Introduction to Multiplayer Network Technology

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Introduction toMultiplayer Network Technology

• Thomas Lidy

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Introduction

• Networking - used in ...
• e-commerce
• training education
• distributed engineering design
• entertainment
• multi player games
• ? networked virtual environments

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Networked Virtual Environment

• software system
• multiple users interact in real-time
• shared sense of space and time
• realistic 3D graphics and sound
• a way to communicate
• interaction with the virtual environment

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Networked Virtual Environment

• components
• graphics engines and displays
• communication and control devices
• processing systems
• data network

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Origins of virtual environments

• origins in military (and industry)
• academic research in networked virtual
  environments
• virtual worlds on PC class systems- 3D games

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Origins in military

• SIMNET
• started 1983
• developed for DARPA
• DIS (protocol)
• defined after 1989
• standardized packets (PDUs)
• distributed heterogeneous

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Origins in industry

• SGI - Flight (1984)
• SGI - Dogfight (1985)

Academic origins
Flight

• NPSNET (1986)
• PARADISE (1993)
• BrickNet (1991)

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Origins on PC class machines

• Doom (1993)
• Macintosh
• Marathon (1994)
• Bolo (tank game)

Doom

• ... and many others

Bolo
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Network Technology

• Issues for networking
• Latency
• time required from one host to another
• Bandwidth
• data rate how many bits per second
• Reliability
• how much data is lost

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Sockets and Ports

• allow multiple applications to use the network

Applications ftp www netVEs games
port s protocols IP layer
IP (Internet Protocol)
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Internet Protocol (IP)

• low-level protocol
• basic services
• splits reassembles packets
• TTL field (time to live)
• other protocols lie on top of IP

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Transmission Control Protocol (TCP)

• layered on top of IP (? TCP/IP)
• simple point-to-point connection
• automatic acknowledgments
• error checking
• correct packet order
• ?reliability

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User Datagram Protocol (UDP)

• also layered on top of IP
• connectionless
• packet-by-packet basis
• best-efforts delivery (not reliable)
• less processing time ? faster
• deal with packet loss and ordering!

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IP Broadcasting

• instead of sending multiple copiesof a packet to
  all destinations
• single transmission to all hosts in the network
• broadcasting to address 255.255.255.255
• disadvantages
• expensive for hosts that are not interested
• delivery only on LAN - not Internet-wide!

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IP Multicasting

• receiver-controlled distribution
• interested hosts subscribe to a list
• packets are sent down distribution paths
• no burdens for hosts not interested
• less overhead than broadcasting
• appropriate for Internet use

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Multicast routing
New York
Moscow
Washington
London
Tokyo
Denver
Prague
Munich
Vienna
Graz
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IP Multicasting

• addressing
• pseudo IP (class D address)range 224.0.0.0 -
  239.255.255.255
• can be used temporarily or reserved by IANA
• problems
• routers must be multicast-capable
• not yet available troughout the Internet
• ?multicast routers communicate directly with each
  other through the MBONE

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Overview (1)
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Overview (2)
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Networking today - Conclusion

• networkingessential part of multi player
  environments
• designers must carefully selectprotocols and
  network archtitecture
• multicasting most efficient technique for
  large-scale netVEs
• games today use client/server, peer-to-peer
• multicasting probably becomes more globally
  available with IPv6

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The End

• Thomas Lidy