Quazal Eterna Multiplayer Connectivity

1
Quazal EternaMultiplayer Connectivity

• Irwin Chiu Hau
• Computer Science
• McGill University
• Winter 2004

2
Overview

• Introduction
• What is Eterna?
• Duplication Spaces
• Powerful Features
• Important Features
• Conclusion

3
Introduction

• Internet came into existence
• Network games gained popularity
• MMP online games is getting bigger and bigger
• Hundreds of players
• Thousands of players
• Millions of players ????
• Achieving this is not easy task
• Problems arise

4
Internet Problems

• Unreliability
• High Latencies
• Bandwidth Limitation
• Resource Constraints
• Traditional message passing becomes inefficient

5
Developers Expectations

• Developers need good solutions
• Low cost
• Low risk
• High value alternative
• Quazal comes up with a product that meets
  developers expectations
• This commercial product is called ETERNA

6
Eterna

• Significantly reduce the costs associated with
• Developing a MMP game
• Time Expense
• Running a MMP game
• Bandwidth
• Maintenance

7
Eterna

• Featuring hybrid approach
• Peer-to-peer and Client-Server Communications
• Decentralizes game information to maximize
• Reliability
• Scalability
• Performance
• Security

8
Powerful Features

• Duplication Spaces
• Dead-Reckoning
• Load Balancing
• Hierarchical Updates
• Cross Platform
• Etc
• ? High performance, reliable MMP games that will
  satisfy even the most demanding game players.

9
Important Features

• Flexibility
• Security
• System fault tolerance
• High performance, reliable MMP games that will
  satisfy even the most demanding game players.

10
Duplication Spaces

• Introduction
• Technology Overview
• All About Duplication Spaces
• Conclusion

11
Introduction

• Duplication Spaces
• Eternas underlying technology
• Eternas essential component

12
Technology Overview

• Quazals Philosophy
• Based on three fundamental concepts
• High-Level abstraction
• Descriptive approach
• Distributed object structure

13
Duplication Spaces

• What is a Duplication Space?
• How to Declare a Duplication Space
• Publish-Subscribe Model
• Cells
• Multiple Duplication Spaces
• Scalability
• Communication Model

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What is a Duplication Space?

• It is a space where a duplicated object
• can discover or can be discovered by,
• another duplicated object
• It allows the developer to control
• where and how many duplicas of an object are
  published and when they are deleted

15
How to declare a Duplication Space?

• Data Definition Language ( DDL )
• based on classes
• Duplicated Object
• DataSet
• DupSpace

Compiled
DDL
C Classes
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Publish-Subscribe Model

• In a duplicated space, duplicated objects are
• Grouped together
• Related by a user-defined function (match
  policy)
• Assigned the role of
• subscriber
• publisher
• both

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Publish-Subscribe Model

• A subscriber is an object that can discover other
  objects within a duplication space
• A publisher is an object that can be discovered
  within a duplication space

Neverwinter nights Source http//nwn.bioware.com
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Subscribers Task

• A subscriber will discover the
• replica of a publisher on the station where the
  duplication master of the subscriber resides

Station 1 ( ?subscriber )
Station 2 (?publisher )
World of Warcraft Source http//www.blizzard.com
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Publishers Task

• A publisher will create a duplica of itself
• on the station where the duplication master
• of the subscriber resides

Station 1
Station 2
World of Warcraft Source http//www.blizzard.com
20
Match Policy

• Publishers and subscribers are related by a
• user-defined function called match policy

Conceptual diagram of a duplication space Source
Quazal Duplication Spaces
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Match Policy

• The PSMatch function determines whether or not
• A subscriber discovers a replica of the publisher
• An object should be discovered on a particular
  station
• The PSMatch compares each duplica of a publisher
  to each duplica of the subscriber

Conceptual diagram of a duplication space Source
Quazal Duplication Spaces
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Match Policy

• The PSMatch function is defined by the system
• The match condition
• Is defined by the developer
• Is the conditions under which the function will
  return
• true or false

Conceptual diagram of a duplication space Source
Quazal Duplication Spaces
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Match Condition

• If PSMatch returns true, then
• The publisher can be discovered
• The duplica of the publisher is created on the
  station where the duplication master of the
  subscriber resides
• The subscriber will discover the publisher object
• If PSMatch returns false
• The publisher cannot be discovered
• The duplica of the publisher will not be created
  nor will it be discovered by the subscriber

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Example
Illustration of the PSMatch mechanism Source
Quazal Duplication Spaces
P1 publisher P1 duplica of the publisher S2
subscriber S2 duplica of the
subscriber Station 3 acts like a server
PSMatch returns true ? Station 2 discovers
duplica of P1
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Cells

• Recap
• In the previous scenario, publisher-subscriber
  match computations are done on one station
• As the size of a session increases
• The number of computation increases
• To reduce the resource usage on a given station
• Distribute the processing of the match
  computation between many stations

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Cells

• Solution
• Divide the duplication space into CELLS
• Each cell
• Is responsible for a certain portion of the
  match computations

Duplication space with cells Source Quazal
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Cells

• The creation of CELLS enables the
• PSMatch computations to be distributed between
  stations participating in the session

Duplication space with cells Source Quazal
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Cell Match Function

• We need to determine if a particular duplicated
  object will be involved in a particular subtask
• This is defined by the CellMatch function
• CellMatch function determines
• If an object should be discovered in a cell

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CellMatch Condition

• Cell Match conditions are given by the developer
• For when the CellMatch function will return true
  of false
• If CellMatch returns true, then
• The duplica of the publisher or subscriber is
  created on the station where the duplication
  master of the cell resides
• After the CellMatch is performed
• PSMatch is performed on the publishers and
  subscriber where the duplication master of the
  cell resides

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Example
Illustration of the CellMatch mechanism Source
Quazal Duplication Spaces
C3 Cell C3 Duplica of Cell
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Duplicated Object Migration

• Eterna allows the control of Duplicated Objects
• Allows the duplication masters to migrate between
  stations
• Used in
• Fault tolerance
• Load balancing
• Eliminate the effect of latency

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Multiple Duplication Spaces

• It is possible to define several duplication
  spaces
• within a game
• Advantages
• Simplify implementation of PSMatch and CellMatch
• Easier to design the game
• Note
• Theres no restriction on how many duplication
  spaces an object may belong to

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Ex 3D Chat Room

• One DupSpace
• dataset
• location
• ZoneDescription
• RoomDescription
• dupspace RoomSpace
• doclass
• User / Participant / Observer
• Zone
• Room
• PSMatch
• returns true if users are in the same room

• dataset RoomDescription
• dohandle Zone
• string Name
• string Topic
• dupspace RoomSpace
• doclass User
• Location m_dsLoc
• subscriber in RoomSpace
• doclass Participant User
• publisher in RoomSpace

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Scalability

• Quazal Eterna Limitations
• 210, (1024) classes
• 222,(4 millions) duplication masters
• Hardware Limitations
• Memory
• CPU
• Network bandwidth

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Communication Model

• Eterna performs automatic message routing
• Eterna implements hierarchical and cascading
  message passing
• Multicast group objects are arranged in a
  tree-like configuration
• Distribute update messages without excessive
  bandwidth

Duplica information update
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End of Duplication Spaces
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Compensating for Latency and Bandwidth
Restrictions

• Dead-Reckoning ( Powerful Feature )
• Reduce the appearance of lag
• Local corrections
• Handle continuity breaks, such as walls and
  teleports
• Lookahead and loopback
• Predicts future events (on duplication masters)
• Etc, .

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Load Balancing

• Distribute workload
• Ensures workload correspond to station capacity
• Reduce bandwidth usage
• When user enters or leaves
• The workload distribution will change to optimize
  processing power and bandwidth

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Load Balancing

• Developers have complete control over how load
  balancing is performed in the game
• Any quantities can be load balanced by load
  balancing policies
• Load metrics
• CPU load
• Bandwidth usage
• Memory load
• Duplicated Objects
• Capacity metrics

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Flexibility

• Integrated middlewares
• 3D
• Physics
• AI
• Plug-ins to suit developers need
• Transport protocol
• Compression Encryption algorithms
• Still not satisfied?
• Our own plug-ins

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Flexibility

• Cross Platform

Source Square-Enix
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Security

• Security vs Performance
• Hybrid Peer to Peer / Client-Server architecture
• Client-Server
• Sensitive data login, password
• Key game variables
• P2P
• Less sensitive data can be sent directly between
  players
• High performance

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System Fault Tolerance

• Reliability
• By design, distributed systems are more reliable
  than client-server as there is no central point
  of failure
• If one station fails
• Fault tolerance allows a duplication master on
  the failed server to migrate to another station
• The game will continue seamlessly

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Conclusion

• Eterna seems powerful enough for building MMO
  games
• Eterna also seems reliable and secure
• Eterna provides flexibility to developers
• Does Eterna satisfies even the most demanding
• game players ?????

45
Questions?