Communication Architectures

1
Communication Architectures

• Chapter 4
• Eric Acosta

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Communication Architecture

• What is it?
• Method in which our workstations communicate
• Types of communication
• Logical communication
• The messages sent through the net-VE software
• Physical communication
• Wires between the workstations

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Why is it Important?

• Hardware chosen is a limiting factor on the
  number of players that can interact
• Message size and frequency dependent on hardware
  capabilities

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Scenario

• Utilize the Distributed Interactive Simulation
  (DIS) protocol data unit (PDU)
• Packets (contain state variables)
• 144 bytes long
• Simulation _at_ 30 PDU/s (frame rate)
• Players
• Aircraft 12 PDU/s
• Ground 5 PDU/s
• Humans 30 PDU/s
• Weapons 3 PDU/s

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Scenario Cont

• LAN 10Mbps (bandwidth)
• 1PDU 8bits/byte 144 bytes 1152 bits
• 10Mbps / 1152 bits/packet 8680 packets/s
• Player supported (assume use all bandwidth and
  CPU cycles)
• 8680 / (303) 263 humans firing a weapon
• 8680 / (123) 578 aircrafts firing a weapon
• 8680 / (53) 1085 ground firing a weapon

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Scenario Cont

• 56Kbps Modem (bandwidth)
• 1PDU 8bits/byte 144 bytes 1152 bits
• 56Kbps / 1152 bits/packet 48 packets/s
• Player supported (assume use all bandwidth and
  CPU cycles)
• 48 / (303) 1 human firing a weapon
• 48 / (123) 3 aircrafts firing a weapon
• 48 / (53) 6 ground firing a weapon

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Scenario Cont

• We might rethink packet size (or compression)
• Assume packet 22 of original (32 bytes)
• 1PDU 8bits/byte 32 bytes 256 bits
• 56Kbps / 256 bits/packet 218 packets/s
• Player supported (assume use all bandwidth and
  CPU cycles)
• 218 / (303) 7 humans firing a weapon
• 218 / (123) 14 aircrafts firing a weapon
• 218 / (53) 22 ground firing a weapon
• Table 4-1 pg.93 (Technology comparisons)

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Two Players on a LAN
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Two Players on a LAN

• Description
• Each player communicates directly via a LAN
• Advantages
• Reliable, ordered packets
• Disadvantages
• Only have two players
• When to use
• Only have two players

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Multiplayer client-server
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Multiplayer client-server

• Description
• Players send/receive packets via a server
• Advantages
• Can reduce message traffic to individual players
  by selectively sending messages
• Compress multiple packets into one
• Slow down bursty packets for smoother packet rate
• Server is configured to communicate with players
  reliably with out the overhead of a fully
  connected
• net-VE
• Disadvantages
• Server becomes the bottleneck
• When to use
• Preferred if administrator task required (e.g.,
  expensive computations that clients can not
  handle)

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Multiplayer Client-Server With Multiple Servers
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Multiplayer Client-Server With Multiple Servers

• Description
• Server serving a number of players
• Can connect server-to-server (10Mbps or 100Mbps
  or higher)
• Can connect player-to-server
• Advantages
• Provides scalability by allowing designers to
  scale beyond the CPU limits of a single server
  Disadvantages
• Servers become bottlenecks
• Need high speed connections
• When to use
• When scalability is an issue
• Have high speed connections
• Need administration task(s)

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Peer-to-Peer on a LAN
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Peer-to-Peer on a LAN

• Description
• Communication is player-to-player(s)
• Advantages
• Reaches limit of number of players slower than a
  server
• Can use broadcast/multicast directly
• Disadvantages
• Loose server advantages
• When to use
• Works better on a LAN or bridged LAN

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AOIM Software Layer
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AOIM Software Layer

• Area of Interest Management (AOIM) software layer
• Assigns packets to the appropriate multicast
  groups
• Keeps track of what groups are available
• Packets not part of subscribed multicast groups
  are killed off at the network interface unit
  (hardware) rather than at the applications layer
• Takes care on incoming/outgoing streaming
  information (video and audio)

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Recommendations for Our System

• DONTs
• Two-Player unless
• Only two players allowed
• Multiplayer client-server w/ multiple servers
  unless
• Have multiple groups that communicate
  infrequently
• Have high speed connections gt 10Mbps

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Recommendations for Our System

• DOs
• Multiplayer client-server
• Main DB located at server end and multicasts
  models only when needed
• Server only machine that needs multicasting
  abilities, all other machines only have to
  send/receive packets to server
• Server controls who holds the token in a token
  ring (professors computer) by switching which
  port it listens to
• Server-Player communication can use TCP/IP for
  reliable one-to-one connection UDP/IP (or other)
  for multicasting
• Server should be high performance, others can
  have lower performance (lower cost to implement)

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Recommendations for Our System

• DOs
• Peer-to Peer
• Each computer has its own copy of the DB (less
  network traffic)
• All machines need multicasting abilities
• Token passed from player to player
• Use UDP/IP (or other) for multicasting
• All machines should be high performance