Compatibility
=============

Below is basic compatibility information for this release.

.. For a complete list of supported OMG standards used by
   |CONNEXTDDS_ITALIC| in this release, see <URL>.

.. note::

   For backward-compatibility information between this and previous releases, 
   see the *Migration Guide* on the RTI Community Portal (https://community.rti.com/documentation).

Wire Protocol Compatibility
---------------------------

|CONNEXTDDS_ITALIC| communicates over the wire using the formal
Real-Time Publish-Subscribe (RTPS) protocol. RTPS has been developed
from the ground up with performance, interoperability and extensibility
in mind. The RTPS protocol is an international standard managed by the
OMG. The RTPS protocol has built-in extensibility mechanisms that enable
new revisions to introduce new message types, extend the existing
messages, or extend the Quality of Service settings in the
product—without breaking interoperability.

RTPS 1.0 was introduced in 2001. The currently supported version is 
|OMG_RTPS_SPEC|, although some features are not supported. Unsupported 
features currently are FilteredCountFlag in GAP Submessage, HeartbeatFrag 
Submessage, and ALIVE_FILTERED instance state. RTI plans to 
maintain interoperability between middleware versions based on RTPS 2.1. 
For more details, see :numref:`rtps-versions` :ref:`rtps-versions`.

:numref:`rtps-versions` :ref:`rtps-versions` shows RTPS versions supported for each
|CONNEXTDDS_ITALIC| release. In general, RTPS 2.1 and higher versions
are interoperable, unless noted otherwise. RTPS 2.0 and RTPS 1.2 are
incompatible with current (4.2e and later) versions of
|CONNEXTDDS_ITALIC|.

Although RTPS 2.1 and higher versions are generally interoperable, there
may be specific wire protocol interoperability issues between
|CONNEXTDDS_ITALIC| releases. These issues are documented in the "Wire
Protocol" section for your release, in the |MIGRATIONGUIDECOMMPORTAL|.
Wire protocol issues between 5.3.1 and previous releases are documented
in the |CORERELEASENOTES| for release 5.3.1.

.. _rtps-versions:

.. list-table:: RTPS Versions
    :name: TableRTPSVersionsReleaseNotes
    :widths: 80 20 20
    :header-rows: 1

    * - Connext Release
      - RTPS Standard Version [#f1]_
      - RTPS Protocol Version [#f2]_
    * - |CONNEXTDDS_ITALIC| 7.1.0 and above
      - 2.5 (partial support)
      - 2.5
    * - |CONNEXTDDS_ITALIC| 6 and 7.0.0
      - 2.3 (partial support)
      - 2.3
    * - |CONNEXTDDS_ITALIC| 5.2 and 5.3
      - 2.2
      - 2.1
    * - |CONNEXTDDS_ITALIC| 4.5f - 5.1
      - 2.1
      - 2.1
    * - Data Distribution Service 4.2e - 4.5e
      - 2.1
      - 2.1
    * - Data Distribution Service 4.2c
      - 2.0
      - 2.0
    * - Data Distribution Service 4.2b and lower
      - 1.2
      - 1.2

.. rubric:: Footnotes

.. [#f1] Version number of the RTPS standards document, |OMG_RTPS_SPEC|
.. [#f2] RTPS wire protocol version number that |CONNEXTDDS_ITALIC| announces in messages it puts on the wire


Code and Configuration Compatibility
------------------------------------

The |CONNEXTDDS_ITALIC| core uses an API that is an extension of the
|OMG_DDS_SPEC|. RTI strives to maintain API compatibility between
versions, but will conform to changes in the OMG DDS standard.

The |CONNEXTDDS_ITALIC| core primarily consists of a library and a set
of header files. In most cases, upgrading simply requires you to
recompile your source using the new header files and link the new
libraries. In some cases, minor modifications to your application code
might be required; any such changes are noted in the
|MIGRATIONGUIDECOMMPORTAL|. The |MIGRATIONGUIDETITLEONLY| also
indicates whether and how to regenerate code.

Extensible Types Compatibility
------------------------------

This release of |CONNEXTDDS_ITALIC| includes partial support for the
|OMG_XTYPES_SPEC| (DDS-XTypes) from the Object Management Group (OMG).
This support allows systems to define data types in a more flexible way,
and to evolve data types over time without giving up portability,
interoperability, or the expressiveness of the DDS type system.

For information related to compatibility issues associated with the
Extensible Types support, see the |MIGRATIONGUIDECOMMPORTAL|. See also
the *RTI* |CONNEXTDDS_ITALIC| *Core Libraries Extensible Types Guide*
for a full list of the supported and unsupported extensible types
features\ *.*