1.1. What is RTI Connext DDS Micro?¶
RTI Connext DDS Micro is network middleware for distributed real-time applications. It provides the communications service programmers need to distribute time-critical data between embedded and/or enterprise devices or nodes. Connext DDS Micro uses the publish-subscribe communications model to make data distribution efficient and robust. Connext DDS Micro simplifies application development, deployment and maintenance and provides fast, predictable distribution of time-critical data over a variety of transport networks. With Connext DDS Micro, you can:
- Perform complex one-to-many and many-to-many network communications.
- Customize application operation to meet various real-time, reliability, and quality-of-service goals.
- Provide application-transparent fault tolerance and application robustness.
- Use a variety of transports.
Connext DDS Micro implements the Data-Centric Publish-Subscribe (DCPS) API within the OMG’s Data Distribution Service (DDS) for Real-Time Systems. DDS is the first standard developed for the needs of real-time systems. DCPS provides an efficient way to transfer data in a distributed system.
With Connext DDS Micro, systems designers and programmers start with a fault-tolerant and flexible communications infrastructure that will work over a wide variety of computer hardware, operating systems, languages, and networking transport protocols. Connext DDS Micro is highly configurable so programmers can adapt it to meet the application’s specific communication requirements.
1.1.1. RTI Connext DDS Cert versus RTI Connext DDS Micro¶
RTI Connext DDS Micro and RTI Connext DDS Cert originate from the same source base, but as of Connext DDS Micro 2.4.6 the two are maintained as two independent releases. The latest release with certification evidence is Connext DDS Cert 2.4.5. However, features that exist in Connext DDS Micro and Connext DDS Cert behave identically and the source code is written following identical guidelines. Connext DDS Cert only supports a subset of the features found in Connext DDS Micro. In the API reference manuals, APIs that are supported by Connext DDS Cert are clearly marked.
1.1.2. Optional Certification Package¶
An optional Certification Package is available for systems that require certification to DO-178C or other safety standards. This package includes the artifacts required by a certification authority. The Certification Package is licensed separately from Connext DDS Cert.
To use an existing Certification Package, an application must be linked against the same libraries included in the Certification Package. Contact RTI Support, firstname.lastname@example.org, for details.
1.1.3. Publish-Subscribe Middleware¶
Connext DDS Micro is based on a publish-subscribe communications model. Publish-subscribe (PS) middleware provides a simple and intuitive way to distribute data. It decouples the software that creates and sends data—the data publishers—from the software that receives and uses the data—the data subscribers. Publishers simply declare their intent to send and then publish the data. Subscribers declare their intent to receive, then the data is automatically delivered by the middleware. Despite the simplicity of the model, PS middleware can handle complex patterns of information flow. The use of PS middleware results in simpler, more modular distributed applications. Perhaps most importantly, PS middleware can automatically handle all network chores, including connections, failures, and network changes, eliminating the need for user applications to program of all those special cases. What experienced network middleware developers know is that handling special cases accounts for over 80% of the effort and code.
1.2. Supported DDS Features¶
Connext DDS Micro supports a subset of the DDS DCPS standard. A brief overview of the supported features are listed here. For a detailed list, please refer to the C API Reference and C++ API Reference.
1.2.1. DDS Entity Support¶
Connext DDS Micro supports the following DDS entities. Please refer to the documentation for details.
1.2.2. DDS QoS Policy Support¶
Connext DDS Micro supports the following DDS Qos Policies. Please refer to the documentation for details.
1.3. Standards and Interoperability¶
Connext DDS Micro implements the Object Management Group (OMG) Data Distribution Service (DDS) standard (version 1.4), and the Real-Time Publish-Subscribe (RTPS) wire interoperabilty protocol standard (version 2.2).
Connext DDS Micro supports a subset of the submessages defined by the Real-Time Publish-Subscribe (RTPS) interoperability specification. Data fragment submessages are not supported. The messages are compatible with Wireshark and its RTPS packet dissector.
Connext DDS Micro and Connext DDS are wire-interoperable, unless stated otherwise (see below), and API compatible for APIs specified by the DDS standard. For non-standard APIs, Connext DDS Micro and Connext DDS are incompatible. Please refer to Working with RTI Connext DDS Micro and RTI Connext DDS for more information.
1.3.1. DDS Wire Compatability¶
Connext DDS Micro is compliant with RTPS 2.2, but does not support and ignore the following RTPS sub-messages:
|Submessage||Supported||DDS Standard||Connext DDS Core|
1.3.2. Profile / Feature¶
Connext DDS Micro does not support mutable Qos policies.
|Submessage||Supported||DDS Standard||Connext DDS Core|
- VOLATILE and TRANSIENT_LOCAL
- No, DW offers access_scope = TOPIC, coherent_access = FALSE and ordered_access = TRUE DR requests access_scope = INSTANCE, coherent_access = FALSE and ordered_access = FALSE
- AUTOMATIC (infinite only), MANUAL_BY_PARTICIPANT (infinite only), MANUAL_BY_TOPIC (finite and infinite)
- BEST_EFFORT and RELIABLE, only max_blocking_time=0
- DataWriter: Yes, DataReader only supports BY_RECEPTION_TIMESTAMP
- Only KEEP_LAST
- Only finite resource-limits
- The following are supported: - heartbeat_period - heartbeats_per_max_samples - max_heartbeat_retries - max_send_window_size - rtps_object_id
- DomainParticipant only
1.3.3. DDS API Support¶
For supported APIs, please refer to:
1.4. RTI Connext DDS Documentation¶
Throughout this document, we may suggest reading sections in other RTI Connext DDS documents. These documents are in your RTI Connext DDS installation directory under rti-connext-dds-<version>/doc/manuals. A quick way to find them is from RTI Launcher’s Help panel, select “Browse Connext Documentation”.
Since installation directories vary per user, links are not provided to these documents on your local machine. However, we do provide links to documents on the RTI Documentation site for users with Internet access.
New users can start by reading Parts 1 (Introduction) and 2 (Core Concepts) in the RTI Connext DDS Core Libraries User’s Manual. These sections teach basic DDS concepts applicable to all RTI middleware, including RTI Connext DDS Professional and RTI Connext DDS Micro. You can open the RTI Connext DDS Core Libraries User’s Manual from RTI Launcher’s Help panel.
The RTI Community provides many resources for users of DDS and the RTI Connext family of products.
1.5. OMG DDS Specification¶
For the original DDS reference, the OMG DDS specification can be found in the OMG Specifications under “Data Distribution Service”.
1.6. Other Products¶
RTI Connext DDS Micro is one of several products in the RTI Connext family of products:
RTI Connext DDS Cert is a subset of RTI Connext DDS Micro. Connext DDS Cert does not include the following features because Certification Evidence is not yet available for them. If you require Certification Evidence for any of these features, please contact RTI.
- C++ language API.
- Multi-platform support.
- Dynamic endpoint discovery.
- delete() APIs (e.g. delete_datareader())
RTI Connext DDS Professional addresses the sophisticated databus requirements in complex systems including an API compliant with the Object Management Group (OMG) Data Distribution Service (DDS) specification. DDS is the leading data-centric publish/subscribe (DCPS) messaging standard for integrating distributed real-time applications. Connext DDS Professional is the dominant industry implementation with benefits including:
- OMG-compliant DDS API
- Advanced features to address complex systems
- Advanced Quality of Service (QoS) support
- Comprehensive platform and network transport support
- Seamless interoperability with rtime
RTI Connext DDS Professional includes rich integration capabilities:
- Data transformation
- Integration support for standards including JMS, SQL databases, file, socket, Excel, OPC, STANAG, LabVIEW, Web Services and more
- Ability for users to create custom integration adapters
- Optional integration with Oracle, MySQL and other relational databases
- Tools for visualizing, debugging and managing all systems in real-time
RTI Connext DDS Professional also includes a rich set of tools to accelerate debugging and testing while easing management of deployed systems. These components include:
- Administration Console
- Distributed Logger
- Monitoring Library
- Recording Service