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Multimedia Services based on Mobile Agent

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

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Multimedia Services based on Mobile Agent

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  1. 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

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

  3. 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

  4. 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

  5. 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

  6. Survey of Agent Environments • Agent 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. Distributed Multimedia Service System • The agent structure • transport header • agent header • agent script

  14. Agent Structure • AG-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

  15. Agent Structure • Name • name of the file in agent load • Size • size of the file in agent load • Load length • indicates the total number of files in the agent load

  16. 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

  17. 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

  18. 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

  19. Multimedia Server Infrastructure(3)

  20. Multimedia Server Infrastructure(5) • Working Principle • Agent startup and configuration phase 1. connect to multimedia server 2. request to start an agent 3. Server redirect request to MAP 4. MAP initializes and starts an agent • Agent service phase 1. communicate with other agent 2. migrate to other multimedia servers to access their multimedia data

  21. Agent Startup

  22. MAP Architecture(1) • Five components: • Agent Execution Environment • Migration Facilitator • QoS & multimedia module • Service Location Module • Agent Communication Module

  23. 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

  24. Migration Facilitator(1) • Agent Tcl 2.0 daemon listens to port 6138 • Transport 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

  25. 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

  26. Migration Facilitator(3)

  27. 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

  28. 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

  29. Agent Communication Module • Get the AG-ID from the service agent • Make a connection

  30. 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

  31. Audio Decoder • deciphers the encoded bitstream • restores the quantized values • reconstruct the audio signal

  32. 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’; }

  33. Transmission Plan

  34. Buffer Management in Client Side • use a leaky bucket model to keep the bit rate of audio data at 128kbps • consists of a finite queue • when a packet arrives, append it at the end of queue if buffer is available • otherwise, discards the packet • at every clock tick, one packet is transmitted to decoder

  35. Leaky Bucket Model

  36. 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

  37. 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

  38. Future Work • Finish the implementation of MAP • Try to protect the multimedia server against malicious agent • Try to protect agent against malicious host

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