Scalability of network environments Esau Libo and Damon Dept. of Computer Science University...

Scalability of network environments

Esau Libo and DamonEsau Libo and Damon Dept. of Computer ScienceDept. of Computer Science University College London University College London

Purpose of this seminar Describe the overall problem of scalability in virtual Describe the overall problem of scalability in virtual

environment and two approaches (MASSIVE & RING)environment and two approaches (MASSIVE & RING) in some detail. Discuss some applications.in some detail. Discuss some applications.

The overallproblem

ApproachesMASSIVE & RING

Discussion

Introduction

Introduction

ReviewComputers and networks strengthen an Computers and networks strengthen an Collaborative Virtual Environment (CVE)Collaborative Virtual Environment (CVE)

Computer have limitations and differing Computer have limitations and differing capabilitiescapabilities Network technologies like Ethernet, ATM and Network technologies like Ethernet, ATM and wirelesswireless

Each technology with bandwidth, delay Each technology with bandwidth, delay characteristics and reliability.characteristics and reliability.

Where we are

Approaches

Discussion

The overall problem

Scaling

Goals of CVE

Goals of CVEGoals of CVE

Introduction

ReviewSharing the use of information is the primary goal.Sharing the use of information is the primary goal.

Design to run over a set of heterogeneous Design to run over a set of heterogeneous computers and networks.computers and networks.

Maximise responsiveness and scalability while Maximise responsiveness and scalability while minimising latency (Roberts)minimising latency (Roberts)

Where we are

Approaches

Discussion

The overall problem

Scaling

Goals of CVE

ScalingScaling

Scaling

Introduction

ReviewScaling allows the amount of information in the Scaling allows the amount of information in the environment with number of users, to increase, environment with number of users, to increase, without reducing the fidelity of experience to any without reducing the fidelity of experience to any one user.one user.

Achieved by balancing each individuals need for Achieved by balancing each individuals need for information with what can be achieved.information with what can be achieved.

Where we are

Approaches

Discussion

The overall problem

Goals of CVE

Space structuring

Approaches

Discussion

The overall problem

。。。。。。。。。

Review

Space structuring

Division of virtual space

a) Separate Serversb) Uniform geometrical structurec) Free geometrical structured) User-centered dynamic structure

Where we are

Approaches

Discussion

The overall problem

。。。。。。。。。

Review

Network Topologies

Peer-to-peer UnicastPeer-to-peer MulticastClient/ServerMulti-Server Topology

Topologies

Space structuring

Where we are

Approaches

Discussion

The overall problem

。。。。。。。。。

Review

Definition of Scalability

Scalability

Space structuring

Topologic

Definition

…

…

• Scalability Scalability – How well a solution to some problem will How well a solution to some problem will

work when the size of the problem increases.work when the size of the problem increases.– For example…For example…complexity of O(N), O(N^2)complexity of O(N), O(N^2)

Where we are

Approaches

Discussion

The overall problem

。。。。。。。。。

Review

Scalability

Scalability

Space structuring

Topologic

…

…

Factors

Determining factors:

• graphical complexity • behavioral complexity• number of simultaneous participants

Where we are

Approaches

Discussion

The overall problem

。。。。。。。。。

Review

Scalability

Scalability

Space structuring

Topologic

…

…

Bottlenecks

Bottlenecks:

• Network Server• Dial-up Modems• PCs of users

Where we are

Approaches

Discussion

The overall problem

。。。。。。。。。

Review

Scalability

Scalability

Space structuring

Topologic

…

Solution:• limited information exchange

Example:• audio: objects too far away to hear• visual: objects behind the user

…

Solution

Where we are

Two approaches (MASSIVE & RING)

The overallproblem


Discussion

• facilitating scalabilityfacilitating scalability – it is based on the concept of aura.it is based on the concept of aura.

• controlling spatial interactioncontrolling spatial interaction – it deals with the control of interaction or it deals with the control of interaction or

communication between two objects once communication between two objects once they become aware of each other through they become aware of each other through aura collision .aura collision .

…

Spatial model

…

MASSIVE

Where we are

Discussion

The overallproblem ApproachesSpatial model of interaction

-major components

Key concepts: Key concepts: • medium medium : communication type: communication type• aura aura : subspace in which interaction can occur: subspace in which interaction can occur• awarenessawareness:: quantifies one object’s significance to another object (in a quantifies one object’s significance to another object (in a

particular medium) particular medium) • focus focus : represents an observing object’s interest: represents an observing object’s interest• nimbus nimbus : represents an observed object’s wish to be seen: represents an observed object’s wish to be seen• adapters adapters : can modify an object’s auras, focus, and nimbus : can modify an object’s auras, focus, and nimbus

Awareness and the Spatial Model of Interaction (1)

Where we are

Discussion

The overallproblem Approaches

…

Spatial model

…

MASSIVE

Awareness and the Spatial Model of Interaction (2)

Where we are

Discussion


…

Spatial model

…

MASSIVE

A example about watching TV

• implicitlyimplicitly through spatial actions such as through spatial actions such as moving and turning, e.g. when turning moving and turning, e.g. when turning around my focus and nimbus follow me, around my focus and nimbus follow me, resulting in an adjustment of my awareness resulting in an adjustment of my awareness of nearby objects of nearby objects

• ExplicitlyExplicitly by choosing from among by choosing from among different shapes and sizes, e.g. switching different shapes and sizes, e.g. switching between narrow or wide focus between narrow or wide focus

• via via adapter objectsadapter objects which transform which transform combinations of aura, focus and nimbus combinations of aura, focus and nimbus

Where we are

Discussion


…

Spatial model

…

MASSIVE

Spatial model of interaction- Three Three manipulationmanipulation ways ways

• MASSIVE MASSIVE is the “Model, Architecture and System for is the “Model, Architecture and System for Spatial Interaction in Virtual Environments”, an Spatial Interaction in Virtual Environments”, an experimental distributed virtual reality system intended to experimental distributed virtual reality system intended to support collaborative activity support collaborative activity

• It has been driven by key requirement:It has been driven by key requirement: Scale - supporting as many simultaneous users as possibleScale - supporting as many simultaneous users as possible

• It uses a spatial model of interactionIt uses a spatial model of interaction

Where we are

Discussion


…

MASSIVE

Functionality

…

MASSIVE functionality- IntroductionIntroduction

User-level featuresUser-level features• It is a multi-user distributed V.R. system. It is a multi-user distributed V.R. system. • There are textual, graphical and audio client programs There are textual, graphical and audio client programs

(usable in any combination) allowing users to communicate (usable in any combination) allowing users to communicate by graphical gestures, typed messages or real-time by graphical gestures, typed messages or real-time packetised audio. packetised audio.

• Text users may interact with graphical users and vice-versa. Text users may interact with graphical users and vice-versa. • All media are controlled by aura, focus and nimbus. All media are controlled by aura, focus and nimbus. • It includes adaptor objects (e.g. conference table, podium). It includes adaptor objects (e.g. conference table, podium). • There may be any number of worlds with portals to move There may be any number of worlds with portals to move

between worlds. between worlds. • Each process obtains and uses only (spatially) local Each process obtains and uses only (spatially) local

information. information.

• New media can be added without affecting the core system.New media can be added without affecting the core system. Where we are

Discussion


…

MASSIVE

Functionality

…

MASSIVE functionality- key feature for scalabilitykey feature for scalability (1)(1)

Lower-level featuresLower-level features• keyword-based interface trading for coordinating keyword-based interface trading for coordinating

client programs for different media. client programs for different media. • spatial interface trading based on aura collisions. spatial interface trading based on aura collisions. • medium-independent peer connections medium-independent peer connections

implementing focus, nimbus and awareness. implementing focus, nimbus and awareness. • integrated support for focus, nimbus and aura integrated support for focus, nimbus and aura

adaptors.adaptors.

MASSIVE functionality- key feature for scalabilitykey feature for scalability (2)(2)

Where we are

Discussion


…

MASSIVE

Functionality

…

MASSIVE functionality- A example of virtual conferenceA example of virtual conference

Graphics user’s interface Text user’s interface

The interactions in MASSIVE are a mixture of The interactions in MASSIVE are a mixture of client-server (between objects and the trader or client-server (between objects and the trader or aura manager) and peer-to-peer (between objectsaura manager) and peer-to-peer (between objectsin the world). Most of the interactions are in the world). Most of the interactions are bidirectional, being symmetrical in the case ofbidirectional, being symmetrical in the case ofpeer connections and involving asynchronouspeer connections and involving asynchronous notifications in the case of client server notifications in the case of client server connectionsconnections

Where we are

Discussion


MASSIVE

…

MASSIVE Architecture- IntroductionIntroduction

Architecture

…

• two conditionstwo conditions of interaction between of interaction between objects in the virtual world objects in the virtual world – compatible interfaces compatible interfaces – objects must become sufficiently proximate objects must become sufficiently proximate

as determined by their auras as determined by their auras

Where we are

Discussion

The overallproblem ApproachesMASSIVE Architecture

- Aura and spatial trading

MASSIVE

…

Architecture

…

Where we are

MASSIVE Architecture- how spatial trading operates Discussion


MASSIVE

…

Architecture

…

RING Architecture(1)

• RING represents a virtual RING represents a virtual environment as a set of independent environment as a set of independent entities each of which has a entities each of which has a geometric description and a behavior.geometric description and a behavior.

Where we are

Discussion


MASSIVE

Architecture

…

RING

……

…

…

• Entity:Entity: Multi-user interaction is supported Multi-user interaction is supported

by matching user actions to entity by matching user actions to entity updatesupdates

• Client-Server designClient-Server design Reliability, Redundancy, Load-Reliability, Redundancy, Load-

BalacingBalacing

Where we are

Discussion


MASSIVE

……

…


Architecture

…

RING

…

• Entity, Client, RINGEntity, Client, RING

• Every RING entity is Every RING entity is managed by exactly one managed by exactly one client workstationclient workstation

• Communication between Communication between clients is managed by serversclients is managed by servers

Where we are

Discussion


MASSIVE

RING

……

…


Architecture

…

…

RING Mechanism

• Message FilteringMessage Filtering Area of Interest (exploit communication locality)Area of Interest (exploit communication locality)

Regular subdivision (NPSNET), proximity (DIVE)Regular subdivision (NPSNET), proximity (DIVE) Pre-determined inter-cell occlusion (SPLINE)Pre-determined inter-cell occlusion (SPLINE) Visibility culling (RING)Visibility culling (RING)

Explicitly registering interest( NPSNET)Explicitly registering interest( NPSNET) Dead Reckoning (NPSNET, PARADISE) Dead Reckoning (NPSNET, PARADISE)

messages: O(Nmessages: O(N22) ) O(NP) O(NP)

• Network topology: IP-Multicast +Message Network topology: IP-Multicast +Message FilteringFiltering

Where we are

Discussion


MASSIVE

RING

……

…

Architecture

Character

…

Partition Regions(1)

Partition Regions(2)

RING Algorithm

• Changing "periodic" update Changing "periodic" update messages when entities cross cell messages when entities cross cell boundaries.boundaries.

• Using cell visibility "look-ups“Using cell visibility "look-ups“ Each cell Each cell a multicast group a multicast group Sends messages to its “cell”Sends messages to its “cell” Receive messages from its interest zone Receive messages from its interest zone

(including neighbouring cells)(including neighbouring cells)

Where we are

Discussion


MASSIVE

RING

……

…

Architecture

Character

…

Regions

VIE W PO INT

VIS IBLECELLS

INVIS IBLECELLS

Visibility Culling• Occlusion: indoor (rooms,buildings), outdoor(‘fog of war’)Occlusion: indoor (rooms,buildings), outdoor(‘fog of war’)• Visibility culling carried out with:Visibility culling carried out with:

– ‘‘Potentially visible sets’ of cells (pre-computed)Potentially visible sets’ of cells (pre-computed)– Temporal Bounding Volumes, Update Free RegionsTemporal Bounding Volumes, Update Free Regions

ClientServer

object A

object B

object C

viewpoint

Different RING systems

• 1. Peer to Peer 1. Peer to Peer O(NP), scale finitelyO(NP), scale finitely• 2. Client-Server ( single server, 2. Client-Server ( single server, staticstatic)) scale finitelyscale finitely• 3. Client-Server ( any server, 3. Client-Server ( any server, regionalregional)) scale infinitely scale infinitely region finite region finite• 4. Other systems4. Other systems

Where we are

Discussion


MASSIVE

……

…

…

RING

…

Compare

SystemSystemDesignDesign

Number Number of of

ServicesServices

ClientClient ServerServerInputInput OutputOutput InputInput OutputOutput

From From ServerServer

To To ServerServer

From From ClientClient

From From ServerServer

TotalTotal To To ClientClient

To To ServerServer

TotalTotal

StaticStatic(A)(A)

22 4.254.25 0.500.50 46.846.8 44.044.0 90.890.8 290.5290.5 44.044.0 334.5334.5

44 5.095.09 0.460.46 24.124.1 64.464.4 88.588.5 148.6148.6 64.764.7 213.3213.3

88 3.293.29 0.450.45 12.012.0 70.470.4 82.382.3 71.371.3 71.571.5 142.8142.8

1616 4.164.16 0.370.37 6.16.1 74.774.7 80.880.8 37.237.2 75.875.8 113.0113.0

RegionalRegional(B)(B)

22 4.674.67 0.420.42 48.248.2 1.91.9 50.250.2 270.7270.7 2.02.0 272.7272.7

44 3.893.89 0.530.53 24.224.2 4.34.3 28.528.5 153.0153.0 4.34.3 157.3157.3

88 4.154.15 0.460.46 12.312.3 3.63.6 15.815.8 83.583.5 3.63.6 87.187.1

1616 4.414.41 0.430.43 5.95.9 3.43.4 9.39.3 37.537.5 3.53.5 41.041.0

Table: Average message processing rates (messages per second)

Experimental results

• Static system design:Static system design:total number of server-server total number of server-server messages increases, sub-linearmessages increases, sub-linear

• Regional system design:Regional system design:inter-visibility decreaseinter-visibility decrease serverserver-server messaging reduceserver messaging reduce

Where we are

Discussion


MASSIVE

……

…

…

RING

…

Compare

Experimental Conclusion

• Different network characteristics and Different network characteristics and different system designs can different system designs can significantly affect the message significantly affect the message processing rates requiredprocessing rates required

• Hierarchical system (regional) scales Hierarchical system (regional) scales better than hierarchical system better than hierarchical system (static)(static)

Where we are

Discussion


MASSIVE

……

…

…

RING

…

Compare

RING system advantage

1. Less storage, processing, and 1. Less storage, processing, and network network bandwidth requirements;bandwidth requirements; very dynamic and complex message very dynamic and complex message

processing may processing may be performed by servers be performed by servers

2. High-level management2. High-level management

Where we are

Discussion


MASSIVE

……

…

…

RING

…

Compare

RING system disadvantage

1. Extra latency1. Extra latency

2. Currently support only visual 2. Currently support only visual interactions interactions

Discussion


MASSIVE

……

…

…

RING

…

Compare

Where we are

Discussion

The overallproblem


Discussion

Discussion• Multiplayer computer games Multiplayer computer games

Discussion


Quake includes a multi-player mode to play over LAN or the Internet with or against other humans. The network play uses a client/server model, where the actual game runs on the server only and all players "log in" there to participate. Depending on the client's specific route to the server, different clients will get different ping times. The lower your latency (ping time), the smoother your in-game motions, and the easier it is to accurately aim and score. Someone playing on the server PC gets a substantial advantage due to essentially zero lag

http://www.wordiq.com/definition/LAN

http://www.wordiq.com/definition/Internet

http://www.wordiq.com/definition/Client/server

http://www.wordiq.com/definition/Ping

http://www.wordiq.com/definition/Personal_computer

http://www.wordiq.com/definition/Lag

Discussion

• Will cyberspace as described by William Will cyberspace as described by William

Gibson or Neal Stephenson ever be builtGibson or Neal Stephenson ever be built

Discussion


Scalability of network environments Esau Libo and Damon Dept. of Computer Science University...

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