CMPSEM027 Online Gaming

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CMPSEM027Online Gaming

• Abdennour El Rhalibi

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AIMS

• This module will explore the various design,
  technical and interactivity issues involved in
  multiplayer games.
• By understanding these issues, developers can
  identify the factors that affect them, and learn
  which architecture, techniques and methods to use
  in online games design and implementation.

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Learning Outcomes

• This course will show current techniques in
  online game design. After completing the module
  the student should be able to
• Explain design issues involved in online gaming
• Defines interactivity thoroughly as it relates to
  online games and other media productions
• Addresses the technical design and implementation
  issues involved in online games
• Explains how to use interactivity in online game
  design and how to use it as a critical evaluation
  tool

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What this course mainly covered?

• NOT about game design, graphic design and game
  programming.
• Mainly emphasis on Network Programming in support
  network game deployment
• How network performance, scalability and security
  issues associate with network game development?

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Content

• Lecture 1 Aspects of Network Games, TCP/IP
  Fundamentals, Internet Services and Application
  Layer Protocol, DirectPlay Overview, Online Games
  Issues
• Lecture 2 Network Game Design Fundamentals
• Lecture 3 DirectPlay (1)
• Lecture 4 DirectPlay (2)
• Lecture 5 Internet-based Database Systems
• Lecture 6 Concurrent/Multi-Threading Programming
  in Client/Server Software
• Lecture 7 Socket Programming (1)
• Lecture 8 Socket Programming (2)
• Lecture 9 Massively Multiplayer Games Design and
  Issues and Solutions Implementation
• Lecture 10 11 The Fundamentals and Issues of
  Mobile Games Mobile Game Development
• Lecture 12 Advanced Topics about Online Gaming

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Assessment

• 1 Coursework 40 Literature survey of recent
  publications, and writing-up an essay on online
  gaming issues.
• 2 Coursework 60 group work covers Programming
  Project involving online gaming design,
  architecture and algorithms.

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References

• Alex Jarett, and the IGDA Online Games Committee
  (2002) IGDA Online Games White Paper available
  from IGDA website at http//www.igda.org/online_r
  eport.htm.
• Mark DeLoura, (2000) Game Programming Gems",
  (Ed.) Charles River Media,
• Markus Friedl, (2002), Online Game Interactivity
  Theory. Charles River Media. ISBN
  1-58450-215-0.
• Andrew Mulholland, and Teijo Hakal, (2001)
  Developer's Guide to Multiplayer Games  
  Wordware Publishing, Inc ISBN 1556228686
• Todd Barron and LostLogic (2002) Multiplayer
  Game Programming
• Premier Press Game Development series, ISBN
  0-7615-3298-6
• Crooks, Clayton, Ii, (2001) 3D Game Programming
  With Direct X 8.0. Trade Paper, ISBN 1584500867
• Mark Deloura (2001) Game Programming Gems II,
  (Ed.) Charles River Media, ISBN 1584500549.
• Alan Watt and Fabio Policarpo, (2001) "3D Games
  Real-time Rendering and Software Technology,
  Volume 1", Addison-Welsey, ISBN 0201619210.
• Online Game Interactivity Theory (ISBN
  1-58450-215-0)
• Developing Online Games (ISBN 1-5927-3000-0)
• Core Techniques and Algorithms in Game
  Programming (ISBN 0-13-102009-9)
• Website for tutorial and examples D9 SDK
  msdn.microsoft.com/archive/en-us/
  directx9_c/directx/play/

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Aspects of Networking inMultiplayer Computer
Games
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What is Network game?

• Online game
• using TCP/IP or UDP/IP or proprietary network
  protocols
• LAN based network game
• Peer-to-Peer approach
• Massively Multi-Player game
• Client/Server approach
• Mobile Games
• can be download from the Internet and
  multi-played by using bluetooth or infrared or
  through the mobile phone network (e.g. GSM and
  3G)

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Massively Multiplayer Games (MMG)

• Examples
• Lineage, EverQuest
• 2M players
• 180K concurrent players
• Characteristics
• Large number of shared objects

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Abstraction of a Multiplayer Game

• What is a massively multiplayer game besides the
  story and 3D graphics?
• A distributed application
• Sharing part of the data
• Both reading and updating shared data
• Real-time
• Number of clients can be large
• Clients are heterogeneous
• How Can a client obtain the shared data?

Shared Data and Data from other user
Local Data
Each local computer continuously gets and updates
both data to support user interaction
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MMOG Server Model
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Communication Architectures
Split-screen Console - Limited players

• All peers equal
• Easy to extend
• Doesnt scale (LAN only)

Server pool -Improved scalability -More complex

• One node server
• Clients only to server
• Server may be bottleneck

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Client-Server v.s. Peer-to-Peer

• Client-Server Model of Massively Multiplayer games

• Peer-to-Peer System

Clients (peers) communicate without a centralized
server. Shared state are distributed to each
client
Clients gets shared data from server and
communicate with others using the server
Server Keeps all shared information and
coordinate communication among users

• Inexpensive
• Not Scalable (but improving)
• No single-point failure

• Expensive
• Scalable
• Single-point failure

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The Internet

• The Internet is a global web of interconnected
  computers and computer networks.
• The architecture that describes how systems on
  the Internet communicate with each other is known
  as the Internet architecture, also referred to as
  the TCP/IP architecture.

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ISO/OSI 7-Layer Reference Model(International
Organization for Standardization / Open Systems
Interconnection)
Sender
Receiver
The ISO/OSI RM was defined by the ISO in 1977.
Application
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Network
Data Link
Data Link
Data Link
Physical
Physical
Physical
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ISO/OSI 7-Layer Reference Model Cont.)

• Each layer of the ISO/OSI reference model is
  described here
• PL is responsible for the physical communication
  between entities, it carries raw bits between
  devices.
• DLL adds framing and reliability to the raw bit
  stream that is sent between physical layers.
• NL routes data between different data links.
• TL takes data from the session layer and divides
  it into smaller units, which are then passed to
  the NL.
• SL managers the process-to-process communication
  sessions between hosts.
• PreL controls how data is represented, e.g. ASCII
  to EBCDIC conversion and encryption.
• AL provides end-user services. Users typically
  interact with these layer, e.g. e-mail program
  and FTP program.

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The Internet Protocol (IP)

• The IP is defined by RFC791 standard which
  provides the most basic level of services in the
  Internet - routing a datagram.
• Given a bit of data, a packet and an IP address,
  IP tries to route the packet through the network
  until it reaches its destination.
• IP is a connectionless protocol.
• IP may lose the packet somewhere in the network.
• IP packet may also be corrupted during routing.
• IP does not guarantee that the packets will be
  arrived in sequence.
• As a conclusion, IP makes a best effort delivery.
  It does not promise that everything will go
  well.
• To compensate for IPs shortcomings, the Internet
  architecture use two transport protocols, TCP and
  UDP.

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IP address

• One of the key parameters given to IP along with
  a packet of data is the destination address for
  the packet.
• IP addresses are 32-bit quantities and composite
  with the Network and Host portions.
• Network portion of the address is used to route a
  packet to the individual network that contains
  host.
• Host portion of the address indicates the unique
  computer in the Internet.
• A computer can have more than one IP addresses,
  but one IP address must belong to one unique
  computer at any moment.
• IP address is a logical address which can be
  dynamic assigned.
• IP address can represent in two format, binary
  and dotted decimal notation.

Binary notation Dotted decimal notation
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Transmission Control Protocol (TCP)

• TCP is a connection-oriented protocol.
• TCP connection is reliable, bi-directional.
• TCP provides the following services
• guaranteed delivery of data
• error detection and recovery
• data delivered in sequence
• no duplicated data
• management of a session/service established
  between the source and destination system

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User Datagram Protocol (UDP)

• UDP is designed for lightweight application
  messaging.
• UDP is connectionless and unidirectional
  protocol.
• UDP provide data detection but no data correction
  and data retransmission.
• When an error is discovered, a UDP datagram is
  simply thrown away.
• If IP loses a UDP datagram on the way to the
  destination, UDP does not detect that it was lost.

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DirectPlay
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DirectPlay

• Introduction to DirectPlay
• Features
• Services
• Protocol
• Whats New in DirectPlay for DirectX 9

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DirectPlay8 ConfigurationsGaming Topologies

• Client-Server
• Dungeon Siege (Gas Powered Games)
• Giants (Planet Moon Studios)
• JumpGate (NetDevil)
• Peer-peer
• Sacrifice (Shiny Entertainment)
• MechWarrior4 (Microsoft)
• GameVoice (Microsoft)

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DirectPlay8 Client-Server

• Clients do not know of other clients
• All sends routed via the server
• Server must be capable of handling several
  clients
• Suitable for large games with many players
• Massively Multiplayer Games

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DirectPlay8 Peer-Peer

• Players are connected to all other players
• Sends may targeted at other players directly
• Host migration (Managed for you)
• Suitable for small(er) numbers of players

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DirectPlay8 API

• Easy to use and understand
• Deterministic behavior
• Logical message order
• Matched messages
• Create \ Destroy matching handled automatically
• Groups
• Send to Multiple targets efficiently

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DirectPlay8 API

• Powerful
• Asynchronous operations
• Overlapped I/O
• Application payloads when connecting and
  enumerating sessions
• Player context values

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DirectPlay8 API

• Flexible
• Select ports
• Multiple service providers / adapters / ports
• Asynchronous or synchronous operations
• Send parameters
• Reject connections
• Ignore enumerations
• Scalability parameters
• Push model

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Push Model

• Messages are pushed to the application via
  call-back function
• Thread pool
• Multithreaded
• Scalable
• A pull (polling) model can be implemented if
  required

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DirectPlay8 Architecture
Application
API Calls
Call-backs
DirectPlay8
API / Core
Transport Protocol
IPX SP
Modem SP
Serial SP
IPv6 SP
IPv4 SP
SP Service Provider
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DirectPlay8 Core

• Implements API
• Performs callbacks to applications message
  handler function
• Performs name table management
• Co-ordinates service provider usage
• Provides integration with DirectPlay8Voice and
  DirectPlay8Lobby

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DirectPlay8 CoreHost Migration

• Host migration for peer-peer sessions
• Deterministic host election based on connect
  order
• Guaranteed transactions
• No session fragmentation

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DirectPlay8 Protocol

• Service provider agnostic
• Guaranteed / non-guaranteed and sequential /
  non-sequential messages
• Based on UDP when over IP
• Automatic send throttling
• Send timeouts
• Low overhead

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DirectPlay8 Service Providers

• Several provided
• IPv4
• IPX
• Modem
• Serial
• New
• IPv6
• Bluetooth (Pocket PC)

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DirectPlay8 Reliability

• DirectPlay8 is a complete rewrite
• Robust error recovery
• Edge conditions
• Large number of clients, heavy network traffic
• Deterministic behavior
• Connecting, disconnecting, host migrating
• Well Tested

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DirectPlay8 Scalability

• Written to scale
• Multithreaded to support multiple processors
• Tested with several thousand clients
• Optimal and suboptimal conditions

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Whats New in DirectPlay ?DirectPlay for DirectX
9

• DirectX 9 keeps the DirectPlay 8 Interfaces
• NAT/Firewall traversal support
• Most NATs and firewalls for client-server
• Windows ME and XP for peer-peer

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Whats New in DirectPlay ?

• Exposed Thread Pool Interface
• You decide how many threads Direct Play will use
• Allows thread priority modifications
• Thread start/shutdown notification
• Create a data pool for each thread to work with

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Whats New in DirectPlay ?

• Pocket PC Support
• No DirectPlay Voice support
• Bluetooth support
• IPv6 added to Direct Play 9
• Determines availability
• Assists with NAT traversal
• Falls back to IPv4
• Direct Play Protocol Tuning Enhancements
• Tunable Parameters
• Packet Throttling
• Automatic send throttling

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Why use DirectPlay8 ?

• Great platform for networked games
• Robust
• Scalable
• DirectPlay makes networking easier
• Service provider agnostic
• Services like voice and lobby
• Handles NAT for you
• Leverage work and resources