Torque Network Library

1
Torque Network Library

• Presented by Ryan Wentzel

2
Overview

• What is TNL?
• Background
• Limitations of Computer Networks
• How Does TNL Address These Issues?
• Resources

3
What is TNL?

• The Torque Network Library is a robust, secure,
  easy to use, cross-platform C networking API
  designed for high performance simulations and
  games.

4
Background

• Networking technology used in Tribes and Tribes
  2.
• GarageGames released TNL as a stand-alone product
  in 2004 under GPL, independent developer, and
  commercial licenses.

5
Limitations of Computer Networks

• Limited bandwidth There is a limit to the rate
  at which hosts on a network can send data to each
  other.
• Packet loss - Data transmitted over a network can
  be lost or corrupted.
• Latency (network lag) - It takes time for data
  sent by one host to another to arrive

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How Does TNL Address These Issues?

• Limited bandwidth
• Send static data once, or not at all
• Compress data to the minimum space necessary
• BitStream class is used to write standard data
  types into a compressed packet.
• Only send information that is relevant to the
  client
• For example, objects outside of a clients
  visible distance arent relevant
• TNL allows the programmer to specify which
  objects are relevant for each client

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How Does TNL Address These Issues?

• Limited bandwidth
• Prioritize object updates
• TNL allows the programmer to create policies for
  determining which objects are more or less
  important to a client
• Objects with more importance are updated more
  frequently
• Only update the parts of an object that have
  changed
• If a client fires a weapon only the change in
  ammunition needs to be updated not the clients
  entire state

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How Does TNL Address These Issues?

• Packet Loss TNL implements various delivery
  policies
• Guaranteed Ordered Data Data that would
  typically be sent using TCP
• TNL uses Event objects and RPC method calls to
  send Guaranteed Ordered data.
• Guaranteed Data Similar to Guaranteed Ordered
  data
• A client can process data immediately upon
  arrival rather than waiting for ordered data that
  may have been dropped.

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How Does TNL Address These Issues?

• Packet loss - TNL implements various delivery
  policies
• Unguaranteed Data Data that would typically be
  sent using UDP.
• If the packet is dropped the data is not resent
• Quickest Delivery Data For data that must
  arrive quickly.
• The data is sent with each outgoing packet until
  the receiving host acknowledges receipt of it
• Could be used for sending client movement data

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How Does TNL Address These Issues?

• Latency
• Interpolation - used to smoothly move an object
  from where the client thinks it is to where the
  server declares it to be over some short period
  of time
• Extrapolation Make a guess about an objects
  current state based on a known past state
• Client-side prediction similar to extrapolation
  but uses input data from client
• You dont need to wait for the server to tell you
  where you moved to

11
Resources

• OpenTNL website - http//www.opentnl.org/
• TNL Architectural Overview - http//opentnl.source
  forge.net/doxydocs/archoverview.html
• Hello World example - http//opentnl.sourceforge
  .net/doxydocs/simpletutorial.html