ig ra te toa n o th e r h o s t

In th e n e w h o s t, it w illr e s to re s th e s ta te o f th ea g e n t a n d c o n tin u e th ee x e c u tio n

QoS and Multimedia Module Problem in multimedia document delivery:

a media stream is continuous and of high bandwidth need

huge amount of data to transport Solution:

get feedback from the receiver, e.g. available buffer space, network bandwidth

modify or change the coding scheme to lower or raise the quality and bandwidth needs for the stream

Service Location Module Eliminates the need for a mobile agent to

travel to destination which doesn’t have the requested resources

Working principle:1. register itself with a service agent

2. supplies a set of attributes which describe the

service

3. get information about destination, such as next

hop address

Agent Communication ModuleGet the AG-ID from the service agentMake a connection

S e rv ic eA g e n t

A g e n t B

S e rv ic eA g e n t

A g e n t A

M u lt im e d ia A g e n tP la t fo rm

M a c h in e A M a c h in e B

1 ) re g is t e r A g e n t A

2 ) re q : w h e re is A g e n t A ?

3 ) re p : A g e n t A o n A

4 ) s e n d m e s s a g e s t o A g e n tA o n M a c h in e A

Agent Based Applications Audio Delivery

System Specification

Pentium II 333 MHz with 128M RAM

4.3GB harddisk Compression Algorithm

MPEG 1 layer III at 128kbps Layer III

most complex but offers the best audio quality bit rates around 64kbps per channel

Audio Decoder

deciphers the encoded bitstream restores the quantized values reconstruct the audio signal

B its tr e a mu n p a c k in g

F re q u e n c ys a m p le

re c o n s tru c tio n

F re q u e n c y totim e m a p p in g

Encodedbit s t ream

D ecodedP C Maudio

Transmission Plan

pseudo code :sleep interval t’=0.03125sec;

while (server buffer not empty){record the start time;transmit audio packet;record the stop time;sleep for t’ sec;compute next sleep interval t’;

}

t = 0s l ee p i n t e rv a l 1 s l ee p i n t e rv a l 2

t = 0 .0 3 1 2 5 s ec .

t = 0 .0 3 1 2 5 s ec . + t '

t ra n s mi t t h e fi rs tp a ck e t o f a u d i o d a t a

(5 1 2 b y t e s )

t ra n s mi t t h e s ec o n dp a ck e t o f a u d i o d a t a

(5 1 2 b y t e s )

t ra n s mi t t h e t h i rdp a ck e t o f a u d i o d a t a

(5 1 2 b y t e s )

Transmission Plan

128kbp s

bit s t ransferred(bit s )

s leep int erval

ideal t ransmiss ion p lan

Buffer Management in Client Side

use a leaky bucket model to keep the bit rate of audio data at 128kbps

consists of a finite queuewhen a packet arrives, append it at the

end of queue if buffer is availableotherwise, discards the packetat every clock tick, one packet is

transmitted to decoder

Leaky Bucket Model

N etw ork

t ime t

P acket U nregulat edflow

T he bucket holds p acket s

R egulat edflow

M P EG decoder

Video Delivery same system specification use MPEG 1 decoder from http://www.mpegtv

.com similar transmission plan as audio delivery,

differ in bit rate requirement (1.5Mbps in MPEG 1 standard)

can modify it to some advanced bandwidth smoothing algorithms

similar buffer management strategy as audio delivery

Conclusion Discuss similarities and differences of

different agent environments Propose to use mobile agent in searching and

retrieving multimedia data Discuss the system architecture and

prototype of multimedia server Present two multimedia data delivery

application build on the top of MAP

Future WorkFinish the implementation of MAPTry to protect the multimedia server

against malicious agentTry to protect agent against malicious

host