ROS 2 Middleware: How the RMW Layer Decouples Robot Apps from DDS Backends

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This chapter from the STATERA Library's Robotics Communication volume examines the Robot Middleware (RMW) layer in ROS 2. It explains that the RMW was introduced to overcome the tight coupling between application code and communication libraries found in earlier robotics frameworks. The article describes ROS 2's layered stack, in which applications sit atop client libraries such as rclcpp and rclpy, followed by the RCL and then the RMW. The RMW translates ROS concepts into DDS concepts, allowing applications to remain portable across different DDS vendors such as Fast DDS, Cyclone DDS, and Connext DDS.

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