Search Results (17)

In recent years, the concentration risk of the Internet has intensified, with traffic being concentrated in the hands of a few service providers. However, existing research focuses on the client-side perspective and lacks a centralized measurement of the public resolver in terms of operation strategies and software functionality implementation. Therefore, we propose a dual-end measurement framework to measure the public resolver from both the client and authoritative perspectives, stably matching the active nodes of the public resolver pool with their providers, and using probes to evaluate the diversity of its functionality implementation and configuration schemes. The study analyzed the operation plans of different suppliers and revealed the regional nature of the public resolver service scope, enabling the localization of specific resolver instances, thereby achieving a concentration assessment for specific suppliers. In actual measurements from the perspectives of 5 countries and regions using 14 probes on 4 large public resolvers and 7 regional resolvers, we found that although anycast provides geographical redundancy, the software implementation logic of the public resolver cluster in a single region tends to be somewhat homogeneous. The characteristic entropy of Google in five regions was 1.435, while in the Silicon Valley region of the United States, there was only one software implementation. Full article

Distributed Denial-of-Service (DDoS) attacks remain the most pervasive and operationally disruptive cyber threat and are routinely weaponized in interstate conflict (e.g., Russia–Ukraine and Stuxnet). Although attack-chain models are standard for Advanced Persistent Threat (APT) analysis, they have seldom been applied to DDoS, which is often framed as a single-step volumetric assault. However, ubiquitous intelligence and ambient connectivity increasingly enable DDoS campaigns to unfold as multi-stage operations rather than isolated floods. In parallel, large language models (LLMs) create new opportunities to strengthen traditional DDoS defenses through richer contextual understanding. Reviewing incidents from 2019 to 2024, we propose a three-phase DDoS attack chain—preparation, development, and execution—that captures contemporary tactics and their dependencies on novel hardware, network architectures, and application protocols. We classify these patterns, contrast them with conventional DDoS, survey current defenses (anycast and scrubbing, BGP Flowspec, programmable data planes, adaptive ML detection, API hardening), and outline research directions in cross-layer telemetry, adversarially robust learning, automated mitigation orchestration, and cooperative takedown. Full article

The suspension arm is a crucial connecting component in the automotive powertrain system, required to withstand various working condition loads, thus necessitating high mechanical performance. With the continuous development of forming processes, the forming method of suspension arms has gradually shifted from traditional gravity casting to squeeze casting. Along with the demand for automotive lightweighting, there is an urgent need for lightweight requirements in suspension arm components. This study employs a multi-condition topology optimization method, incorporating the forming requirements of the squeeze casting process, to conduct lightweight design of a certain mounting bracket. The filling and solidification processes were numerically simulated using Anycasting, followed by mechanical property testing and microstructure analysis of the product. The results revealed that the topology-optimized suspension arm met the strength and stiffness requirements under all working conditions, with a mass reduction of approximately 54.7% compared to the pre-optimized version. Based on the forming process analysis of the suspension arm, the design of its squeeze casting mold was completed. Using AnyCasting software (AnyCasting 6.7), numerical simulations of the filling and solidification processes of the suspension arm were conducted. Combined with theoretical calculations, the forming process parameters for the suspension arm were finally determined as follows: extrusion speed of 15 cm/s-10 cm/s-5 cm/s (multi-stage speed), pouring temperature of 690 °C, mold temperature of 250 °C, extrusion pressure of 81.4 MPa, and holding time of 45 s. Through T6 heat treatment, the tensile strength, yield strength, and elongation after fracture of the suspension arm reached 326.05 MPa, 276.87 MPa, and 9.68%, respectively. Metallographic analysis showed that the eutectic silicon in the T6 heat-treated specimens was primarily spherical in shape, uniformly distributed without significant clustering. The reason for this difference may be that heat treatment affects the boundary dissolution degree of alloying elements. For eutectic Al-Si alloys, the boundary dissolution and diffusion of alloying elements are accelerated, which is beneficial for improving the mechanical properties of the alloy. Finally, in order to quantitatively analyze the microstructural properties of the material after heat treatment, analyses of secondary dendrite arm spacing and porosity were conducted, leading to the conclusion that the microstructure after heat treatment is more uniform and dense. Full article

Aluminum alloy die casting has achieved rapid development in recent years and has been widely used in all walks of life. However, due to its high pressure and high-speed technological characteristics, avoiding hole defects has become a problem of great significance in aluminum alloy die casting production. In this paper, the filling visualization dynamic characterization experiment was innovatively developed, which can directly study and analyze the influence of different injection rates on the formation and evolution of alloy flow patterns and gas-induced defects. As the injection speed increased from 1.0 m/s to 1.5 m/s, the average porosity increased from 7.49% to 9.57%, marking an increase in the number and size of the pores. According to the comparison with Anycasting, simulation results show that a liquid metal injection speed of 1.5 m/s when filling the flow front vs. the previous injection rate of 1.0 m/s caused fractures when filling at the same filling distance. Therefore, the degree of the broken splash at the flow front is more serious. Combined with the analysis of transport mechanics, the fracturing is due to the wall-attached jet effect of the liquid metal in the filling process. It is difficult for the liquid metal to adhere to the type wall in order to fuse with subsequent liquid metal to form cavity defects. With an increase in injection velocity, the microgroup volume formed via liquid breakage decreases; thus the volume of air entrapment increases, finally leading to an increase in cavity defects. Full article

Current cloud computing expects to face huge traffic costs, data loads, and high latency due to the explosion of data from devices as the IoT and 5G technology evolve. Fog computing has emerged to overcome these issues. It deploys small fog servers at the edge of the network to process critical data in real time while sending the remaining secondary tasks to the central cloud, instead of sending massive amounts of data to the cloud. With the rise in fog computing, among traditional security threats, distributed denial-of-service (DDoS) attacks have become the major threat to availability. This is especially true for fog computing, where real-time processing is critical; there are many fog servers, and the processing power is relatively low. Distributed reflection denial-of-service (DRDoS), one of the frequently used DDoS attack techniques, is an amplification attack that can be used on a small or large scale. It is widely used in attack tools due to its easy configuration. This study analyzes the characteristics of fog computing, the characteristics of DRDoS attacks, and the advantages and disadvantages of existing countermeasures. Based on these analyses, this study proposes a model that could effectively mitigate attacks even on low-specification fog servers by combining a modified Snort module with reduced functionality, simple pattern matching, and filtering distribution using Anycast. This mitigation algorithm has a simple structure rather than a complex filtering structure. To achieve this goal, this study virtually implemented the corresponding fog IoT environment. In spite of its simple structure, it proved that the fog server could secure availability even under DRDoS attacks by implementing and validating the mitigation model. Full article

In order to study the influence of impeller structural parameters on the hydraulic performance and casting moulding of spiral centrifugal pumps, this paper selects a double vane spiral centrifugal pump with a specific rotation number of 170 as the research object. The Plackett–Burman experimental design is used to screen the influencing factors, and the results show that the vane thickness and the impeller outlet width are the significant influencing factors. Based on this result, five different scenarios were set for these two key parameters, numerical calculations were carried out using numerical simulation software for each of the five flow ratio cases, and casting simulations were carried out for the model of each scenario using AnyCasting6.0 to analyze the influence of these two factors on the hydraulic performance and casting forming of the spiral centrifugal pump. It was found that in terms of vane thickness, a moderate increase in vane thickness improved the hydraulic performance at small flow rates, but an excessive increase at large flow rates led to a decrease in efficiency and an increase in the probability of casting defects. In terms of impeller outlet width, increasing the outlet width caused the design point to be shifted, leading to a decrease in efficiency at small flow rates, but an increase in efficiency when the design flow rate was higher. At the same time, increasing the outlet width makes casting defects more likely to occur at the blade and back cover joint than on the blade surface. The study in this paper clarifies the significant effects of these two parameters on the performance and casting quality of spiral centrifugal pumps, and provides guidance for the optimal design of spiral centrifugal pumps. Full article

The operation of today’s Internet can only be achieved with the domain name system (DNS), and the essential part of the DNS is the root servers. Adding anycast mirrors has been used to maintain the security of root servers, but many problems accompany this technique. In this paper, we used 36198 probe points deployed worldwide to probe 1160 root mirror sites and analyzed the data with root mirrors’ identification and localization (RMIL). RMIL is a method to identify and locate root mirrors. It contains probing and analyzing the network services ID (NSID) and traceroute data to identify and locate root mirror sites. Using this method, 821 (70.78% of the total) sites were accurately identified and located, and city-level localization was achieved for 281 other sites. Finally, the identification results were used in the service area analysis. The analysis contained multiple dimensions: locations, autonomous system numbers (ASN), internet service providers (ISP), and IPV4 prefixes. As such, we helped identify and locate root mirror sites more precisely and discover which ones have a greater service area in different dimensions. Full article

The wave field in solidifying metals is the theoretical basis for analyzing the effects of mechanical vibration on solidification, but there is little research on this topic. This study investigated the wave field and its effect on the solidification feeding in the low-pressure sand casting (LPSC) of Al-Cu-Mn-Ti alloy through experimental and numerical investigation. The solidification temperature field was simulated by Anycasting^TM, and the wave field was simulated by the self-developed wave propagation software. The shrinkage defect detection showed that applying vibration had a greater promotional effect on feeding than increasing the holding pressure. The predicted defects under vibration coincided with the detections. The displacement field showed that the casting vibrated harmonically with an inhomogeneous amplitude distribution under the continuous harmonic vibration excitation, and the vibration energy was mainly concentrated in the feeding channel. With solidification, the $u_x$ amplitude reduced rapidly after the overlapping of dendrites, finally reducing slowly to a certain level; the $u_y$ amplitude reduced dramatically after the occurrence of a quasi-solid phase, finally reducing slowly to near zero. Mechanical vibration produced a severe shear deformation in the quasi-liquid phase—especially in the lower feeding channel—reducing the grain size to promote mass feeding. The feeding pressure and feeding gap were changed periodically under vibration, causing the vibration-promoting interdendritic feeding rate to fluctuate and eventually stabilize at about 13.4%. The mechanical vibration can increase the feeding pressure difference and change the blockage structure simultaneously, increasing the formation probability of burst feeding. Full article

Modern internet of things (IoT) applications can benefit from advanced communication paradigms, including multicast and anycast. Next-generation internet architectures, such as information-centric networking (ICN), promise to support these paradigms, but at the same time they introduce new security challenges. This paper presents a solution that extends an ICN-like architecture based on software-defined networking (SDN) that supports those communication paradigms. Using the proposed solution, the underlying architecture is enhanced with a novel security mechanism that allows content “advertisements” only from authorized endpoints. This mechanism prevents “content pollution”, which is a significant security threat in ICN architectures. The proposed solution is lightweight, and it enables identity sharing as well as secured and controlled identity delegation. Full article

Wireless sensor networks (WSN) can accurately and timely obtain the production information of crops, and provide data basis for intelligent agriculture. The dynamic crop state and unstable climate environment make it difficult to predict the connectivity probability of wireless links. Therefore, this paper studies an energy-saving opportunity routing transmission strategy under the influence of dynamic link interaction. The protocol establishes an importance model based on algebraic connectivity to reduce the energy consumption of network key nodes. At the same time, based on the improved Bellman–Ford algorithm, a method of constructing candidate sets is studied. It converts the opportunistic routing transmission cost of farm WSN into anycast link cost and the remaining opportunistic path cost affected by energy consumption. The priority queue is used to determine the nodes participating in the iteration, thereby reducing the computational overhead. The protocol also designs a backoff strategy considering the current residual energy to select the only forwarding node and reduce the unnecessary packet copies in the transmission process. Simulation results show that the studied method is superior to the existing opportunistic routing schemes in terms of packet overhead, network lifetime, energy consumption, and packet delivery rate. Full article

The root server is at the top of the domain name hierarchical structure. To improve root service performance, each root deploys anycast nodes worldwide. What is the actual service performance of these nodes after deployment? We analyze the service performance of the root anycast nodes deployed in China based on the active measurement data detected by the VPs of different ISPs in different geographical locations. From the analysis, we find that the resolution performance of the roots with anycast nodes deployed in China is higher than that of roots without deployment. However, users of different operators have significant differences in accessing the root servers, such as parsing time, hitting anycast nodes, and most anycast nodes only providing services for one operator, limiting the service scope and reducing the service performance. The analysis results can help the root management and introduction institutions master the actual service status of the root servers, which can be used to optimize the performance of the existing root anycast nodes and provide a basis for deploying new root anycast nodes in the next step. Finally, we find that 67 top-level domain names are hijacked on the resolution path based on the measured data. Full article

A cognitive networking approach to the anycast routing problem for delay-tolerant networking (DTN) is proposed. The method is suitable for the space–ground and other domains where communications are recurrently challenged by diverse link impairments, including long propagation delays, communication asymmetry, and lengthy disruptions. The proposed method delivers data bundles achieving low delays by avoiding, whenever possible, link congestion and long wait times for contacts to become active, and without the need of duplicating data bundles. Network gateways use a spiking neural network (SNN) to decide the optimal outbound link for each bundle. The SNN is regularly updated to reflect the expected cost of the routing decisions, which helps to fine-tune future decisions. The method is decentralized and selects both the anycast group member to be used as the sink and the path to reach that node. A series of experiments were carried out on a network testbed to evaluate the method. The results demonstrate its performance advantage over unicast routing, as anycast routing is not yet supported by the current DTN standard (Contact Graph Routing). The proposed approach yields improved performance for space applications that require as-fast-as-possible data returns. Full article

This paper proposed a “Probabilistic and Deterministic Tree-based Routing for WSNs (PDTR)”. The PDTR builds a tree from the leaves to the head (sink), according to the best elements in the initial probabilistic routing table, measured by the product of hops-count distribution, and transmission distance distribution, to select the best tree-paths. Each sender node forwards the received data to the next hop via the deterministic built tree. After that, when any node loses of its energy, PDTR updates the tree at that node. This update links probabilistically one of that node’s children to a new parent, according to the updated probabilistic routing table, measured by the product of the updated: Hops-count distribution, transmission distance distribution, and residual energy distribution at the loss of ${\ell }_e$ energy. By implementing the control parameters in each distribution, PDTR shows the impact of each distribution in the routing path. These control parameters are oriented by the user for different performances. The simulation results prove that selecting the initial best paths to root the packets via unicast, then improving the tree at the node with loss of energy by rooting the packets via anycast, leads to better performance in terms of energy consumption and network lifetime. Full article

Wireless sensor networks employ duty-cycles to save energy, with the cost of enlargement of end-to-end latency. Cross-layer protocols that use anycast medium access control achieve latency reduction in asynchronous duty-cycled wireless sensor networks (WSNs). A series of strobed preambles is sent in order to achieve rendezvous with the next relay, selected from a forwarding candidate set (FCS). This paper proposes PAX-MAC: Pramble Ahead Cross-layer Medium Access Control. It is a novel anycast protocol for low latency packet propagation in duty-cycled WSNs. In PAX-MAC, preambles propagate ahead of data packet, prospecting the route towards sink node, while the message is sent some hops later. Simultaneous propagation of preambles and data packets provides latency reduction. The cardinality of FCS determines the average preamble propagation speed, which is lower bounded by data packet propagation speed. Differently from other approaches, our protocol takes the data packet size into account in order to maintain an optimal distance between preamble and data to minimize latency. For determining this distance, a detailed mathematical model is introduced. The performance of several state-of-the-art asynchronous protocols was appraised and compared with PAX-MAC. Our protocol outperforms in latency all other protocols for the simulated scenarios. Its energy expenditure was compatible with the best result among the other protocols. In the worst case, PAX-MAC spent $6\%$ more energy than the best one for a gain of $20\%$ in latency. Full article

Although numerical simulation accuracy makes progress rapidly, it is in an insufficient phase because of complicated phenomena of the filling process and difficulty of experimental verification in high pressure die casting (HPDC), especially in thin-wall complex die-castings. Therefore, in this paper, a flow visualization experiment is conducted, and the porosity at different locations is predicted under three different fast shot velocities. The differences in flow pattern between the actual filling process and the numerical simulation are compared. It shows that the flow visualization experiment can directly observe the actual and real-time filling process and could be an effective experimental verification method for the accuracy of the flow simulation model in HPDC. Moreover, significant differences start to appear in the flow pattern between the actual experiment and the Anycasting solution after the fragment or atomization formation. Finally, the fast shot velocity would determine the position at which the back flow meets the incoming flow. The junction of two streams of fluid would create more porosity than the other location. There is a transition in flow patterns due to drag crisis under high fast shot velocity around two staggered cylinders, which resulted in the porosity relationship also changing from R1 < R3 < R2 (0.88 m/s) to R1 < R2 < R3 (1.59 and 2.34 m/s). Full article