13. Typical Use-Cases

Fast DDS is highly configurable, which allows for its use in a large number of scenarios. This section provides configuration examples for the following typical use cases when dealing with distributed systems:

• Fast DDS over WIFI. Presents a case where Discovery through multicast communication is a challenge. This example shows how to:

  • Configure an initial list of peers with the address-port pairs of the remote participants (see Configuring Initial Peers).

  • Disable the multicast discovery mechanism (see Disabling multicast discovery).

  • Configure a SERVER discovery mechanism (see Discovery Server).

• Well Known Network Deployments. Describes a situation where the entire entity network topology (Participants, Publishers, Subscribers, and their addresses and ports) are known beforehand. In these kind of environments, Fast DDS allows to completely avoid the discovery phase configuring a STATIC discovery mechanism.

• Topics with many subscribers. In cases where there are many DataReaders subscribed to the same Topic, using multicast delivery can help reducing the overhead in the network and CPU.

• Large Data Rates. Presents configuration options that can improve the performance in scenarios where the amount of data exchanged between a Publisher and a Subscriber is large, either because of the data size or because the message rate. The examples describe how to:

  • Configure the socket buffer size (see increase the buffers size).

  • Limit the publication rate (see Flow Controllers).

  • Tune the size of the socket buffers (see Increasing socket buffers size).

  • Tune the Heartbeat period (see Tuning Heartbeat Period).

  • Configure a non-strict reliable mode (see Using Non-strict Reliability).

• Real-time behavior. Describes the configuration options that allows using Fast DDS on a real-time scenario. The examples describe how to:

  • Configure memory management to avoid dynamic memory allocation (see Tuning allocations).

  • Limit the blocking time of API functions to have a predictable response time (see Non-blocking calls).

• Reduce memory usage. For use cases with memory consumption constraints, Fast DDS can be configured to reduce memory footprint to a minimum by adjusting different QoS policies.

• ROS 2 using Fast DDS middleware. Since Fast DDS is the default middleware implementation in the OSRF Robot Operation System 2 (ROS 2), this documentation includes a whole independent section to show the use of the library in ROS 2, and how to take full advantage of Fast DDS wide set of capabilities in a ROS 2 project.

• 13.1. Fast DDS over WIFI
  • 13.1.1. Configuring Initial Peers
  • 13.1.2. Disabling multicast discovery
  • 13.1.3. Discovery Server
• 13.2. Well Known Network Deployments
  • 13.2.1. Peer-to-Peer Participant Discovery Phase
  • 13.2.2. STATIC Endpoint Discovery Phase
• 13.3. Large Data Rates
  • 13.3.1. Increasing socket buffers size
  • 13.3.2. Flow Controllers
  • 13.3.3. Tuning Heartbeat Period
  • 13.3.4. Using Non-strict Reliability
  • 13.3.5. Practical Examples
• 13.4. Topics with many subscribers
• 13.5. Real-time behavior
  • 13.5.1. Tuning allocations
  • 13.5.2. Non-blocking calls
• 13.6. Reduce memory usage
  • 13.6.1. Limiting Resources
  • 13.6.2. Set Dynamic Allocation