Architecture & Performance

Community Place case studyPresented by

u4068413Jin Hyung, SEO

Contents Introduction Architectural Possibilities Basic CP System Server Scalability Architectural features of current CP Performance Issue Distributed Architecture Conclusion

Introduction Aim : infrastructure that will allow many

users to participate in a shared, interactive 3D world

Large scale system capable of supporting many geographically dispersed users, interconnected through low bandwidth, high latency communication links

Possible System Architecture

Client–Server Architectures : simplest method of building a distributed system

Peer to Peer Systems : each client maintains a copy of data

Hybrid Systems : merge client-server and peer to peer model

CP System Architecture Ⅰ

Server Manager Dynamic data

WWW

browserCP browser

Client System (PC)

WWW

browserCP browser

Client System (PC)

WWW server (httpd)

Application Object (AO)VSAP

VSCP

VSCPHTTP

Basic CP Architecture

CP System Architecture Ⅱ Browser

Works in conjunction with a HTML browser Loads the 3D data file (in VRML 2.0 format) Contacts the server via the VSCP that runs above IP CP browser supports the VRML2.0 standard and uses

Java as its scripting language

Browser-server communicationVSCP (Virtual Society Communication Protocol) :

Efficient communication of 3D scene transformation Open-ended support for script specific message

CP System Architecture Ⅲ

Server Position tracker and message forwarder

Role : Manage the state of Object on behalf of

connected users Carry out a similar function for any script level

messages that are generated by a browser as a result of user interaction

Application Programming Models Ⅰ

SSS (Simple Shared Script) Model Small shared applications in the 3D world Master browser

AO (Application Object) Model More complicated application VSAP (Virtual Society Application Protocol) Dynamic addition of VRML data and associated

scripts to an existing scene Commercial environment

Application Programming Models Ⅱ

CP Browser

CP Browser

CP Browser

CP Browser

Server Aura Manager Dynamic data Server Aura

Manager Dynamic data

Simple Shared Script Application Object

4

11

223

3

4

5 55

6

6

Application

Object (AO)

Scaleability For scalability in large application….

Static scene data is downloaded initially as part of the VRML file while dynamic data can be managed using local scripts plus message passing

Offload some processing into the client browser using the local scripting facility

Sophisticated applications can be managed by external processes and can use the local script to manage local updates in individual browsers

Limit the number of messages needed between browsers

Spatial Areas of Interest

Area of application can be divided into several groups

Aura manager is responsible for defining groups of spatially co-located objects

Each objects in the same group are maintained consistent together

Feature of CP Architecture Total state of the shared VRML scene is

split between VRML data managed at the clients and data managed by the server since server is responsible for maintaining the location and some attribute data belong to client (ex> avatar data)

By pushing data out to clients : Reduce server load Increase performance

Server Performance Ⅰ

Sony workstation

Sun Sparc SGI Indigo2

Sony NEWS

Client

Server

Server Performance Experiment Environment

Server Performance Ⅱ CPU load with the number of connection

Sony and SGI are comparable and Sun 10% more powerful At 30% CPU idle time, Sony - 400 connections, SGI - 425

connections while Sun - 520 connections

Network Traffic Sony & SGI support a maximum 500 connections before

network performance tails off while Sun does almost 630 connection

AURASIZE & MAXINAURA Increasing the MAXINAURA will lead to a growth in traffic The interplay with the AURASIZE is less clear

Browser Performance Event processing cost within the browser

cost of this execution path is 0.99 ms (averaged over 3000 runs)

Cost of basic networking function average cost of 6.48 ms (repeated 3000

times)

Application message cost SSS model is more costly and sensitive to

server load

Distributed Architecture Ⅰ

WWW

browser

CP browser

Client System (PC)

Client System (PC)

Client System (PC)

WWW

browser

CP browser

WWW

browser

CP browser

User 1

User 2

User 3

VSCP

VSCP

VSCP

Multicast based

Group comms.

Replica of

Data item

Master copy

Of data item

Distributed Architecture Ⅱ Spatial model is used exactly as in

the single server case

It partitions the database into groups of spatially co-located objects who manage their consistency using a group communication model

Conclusion Most important goal of the CP project

has been to provide an infrastructure that allows easy creation of such spaces, within a familiar framework, the WWW

Scaling and performance issue should be always considered to support large numbers of users and more complicated scenes

Related Works

WWW and using full 3D shared space

Cybergate system (Blacksun Inc.) Moondo Pueblo Project (Chaco

Communication)

Q & A