RTI Connext Interoperability

HDDS is certified compatible with RTI Connext DDS 6.x and 7.x.

Tested Configurations

• RTI Connext 6.1.0: 50/50 samples (RTPS 2.3)
• RTI Connext 7.3.0: 49/50 samples (RTPS 2.5)

Version Differences

Aspect	RTI 6.x	RTI 7.x
RTPS Version	2.3	2.5
Wire Format	Standard	Enhanced
Vendor PIDs	Standard	Additional

HDDS handles both versions automatically without code changes.

Requirements

• RTI Connext DDS 6.0+ or 7.x (Professional or Micro)
• Same domain ID on both ends
• Compatible QoS policies

Quick Test

HDDS Publisher

use hdds::{Participant, QoS, TransportMode};

// Types are generated from IDL using hddsgen:
//   hddsgen gen rust SensorData.idl
mod generated { include!("generated/sensor_data.rs"); }
use generated::sensors::SensorData;

fn main() -> Result<(), hdds::Error> {
    let participant = Participant::builder("hdds_publisher")
        .domain_id(0)
        .with_transport(TransportMode::UdpMulticast)
        .build()?;

    let topic = participant.topic::<SensorData>("SensorTopic")?;
    let writer = topic.writer().qos(QoS::reliable()).build()?;

    for i in 0.. {
        writer.write(&SensorData {
            sensor_id: 1,
            value: i as f32 * 0.1,
        })?;
        std::thread::sleep(std::time::Duration::from_millis(100));
    }
    Ok(())
}

RTI Connext Subscriber (C++)

#include <dds/dds.hpp>

int main() {
    dds::domain::DomainParticipant participant(0);
    dds::topic::Topic<SensorData> topic(participant, "SensorTopic");
    dds::sub::Subscriber subscriber(participant);
    dds::sub::DataReader<SensorData> reader(subscriber, topic);

    while (true) {
        auto samples = reader.take();
        for (const auto& sample : samples) {
            if (sample.info().valid()) {
                std::cout << "Sensor " << sample.data().sensor_id()
                          << ": " << sample.data().value() << std::endl;
            }
        }
        std::this_thread::sleep_for(std::chrono::milliseconds(100));
    }
}

IDL Type Definition

RTI Connext uses its own code generator:

// SensorData.idl
struct SensorData {
    @key long sensor_id;
    float value;
};

Generate for RTI Connext:

rtiddsgen -language C++11 SensorData.idl

Generate for HDDS:

hddsgen gen rust SensorData.idl

Encapsulation Format

RTI Connext typically uses PL_CDR_BE (big-endian):

Phase	RTI Format	HDDS Support
SPDP	PL_CDR_BE (0x0002)	✅
SEDP	PL_CDR_BE (0x0002)	✅
User Data	CDR_BE / PL_CDR_BE	✅

HDDS automatically handles big-endian format from RTI.

QoS Configuration

RTI Connext (XML)

<?xml version="1.0"?>
<dds>
    <qos_library name="HddsInterop">
        <qos_profile name="Default">
            <datawriter_qos>
                <reliability>
                    <kind>RELIABLE_RELIABILITY_QOS</kind>
                    <max_blocking_time>
                        <sec>1</sec>
                        <nanosec>0</nanosec>
                    </max_blocking_time>
                </reliability>
                <durability>
                    <kind>TRANSIENT_LOCAL_DURABILITY_QOS</kind>
                </durability>
                <history>
                    <kind>KEEP_LAST_HISTORY_QOS</kind>
                    <depth>100</depth>
                </history>
            </datawriter_qos>
        </qos_profile>
    </qos_library>
</dds>

HDDS (Rust)

use hdds::QoS;

let qos = QoS::reliable().keep_last(100).transient_local();

Network Configuration

Multicast (Default)

Standard RTPS multicast works out of the box:

Discovery: 239.255.0.1:7400 (domain 0)

Unicast/WAN Configuration

HDDS:

export HDDS_SPDP_UNICAST_PEERS="192.168.1.50:7400,192.168.1.51:7400"

RTI Connext (XML):

<participant_qos>
    <discovery>
        <initial_peers>
            <element>192.168.1.50</element>
            <element>192.168.1.51</element>
        </initial_peers>
    </discovery>
</participant_qos>

Known Differences

SPDP Fragmentation

RTI Connext may fragment SPDP announcements across multiple DATA_FRAG submessages. HDDS handles this automatically.

TypeObject Compression

RTI uses ZLIB compression for TypeObject data. HDDS supports decompression.

Parameter Ordering

RTI expects specific parameter ordering in SEDP. HDDS follows RTI's expected order for maximum compatibility.

RTI Admin Console

To monitor HDDS participants in RTI Admin Console:

1. Open Admin Console
2. Connect to domain (matching domain ID)
3. HDDS participants appear under "Participants"
4. Topics, endpoints visible in tree view

Troubleshooting

RTI Doesn't See HDDS

1. Check domain ID matches
2. Enable HDDS diagnostics:

   export HDDS_INTEROP_DIAGNOSTICS=1
   export RUST_LOG=hdds=debug

3. Check RTI Distributed Logger for errors

HDDS Doesn't See RTI

1. Verify RTI is publishing on expected multicast
2. Check firewall allows UDP on ports 7400-7500
3. Try unicast peers instead of multicast

Data Not Received

1. Verify QoS compatibility (reliability, durability)
2. Check type names match exactly (case-sensitive)
3. Verify key fields match (@key annotation)

Timestamp Issues

RTI uses source timestamps heavily. Ensure system clocks are synchronized if using BY_SOURCE_TIMESTAMP ordering.

Performance Benchmarks

Testing on same machine, domain 0:

Metric	RTI → HDDS	HDDS → RTI
Discovery	~1.5s	~1.5s
Latency (1KB)	0.8 ms	1.2 ms
Throughput	50K msg/s	45K msg/s

Next Steps

• QoS Mapping - Detailed QoS translation
• Example - Complete working example