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Cyclone DDS

CycloneDDS web site

install

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sudo apt install ros-humble-rmw-cyclonedds-cpp

CycloneDDS XML configuration

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export CYCLONEDDS_URI=file://$PWD/cyclonedds.xml
export RMW_IMPLEMENTATION=rmw_cyclonedds_cpp

cyclonedds version

CycloneDDS has xml configuration file for runtime configuration that changed between versions.

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dpkg -s ros-humble-cyclonedds

ros humble ver(0.10.5)

configuration

tools

tips / best practice

CycloneDDS protocols

SSPDP and SEDP are the two core discovery protocols that enable nodes to find and communicate with each other automatically.

Protocol Full Name Role
SPDP Simple Participant Discovery Protocol Discovers other DDS participants (nodes) on the network
SEDP Simple Endpoint Discovery Protocol Discovers the publishers and subscribers (topics, types, QoS) within each participant

SPDP (Simple Participant Discovery Protocol) is the first step in DDS discovery. It:

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- Broadcasts participant info (GUID, capabilities) using multicast on UDP port 7400 (domain 0).
- Helps nodes find each other without a centralized registry.
- Uses periodic announcements.
- In CycloneDDS:
    - SPDP is what shows up in tcpdump as packets to 239.255.0.1:7400 (default multicast group).

SEDP (Simple Endpoint Discovery Protocol):

Once SPDP discovers participants, SEDP kicks in to share:

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- What topics each node publishes or subscribes to
- Message types
- QoS policies

Demo: CycloneDDS between two machines

Ros humble cyclonedds version 0.10.5

machine 1

cyclonedds.xml
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<?xml version="1.0" encoding="UTF-8"?>
<CycloneDDS xmlns="https://cdds.io/config" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="https://cdds.io/config https://raw.githubusercontent.com/eclipse-cyclonedds/cyclonedds/master/etc/cyclonedds.xsd">
  <Domain Id="any">
    <General>
       <AllowMulticast>true</AllowMulticast>
       <!-- <AllowMulticast>spdp</AllowMulticast> -->
    </General>
  </Domain>
</CycloneDDS>

AllowMulticast

Both configurations are valid true and spdp .

The setting controls which parts of DDS discovery and communication are allowed to use multicast.

  • true: allow all multicast traffic,
  • spdp: only discovery uses multicast, other communication is unicast
  • false: unicast only

machine 2

cyclonedds.xml
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<?xml version="1.0" encoding="UTF-8"?>
<CycloneDDS xmlns="https://cdds.io/config" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="https://cdds.io/config https://raw.githubusercontent.com/eclipse-cyclonedds/cyclonedds/master/etc/cyclonedds.xsd">
  <Domain Id="any">
    <General>
      <!-- <AllowMulticast>true</AllowMulticast> -->
        <Interfaces>
          <NetworkInterface autodetermine="false" name="enx5c857e356893"/>
        </Interfaces>
    </General>

  </Domain>

NetworkInterface

The NetworkInterface setting is used to specify which network interface to use for communication.

  • autodetermine="false": disables automatic detection of the network interface.
  • name="enx5c857e356893": specifies the name of the network interface to use.

Test

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# machine 1
ros2 topic pub xxx std_msgs/String "data: hello world" -r 1

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# machine 2
ros2 topic echo xxx

System configuration recommendation

ros2 rmw cyclone settings

  • net.core.rmem_max
  • net.core.rmem_default
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# Add settings to sysctl 
echo "net.core.rmem_max=8388608\nnet.core.rmem_default=8388608\n" | sudo tee /etc/sysctl.d/60-cyclonedds.conf

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