ECOOP'99 PhDOOS 1

A Framework for Dynamically Configurable Multimedia

Distribution

Fabio Kon and Roy H. Campbell

Department of Computer ScienceUniversity of Illinois at Urbana-Champaign

http://choices.cs.uiuc.edu

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Introduction

Multimedia interfaces are becoming increasingly important.

Future systems will abandon dull interfaces based on text and still images.

Video, audio, and animations will prevail.TV and Radio broadcasting systems will

join the network.

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Problems with Multimedia Streaming Technology

Existing MBone and unicast solutions do not provide good levels of

Control Flexibility Scalability Quality of Service Management

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Previous Work

Object-Oriented Multimedia Distribution System in C++ [KCT+98].

Multimedia Reflectors work as relays.Network of Reflectors can be remotely:

reconfigured monitored

Decentralized administration.

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A Reflector Network

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The Multimedia Reflector

Applications: Live Multimedia Streaming Stored Content Streaming Audio/Videoconference

Multiple ChannelsMultiple Input and Output

connections

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Data Distribution Protocols

C++ abstract class Connection: open(); close(); Bind(); Connect(); Send(); Receive();

Bandwidth Control

Subclasses: UDPConnection TCPConnection MulticastConnection

Most of Reflector’s code deals only with the abstract class.

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Experimentation(First Round)

Live video from NASA’s Pathfinder Mission

3 months> 30 reflectors in 5 continents> 1 million video sessionsJava Applet decoding 24kbps of

H.263 video GSM audio

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Problems Encountered

1. Code update:Bug fixes and new versions.

i. Manually FTP new code to host machineii. Telnet to host machine

a. Shutdown existing versionb. Start new version

Repeat this dozens of times

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Problems Encountered

2. Dynamic Reconfiguration Channels, in/out connections, max # of

clients. Configuration information was kept in a

centralized location.A. Update the configuration database.B. Connect to each Reflector and instruct it

to download the new configuration. Tiresome and error prone.

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Problems Encountered

3. Fault-ToleranceSupported with redundant streams

Extreme waste of bandwidth.

Solution: Use Infrastructure offered by

dynamicTAO, a dynamically configurable CORBA ORB.

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Solution

Wrap the Reflector with a CORBA IDL interface.

dynamicTAO, CORBA ORB extended with a reconfiguration meta-interface to allow:1. Uploading executable code.2. Dynamically load components into the runtime.3. Change configuration parameters of applications.4. Modify internal structure of component-based apps.

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Reconfiguration Agents

SysAdmins use a GUI to build agents for reconfiguration inspection

GUI is used to1. Build distribution

graph2. Select reconfiguration

and inspection commands

3. Visualize results.

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Reconfiguration Agents

Code uploading example:

upload_impl Connection UDPCon

load_impl Connection UDPCon

hook_impl >Connection Reflector UDPConnection

Reconfiguration example:

configure_impl Reflector “MAX_NUM_CLIENTS=200”

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Fault-Tolerance

Goal: maximize availability without relying on redundant data transmission.

Solution: The Reflector maintains a list of alternate

inputs for each of its channels. If a Reflector dies, first it tries to inform its

neighbors. Input silent for too long switch to another

one.

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Representing Inter-Component Dependence

ComponentConfigurator frameworkImplementations in C++, Java, and CORBA

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Implementation StatusCompleted

Non-CORBA version of the Reflector dynamicTAO and infrastructure for

reconfiguration agentsWorking on

CORBA wrapper for the Reflector Breaking Reflector code into

dynamically loadable components Fault-tolerance with the help of the ComponentConfigurator Framework

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Future Work

Automatic Management of data flows to minimize user delays optimize network utilization support load balancing

Integrate with CORBA Naming and Trading Services

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Related Work

White Pine’s Multipoint Control Unit for Meeting Point (proprietary protocols for reconfiguration, no code updates).

Our system can be seen as an extension to the idea of the MBone, or a set of tools for managing MBone

broadcasts.

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Conclusions

Internet Multimedia Distribution Systems will replace existing Radio and TV networks.

But first, they must provide high levels of flexibility, configurability, and scalability.

Our design builds on OO Frameworks, CORBA, mobile agents, and dependence representation.

Not limited to Multimedia.These methods can be applied in any large,

distributed component-based system.

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For More Information...

dynamicTAO web site:

http://choices.cs.uiuc.edu/2K/dynamicTAO

ComponentConfigurator source code and documentation:http://choices.cs.uiuc.edu/2K/ComponentConfigurator

E-Mail: f-kon@cs.uiuc.edu