Connect any IIoT Device: a Guide to DDS
Connect any IIoT Device: a Guide to DDS
Want to learn more about DDS and how it works? Check out this post to learn more about DDS and why it is useful for securing small embedded sensors on your machines.
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Nick Pridham, from Hamersham, explains how DDS technology works.
What Is DDS?
DDS provides a way for devices to exchange data on local or remote networks. It is a small footprint network stack that consumes minimal resources and can be deployed on any device. Small embedded sensors running on machines in the field or cloud servers running in data centers can all run DDS. DDS will take care of data exchange between any of these devices.
How Does DDS Work?
DDS works on the publish/subscribe principle. This means data exchange is peer-to-peer and does not need a message broker or a central server. A device with data to offer to a network (publisher) is matched with a device that has a requirement to receive this data (subscriber). Matching is done via Data TOPICS and a discovery process. A Data TOPIC could be a package of machine health information, such as temperatures, speeds, working hours, and fault codes. This Data TOPIC could be required by a neighboring device of the same type, a data logger, a cloud server, a PLC controller, and/or a measuring diagnostic tool.
In other words, any DDS device can exchange data with any other DDS device. Data can be exchanged between publishers and subscribers via unicast, multicast, or a broadcast, meaning data from one device can easily reach thousands of other devices.
Why Would I Use DDS?
DDS saves engineering time and money by automating data exchange between devices. As networks grow to thousands of devices, network configuration and management can be cumbersome.
If each new device added to a network needs configuring with IP addresses and port numbers then this can consume large amounts of engineering time.
DDS takes care of this in the background and makes sure network participants can exchange data on the basis of TOPICs.
DDS, therefore, allows networks to scale automatically. Thousands of devices can join a network auto-configure and then publish or subscribe to data TOPICs. Very often, IIOT network scenarios are dynamic, meaning thousands of devices can leave a network too. DDS ensures that large numbers of devices can join or leave a network automatically.
How Is Data Transfer Flexibility Achieved?
DDS provides 25 different quality of service (QOS) configurations. This means data subscribers can choose communication profiles appropriate to their requirements. Examples of DDS QOS configurations are:
- History: Specify how much data history is available to new network participants;
- Reliability: Specify whether data receipt can be tolerant of dropped packets;
- Deadline: A network mechanism that will error-handle late delivery of messages;
- Filtration: A subscriber may not want to receive every data sample for a particular topic;
- Ownership Strength: A subscriber can choose which duplicate data to use based on publisher strength.
Who Uses DDS?
DDS is used in a very wide range of industrial sectors where advanced connectivity is required. The following use case descriptions are some of many:
Defence: DDS is widely used in defense vehicles for providing a communication backbone for all vehicle subsystems, including weapons, driveline, ramps, navigation, and data logging. In this type of application, bridges are made from CANBUS to DDS in order to create a common data space.
DAQ and Instrumentation: DAQ networking has always traditionally been constructed on a point-to-point architecture. DDS gives DAQ applications a completely data-centric approach. DAQ modules can communicate with each other, individual sensors, and remote servers for bulk data logging and display/diagnostic devices.
Energy: The trend to switch to renewable energy means that large numbers of individual power generation devices have to be controlled. Wind turbines, solar farms, and hydro installations all now have to be able to be switched on an off according to demand. Highly distributed network architectures are used with DDS being the command, control, and feedback protocol. DDS provides control signals that open/close contactors and then feedback to command software that monitors how much power each device is producing.
Is DDS a New Concept?
Despite its sophisticated capabilities, DDS has in fact been in existence since 2001. It was started as a solution to problems with stove pipe communications in US Navy applications. DDS was designed to provide a data-centric communications environment for seaborne applications to enable many different subsystems to communicate.
As an established technology, DDS is an open standard with multiple vendors and a governing standards body, the Object Management Group (OMG). As there are multiple vendors of DDS, there is no commercial lock-in with any implementation. Vendor meetings under the governance of OMG meet four times per year to discuss improvements and changes.
To find out more about DDS, visit: https://hamersham.com/dds-network-middleware/
Published at DZone with permission of Kate Wobschall . See the original article here.
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