REVIEW 3 major objections 5 minor 1 cited by
Performance Evaluation of ROS2-DDS middleware implementations facilitating Cooperative Driving in Autonomous Vehicle
T0 review · 3 major / 5 minor · reviewed 2026-08-11 · deepseek-v4-flash
Pith's one-line read This paper claims that current ROS2 DDS vendor implementations, used for different-domain communication over wireless links, cannot meet hard real-time cooperative driving requirements, and no vendor wins in all cases.
desk verdict A useful but statistically thin benchmark of cross-domain ROS2/DDS bridging; the latency metric in Eq. (3) is not validated, so the hard-real-time conclusion is overstated. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The argument is carried by a ping-pong round-trip test with a relay node. A publisher in one DDS domain (e.g., domain 5) timestamps a message and sends it; a subscriber in another domain (e.g., domain 10) receives it and relays it back on a second topic; the publisher timestamps the return. One-way latency is computed as (RTT - intermediate-process time)/2, where the intermediate time is measured locally on the relay node as the gap between receiving and relaying. Every cross-domain path therefore contains a vendor-specific bridging service (Zenoh plugin, Integration Service, or Routing Service), and the latency behavior the paper reports is the behavior of those bridges plus the transport. The DDS domain is the scoping mechanism that forces the relay; the bridge is the object whose performance is under test.
What would settle it
Re-run the cross-domain ping-pong experiment on a wireless link with synchronized clocks on both nodes and measure one-way latency directly in each direction; if the directly measured values diverge from the paper's (RTT - intermediate-process time)/2 estimate, the absolute latency conclusions are biased. A second check is to repeat the 502KB file-size sweep with finer size steps to confirm whether the spike is a real fragmentation threshold.
Extended reading notes
Core claim
The central discovery is an empirical characterization of cross-domain latency in ROS2. Because DDS limits participant counts per domain, a vehicle or platoon with many nodes must bridge across domains via vendor-specific services: Zenoh for Eclipse Cyclone DDS, Integration Service for eProsima Fast-DDS, and Routing Service for RTI Connext DDS. Across a large parameter sweep, same-domain communication generally beat different-domain communication; eProsima Fast-DDS was worst at cross-domain communication for all data types, connectivities, and devices; Cyclone DDS was best for large files over wireless different domains; and RTI Connext showed the smallest gap between same-domain and different-domain performance. The paper also observed a systematic latency spike for 502KB binary files across vendors. The conclusion is that different-domain DDS over wireless is not hard-real-time capable at this moment, and the likely culprit is the bridging services.
Load-bearing premise
The load-bearing premise is that one-way latency equals half of the round-trip time minus half of the relay node's measured handling time; if the outward and return wireless paths take different amounts of time, which is common on wireless links, the reported latencies are systematically biased.
Editorial extensions
If this is right
- Developers should keep ROS2 nodes in the same DDS domain whenever possible, since same-domain communication usually had lower latency.
- eProsima Fast-DDS should be avoided for different-domain communication; it showed the worst performance in every tested wired and wireless scenario.
- RTI Connext DDS is the safer default when an application needs both same-domain and cross-domain links, because it showed the smallest latency gap between the two.
- For large binary files sent across wirelessly connected different domains, Eclipse Cyclone DDS provided better latency than the alternatives.
- Binary frames around 502KB should be investigated or avoided: they triggered a latency spike across DDS implementations, sometimes exceeding the latency of 1MB frames.
Reading between the lines
- The paper's latency formula assumes symmetric one-way paths; on wireless links this is often false, so the absolute latency values may be biased even if the relative vendor rankings hold.
- If hard real-time cannot be met across DDS domains, the practical route for cooperative driving may be to keep safety-critical control loops inside one domain or on a dedicated link, and use cross-domain DDS only for non-critical perception data.
- The 502KB spike hints at a fragmentation or buffer threshold near that size; probing with sizes between 400KB and 600KB could turn the anomaly into a diagnosable implementation detail.
- The evaluation is static in the sense of fixed QoS; combining the same setup with deadline-based QoS or 5G transport could test whether cross-domain DDS at least meets soft real-time constraints.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper evaluates three vendor-specific DDS implementations (Eclipse Cyclone DDS, eProsima Fast DDS, RTI Connext DDS) with their bridging services in ROS2 Humble for same-domain and different-domain communication over wired and wireless links. It reports latency measurements for binary, string, and IMU data types on Raspberry Pi 3/4, Jetson Nano, and laptops, and concludes that no single DDS vendor dominates, that eProsima performs worst for different-domain communication, and that ROS2 vendor-specific DDS implementations are not capable of fulfilling hard real-time requirements for cooperative driving over wireless.
Significance. If validated, the comparison of same-domain versus different-domain bridging across vendors would be a useful practical reference for ROS2 developers in cooperative driving and multi-robot systems. The paper has concrete strengths: it uses heterogeneous physical hardware, multiple data types, a real camera stream test, and it makes the experiment code available online. However, the central latency metric in Eq. (3) rests on untested symmetry assumptions, and the reported comparisons lack any statistical confidence information, so the quantitative vendor ranking and the hard-real-time conclusion are not yet established.
major comments (3)
- [§3.2, Eq. (3)] The latency estimator in Eq. (3) is not a valid one-way latency. The RTT includes the initiating publisher's send-side and receive-side processing, which are not captured by the relay's T4−T3 interval, and the halving assumes the two legs are symmetric in both network conditions and endpoint processing. Since the publisher and subscriber are different devices (Table 2), their per-message processing times are not equal; on Wi-Fi the forward and return paths can also differ due to contention, retries, and rate adaptation. All §4 comparisons and the §6 hard-real-time conclusion are built on this quantity. The paper should either measure one-way latency with synchronized clocks (e.g., PTP/chrony), or report RTT and intermediate-processing time separately without dividing by two, or provide a quantitative bound showing that the bias is negligible for the conclusions drawn.
- [§4] No trial counts, error bars, standard deviations, or raw latency distributions are reported. The text relies on visual descriptions of plots, including the unexpected result that 502 KB files often yield higher latency than 1 MB files (figures 3b and 3c), and the cross-vendor rankings. Without measures of dispersion or at least a stated number of repetitions per configuration, these differences cannot be distinguished from measurement noise. This undermines the central vendor-level claims, including the recommendations to avoid eProsima for different-domain communication and to prefer RTI Connext for mixed-domain workloads. Please report the number of repetitions, per-configuration statistics, and, where possible, confidence intervals.
- [§6] The claim that 'ROS2's vendor-specific DDS implementations are not capable enough to fulfill the hard real-time requirements' is not tied to any quantified deadline. Hard real-time is an application-specific property; the paper should state the assumed end-to-end latency bound (e.g., a braking or cooperative-perception deadline) and compare the measured values against that bound. Without a stated threshold, the central conclusion is not falsifiable and cannot be assessed. This is load-bearing because it motivates the entire framing of the paper as a cooperative-driving evaluation.
minor comments (5)
- [Contribution paragraph] The text says 'This paper presents a noble performance comparison' but should read 'novel performance comparison'.
- [§3.2] The word 'intermediate-processtime' appears without a space; it should be 'intermediate-process time' for consistency with the surrounding text.
- [§3.3 Software] The statement that Docker on the host network produces 'negligible latency overhead' is supported only by a citation to a general container/VM comparison; the manuscript should verify this for the specific DDS/UDP multicast workloads used, since even a small constant bias can affect absolute latency comparisons with real-time thresholds.
- [§4 figure captions] The figure captions in §4 do not fully specify axes, units, or the meaning of the plotted curves; please ensure every panel has labeled axes with latency units and a legend, and that the captions explicitly state which domain and connectivity scenario each panel represents.
- [References] Reference [24] is a shortened URL that may become unstable; use a stable identifier or direct URL, and check formatting consistency across the reference list.
Circularity Check
No circularity found: the paper's claims rest on direct experimental measurements, and the only self-referential element is a link to the authors' own code for reproducibility.
full rationale
The paper is an experimental performance evaluation, not a derivation from first principles. The central claim—that vendor-specific ROS2-DDS implementations over wireless different-domain communication cannot currently meet hard real-time requirements—is supported by direct latency measurements across physical devices, data types, frequencies, and connectivity modes. Equation (3) defines one-way latency as (RTT minus measured relay-processing time) divided by two. This is a measurement definition rather than a prediction derived from fitted parameters, and it is not circular: the quantity is computed from raw timestamps, and the conclusion is an empirical observation about the resulting values. The only self-referential item is the GitHub link in Appendix A, which provides the experimental source code; it is not used to justify any load-bearing assumption, uniqueness claim, or fitted result. The paper does not invoke any prior same-author theorem, does not smuggle in an ansatz via citation, and does not rename a known result. Any concern that Equation (3) assumes path symmetry or omits publisher-side overhead would be a correctness or validity critique of the measurement methodology, not a circularity critique. Under the stated rules, such methodological concerns do not constitute circularity, so the appropriate score is 0.
Assumptions & free parameters
assumptions (5)
- domain assumption One-way latency equals half the network round-trip time (latency = (RTT - intermediate)/2).
- domain assumption Docker containers add negligible latency overhead.
- domain assumption The relay node's intermediate processing time (T4-T3) can be subtracted linearly from round-trip time to isolate network latency.
- domain assumption ROS2 behaves similarly for the various DDS implementations apart from the middleware itself.
- domain assumption rclpy (Python client library) is a representative way to measure ROS2 communication latency.
Cite this review
Pith. "Pith review of Performance Evaluation of ROS2-DDS middleware implementations facilitating Cooperative Driving in Autonomous Vehicle." pith.science (2026). https://pith.science/paper/GTCVKWOM
@misc{pith2026241207485,
author = {Pith},
title = {Pith review of: Performance Evaluation of ROS2-DDS middleware implementations facilitating Cooperative Driving in Autonomous Vehicle},
year = {2026},
howpublished = {\url{https://pith.science/paper/GTCVKWOM}},
note = {Machine review of arXiv:2412.07485}
}
read the original abstract
In the autonomous vehicle and self-driving paradigm, cooperative perception or exchanging sensor information among vehicles over wireless communication has added a new dimension. Generally, an autonomous vehicle is a special type of robot that requires real-time, highly reliable sensor inputs due to functional safety. Autonomous vehicles are equipped with a considerable number of sensors to provide different required sensor data to make the driving decision and share with other surrounding vehicles. The inclusion of Data Distribution Service(DDS) as a communication middleware in ROS2 has proved its potential capability to be a reliable real-time distributed system. DDS comes with a scoping mechanism known as domain. Whenever a ROS2 process is initiated, it creates a DDS participant. It is important to note that there is a limit to the number of participants allowed in a single domain. The efficient handling of numerous in-vehicle sensors and their messages demands the use of multiple ROS2 nodes in a single vehicle. Additionally, in the cooperative perception paradigm, a significant number of ROS2 nodes can be required when a vehicle functions as a single ROS2 node. These ROS2 nodes cannot be part of a single domain due to DDS participant limitation; thus, different domain communication is unavoidable. Moreover, there are different vendor-specific implementations of DDS, and each vendor has their configurations, which is an inevitable communication catalyst between the ROS2 nodes. The communication between vehicles or robots or ROS2 nodes depends directly on the vendor-specific configuration, data type, data size, and the DDS implementation used as middleware; in our study, we evaluate and investigate the limitations, capabilities, and prospects of the different domain communication for various vendor-specific DDS implementations for diverse sensor data type.
Figures
Figures from the paper (3 more)
Forward citations
Cited by 1 Pith paper
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Probabilistic Latency Analysis of the Data Distribution Service in ROS 2
The paper claims a discrete-state probabilistic model for ROS 2 DDS retransmission latency, but the supplied body is the wrong manuscript, leaving the claim unverifiable.
Reference graph
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Reviewed August 11, 2026 · model on record in the stance chip above.
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