HPAP: High precision active probe for path round-trip delay measurement

Proposes a scheme to realize a high-performance communication facility using a commodity network. This scheme does not require any special hardware or hardware-specific device drivers in order to adapt to many kinds of network interface cards (NICs). In this scheme, a reliable lightweight network protocol is handled directly on a data link layer called by a network device driver. An interrupt reaping technique is proposed to eliminate the hardware interrupt overhead when an application waits for a message. PM/Ethernet, an instance of the scheme, is implemented on Linux with minimal modification to the Linux kernel, and existing network device drivers are used without any modification. Using Pentium III 500-MHz PCs on Packet Engine's G-NIC II Gigabit Ethernet NIC, it achieves 77.5 MB/s bandwidth and 37.6 /spl mu/s round-trip time latency compared to that of TCP/IP, which achieves 46.7 MB/s bandwidth and 89.6 /spl mu/s round-trip time latency. The NAS parallel benchmark IS results show that MPI on PM/Ethernet achieves 75% better performance than MPI on TCP/IP and is 7.8% slower than that of MPI on Myrinet PM.

Capacity estimation effective in an IP network path is a key enabling technology for proactive and reactive resource management as well as intelligent planning in next generation IP networks. We analyze capacity measurements at different Internet destinations. Particularly, we use the variable packet size (VPS) method to measure the per-hop capacity in some network paths. This method is based on round trip time (RTT) measurements as well as on the Internet control message protocol, ICMP. The RTT delay is approximated by a gamma distribution. We observe how the measurement accuracy of this active probing is affected by factors such as layer 2 device latencies, limited clock resolution at the probing host, or queuing delay. These factors cause non linearity on the RTT curves obtained and, consequently, inaccuracies on the estimation of path capacities. The use of robust regression to improve linear approximation in the VPS method is proposed. As a result, we obtain better qualitative and quantitative results.

Evaluating the Impact of Cyberattacks on PLC Performance: A Systematic Implementation and Empirical Investigation

In a communication network, transmission control protocol (TCP) is used to avoid congestion through which the sources with small round trip time (RTT) allocate the bottleneck link unfairly. On the other hand, the bottleneck link capacity is time-varying in wireless access networks due to the fading effects and errors in the acknowledgment packets. Therefore, queue management is more sophisticated in wireless networks than that in wired ones. Also, when the number of the sources changes, the network acts as a switched system in which non-zero initial values cause the response not to converge to the desired value. The main contribution of this paper is to design a switched rate-based robust queue management (SRRQM) to control the congestion contemporary with weighted fairness and maximum utilization compatible with wireless access networks. Moreover, a procedure called initial value compensation (IVC) is designed to overcome the non-zero initial value effects. Two degree of freedom multi-loop internal model (TDF-MIM) method is used for robust congestion control. The utilization factors are designated proportionally to user's RTT values to ensure weighted fairness and maximum utilization. To the authors' knowledge, this is the first time that a SRRQM is designed for a wireless access network with the advantages of weighted fairness, maximum utilization and robustness against capacity variation, PER and changing in the number of the sources. Analytical and simulation results demonstrate the efficacy of the proposed procedure.

The packet processing time (PPT) of an end host (i.e., workstation) is the time elapsed between the arrival of a packet at the data-link layer and the time the packet is processed at the application layer (RFCs 2679). A recent work presented an active scheme to measure PPT over Internet paths using a packet-pair based probing structure considering its importance as a network parameter in the Internet. However, the existing scheme does not consider the effect of interrupt coalescence (IC) in network interface cards (NICs), which are configured with an IC under high transmission speeds. In this paper, we propose an enhancement to the existing scheme for measuring PPT when there is an IC available in the NIC of the workstation under test. The enhanced scheme first detects IC and then measures PPT using the measured gaps of the probing structure. We evaluated the enhanced scheme through testbed experiments using two different workstations and under different transmission speeds, i.e., 10, 100, and 1000 Mb/s. Our results show that the proposed scheme consistently measures PPT with high efficacy.

Multi-homing is a common practice among many (especially large) customer (or stub) networks. Although the purpose of multi-homing is primarily for enhanced reliability, it has also increasingly been used for load balancing and latency reduction. In this paper, we address the problem of how to perform scalable route selection in a multi-homed stub network to optimize network latency to various destinations as measured by round-trip-time (RTT). A straight forward method is to simply perform RTT measurements (e.g., using ping) to each destination via each provider and select the one with the minimum RTT as the best next-hop to the destination. Is there a more.To answer this question, we carry out a measurement-based study to analyze the differences of RTTs in using two different providers in a multi-homed stub network to reach a large number of randomly selected destinations. Our study reveals that because of the AS hierarchy, for a large fraction of the network prefixes, the two AS paths through two providers merge in the core of the Internet. Furthermore, the router at which the two router level paths merge is actually in the AS at which the AS level paths merge. This phenomenon causes the RTT difference between the two paths through the two providers to be determined by the non shared portion of the paths. Our study reveals that most of the two router level paths through the two upstream providers merge at the AS at which the two AS level paths merge. Based on this finding, we devise a scalable route (next-hop provider) selection algorithm using BGP information in a multi-homed stub network. We also present a preliminary evaluation.

Abstract. Modern mobile devices offer advanced capabilities for navigation and Location-Based Services (LBS). This study investigates the use of Ultra-Wideband (UWB) and Wi-Fi Round-Trip Time (RTT) measurements for pedestrian localization across various scenarios. We analyze the ranging accuracy of these techniques and evaluate positioning performance using different fusion algorithms. Our proposed collaborative positioning (CP) methodology enhances localization accuracy for user groups within a defined area. Results demonstrate significant improvements in position trueness, with UWB and Wi-Fi RTT achieving enhancements of 74% and 54%, respectively. Additionally, our localization algorithm, leveraging a Peer-to-Infrastructure (P2I) and Peer-to-Peer (P2P) hybrid configuration, increases anchor availability by up to 10%. Even in short-duration anchor loss scenarios (P2P-only), position trueness improves by up to 53%. These findings highlight the potential of UWB and Wi-Fi RTT in real-world pedestrian localization, particularly for urban navigation, smart mobility applications, and emergency response systems.

This paper presents a performance analysis of data transfer and processing in a hardware accelerator using AXI DMA with various configurations, including single-core and multi-core designs, as well as single-clock and multiclock setups. The system utilizes DMA for data movement between DDR memory and programmable logic (PL), and the evaluation measures key performance metrics such as DDR send/receive times and DMA roundtrip latency. Experimental results show that the multiclock single-core design achieves better overall performance than the single-clock design, reducing roundtrip time from 4.811 ms to 3.331 ms due to faster memory transfer at 125 MHz. However, the increased processing latency in the PL, caused by downsampling logic, offsets some of the gains. Furthermore, while multi-core configurations are expected to accelerate processing, the dual-core design exhibits performance degradation due to software-level overhead in the processing system (PS), leading to the slowest roundtrip time of 4.131 ms. The triple-core design offers modest improvements <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(3.321 ~\text{ms})$</tex>, but still does not scale linearly. These findings suggest that efficient system-level integration and software optimization are crucial to fully leveraging hardware parallelism in PL-based acceleration architectures.

Grids offer the potential to carry out difficult computing tasks and achieve superior aggregate performance. However, grids are highly complex systems. They consist of heterogeneous resources on disparate hosts from various virtual organizations interconnected via a mixture of communication standards. Monitoring grid resources allows grid schedulers to adapt to changes in the status of these remote resources and the network paths between them. This is crucial to ensuring optimum performance. In this paper we introduce a distributed solution, called GridMAP, to collect network and end-host resource measurements, analyze their performance and feed these statistics and predictions back to schedulers. At this stage, we present our implementation of a passive TCP-SYN-based technique to provide GridMAP with round trip time and throughput measurements and we evaluate our approach against ping and iperf.

5G NR mm Wave promises accurate positioning down to the centimeter level. However, mmWave signals endure prismatic propagation, making them prone to signal blockages and non-line of sight (NLoS) communications. To achieve a precise positioning solution, it is rather essential to filter out NLoS gNBs as they yield erroneous pose estimation of IoT vehicular applications. Previous works have attempted to address this issue, however, they are either based on impractical or invalid assumptions about the operation scenario. In this paper, a novel, yet, simple and realistic NLoS detection algorithm is developed. The proposed method measures the discrepancy between Received Signal Strength (RSS)-based and time-based ranges as means to detect NLoS operation. To validate the proposed NLoS detection method, it was incorporated into a Kalman Filter (KF) that fuses the angle of departure (AoD) and round trip time (RTT) measurements from multiple gNBs in a loosely coupled fashion. The proposed method was evaluated on quasi-real measurements acquired from a highly validated 5G simulation tool that simulates the cores of downtown Toronto. The proposed method demonstrates superior results, as it sustains a sub-1m level of accuracy for around 95% of the time, as compared to merely 29% of the time without the NLoS detection.

A large amount of algorithms has recently been designed for the Internet under the assumption that the distance defined by the round-trip delay (RTT) is a metric. Moreover, many of these algorithms (e.g., overlay network construction, routing scheme design, sparse spanner construction) rely on the assumption that the metric has bounded ball growth or bounded doubling dimension. This paper analyzes the validity of these assumptions and proposes a tractable model matching experimental observations. On the one hand, based on Skitter data collected by CAIDA and King matrices of Meridian and P2PSim projects, we verify that the ball growth of the Internet, as well as its doubling dimension, can actually be quite large. Nevertheless, we observed that the doubling dimension is much smaller when restricting the measures to balls of large enough radius. Moreover, by computing the number of balls of radius r required to cover balls of radius R > r, we observed that this number grows with R much slower than what is predicted by a large doubling dimension. On the other hand, based on data collected on the PlanetLab platform by the All-Sites-Pings project, we confirm that the triangle inequality does not hold for a significant fraction of the nodes. Nevertheless, we demonstrate that RTT measures satisfy a weak version of the triangle inequality: there exists a small constant p such that for any triple u, v, w, we have RTT(u,v) les rho-max{RTT(u,w),RTT(w,v)}. (Smaller bounds on p can even be obtained when the triple u, v, w is skewed). We call inframetric a distance function satisfying this latter inequality. Inframetrics subsume standard metrics and ultrametrics. Based on inframetrics and on our observations concerning the doubling dimension, we propose an analytical model for Internet RTT latencies. This model is tuned by a small set of parameters concerning the violation of the triangle inequality and the geometrical dimension of the network. We demonstrate the tractability of our model by designing a simple and efficient compact routing scheme with low stretch. Precisely, the scheme has constant multiplicative stretch and logarithmic additive stretch.

Traditional rogue access-point (AP) detection mechanisms are employed in network administration to protect network infrastructure and organization; however, these mechanisms do not protect end users from connecting to a rogue-AP. In this paper, a rogue-AP detection technique on the mobile-user side is proposed. By using a simple method involving walking, the round-trip time (RTT) and the modulation and coding scheme values are obtained, and a more accurate transmission rate for particular RTT values is thereby calculated. Further, the cleansed data are classified using the k-means method and the cumulative distribution function for the detection process. The results demonstrate that a rogue-AP can be detected with an F-measure value of up to 0.9. In the future, the proposed algorithm can be implemented as an application installed on mobile devices so that nontechnical users can detect rogue-APs.

The General Packet Radio Service (GPRS) is being deployed by GSM network operators world-wide, and promises to provide users with “always-on” data access at bandwidths comparable to that of conventional fixed-wire telephone modems. However, many users have found the reality to be rather different, experiencing very disappointing performance when, for example, browsing the web over GPRS. In this paper, we examine the causes, and show how unfortunate interactions between the GPRS link characteristics and TCP/IP protocols lead to poor performance. A performance characterization of the GPRS link-layer is presented, determined through extensive measurements taken over production networks. We present measurements of packet loss rates, bandwidth availability, link stability, and roundtrip time. The effect these characteristics have on TCP behavior are examined, demonstrating how they can result in poor link utilization, excessive packet queueing, and slow recovery from packet losses. Further, we show that the HTTP protocol can compound these issues, leading to dire WWW performance. We go on to show how the use of a transparent proxy interposed near the wired-wireless border can be used to alleviate many of these performance issues without requiring changes to either client or server end systems.

Accurate human counting in indoor environments is essential for optimizing people-centric applications, such as crowd management, disaster response, and monitoring in settings like shopping malls and healthcare facilities. Traditional vision approaches face challenges with poor lighting conditions and raise privacy concerns. WiFi-based solutions enable device-free human counting by detecting disruptions in wireless signals caused by human presence. However, methods using received signal strength indicator are unreliable due to physical obstructions, multipath fading, radio interference, and fluctuating access point power. While WiFi channel state information-based systems are more sensitive to environmental changes, they lack standardization, limiting their practicality. To overcome these limitations, this paper presents Time4Count, an innovative device-free indoor human counting system that leverages round trip time measurements to achieve high accuracy and scalability. Time4Count capitalizes on human-induced fluctuations in signal propagation time to accurately estimate the number of individuals in a space. By employing a multivariate transformer-based feature extraction method, the system effectively mitigates non-line-of-sight errors and signal distortions, ensuring robust performance even in cluttered indoor environments. Additionally, Time4Count integrates spatial discretization and multi-label classification techniques, enabling it to count an unlimited number of individuals in real-time. The system was rigorously evaluated in two realistic, cluttered environments using commodity hardware, involving up to 15 participants. Experimental results reveal that Time4Count achieves an high counting accuracy of 92.7%. To our knowledge, Time4Count is the first RTT-based indoor counting system, providing a precise solution for indoor monitoring. Implementation is available at: https://github.com/mclab-osaka/time4count.

Monitoring Round-Trip Time provides important insights for network troubleshooting and traffic engineering. The common monitoring technique is to actively send probe packets from selected vantage points (hosts or middleboxes). In traditional networks, the control over the network routing is limited, making it impossible to monitor every selected path. The emerging concept of Software Defined Networking simplifies network control. However, OpenFlow, the common SDN protocol, does not support RTT monitoring as part of its specification. In this paper, we leverage the ability of OpenFlow to control the routing, and present GRAMI, the Granular RTT Monitoring Infrastructure. GRAMI uses active probing from selected vantage points for efficient RTT monitoring of all the links and any round-trip path between any two switches in the network. GRAMI was designed to be resource efficient. It requires only four flow entries installed on every switch in order to enable RTT monitoring of all the links. For every round-trip path selected by the user, it requires a maximum of two additional flow entries installed on every switch along the measured path. Moreover, GRAMI uses a minimal number of probe packets, and does not require the involvement of the controller during online RTT monitoring.