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MQTT, a popular IoT messaging protocol, is frequently associated with numerous vulnerabilities, the majority of which are critical. Many IoT devices that utilize MQTT are susceptible to cyberattacks such as denial-of-service and buffer overflow. In this paper, we unveil a novel Denial of Service (DoS) attack in the MQTT protocol, referred to as Slow Subscribers, which has the potential to cause MQTT brokers to become single points of failure. Unlike existing MQTT DoS attacks, Slow Subscribers can occur on a single compromised node and could potentially disrupt a MQTT broker with minimal subscription permissions. We evaluated the reliability of Mosquitto and NanoMQ, two popular MQTT messaging brokers, to determine the effect of Slow Subscribers. According to the findings of our investigation, NanoMQ outperforms Mosquitto in response to the Slow Subscribers attack at QoS level 0. We also determine that the response to Slow Subscribers at QoS 2 is the worst for both broker implementations. In addition, the results of our experiments indicate that Eclipse Mosquitto achieves a higher rate of reliability than NanoMQ on cloud deployments whereas NanoMQ has proven to be well-suited for edge environments, especially edge IoT devices that require the use of QoS levels 0 and 1. Finally, we propose a Resilient Middleware for Message Queue Telemetry Transport (Remistry) framework that is capable of detecting misconfigurations while providing granular support of resource commitment errors, in particular the out-of-memory (OOM) problems for effectively mitigating the impact of Slow Subscribers attacks on MQTT brokers. [ABSTRACT FROM AUTHOR]

Internet of Things (IoT) paved the way for devices and machine communication using TCP/IP protocol. Lightweight and stateless communication is imperative especially in a situation requiring conservation of energy usage, e.g. wireless sensor network. Representational State Transfer (REST) API method is based on web communication protocol, Hyper-Text Transfer Protocol (HTTP), and is widely used in IoT messaging. Some of these protocols are DPWS, XMPP, MQTT, COaP, AMQP. Among these protocols, MQTT is the most preferred protocol and is expected to be the de facto messaging IoT standard. MQTT uses a publisher/subscriber model to facilitate messaging between devices making messaging lightweight. Nevertheless, there are a number of security issues due to the design of the protocol itself. Some of the issues are denial of service, identity spoofing, information disclosure, elevation of privileges and data tampering. These issues can be caused by both internal and external perpetrators. Researchers have proposed various security techniques and mechanisms to address these issues. Incorporation of security has added processing overhead to the devices and this will have a bearing on IoT devices that are powered by a battery. This issue has opened up new research challenges in making the protocols more lightweight and at the same time not compromising the level of security provided. [ABSTRACT FROM AUTHOR]

Middlewares are standard tools for modern software development in many areas, especially in robotics. Although such have become common for high-level applications, there is little support for real-time systems and low-level control. Therefore, µRT provides a lightweight solution for resource-constrained embedded systems, such as microcontrollers. It features publish–subscribe communication and remote procedure calls (RPCs) and can validate timing constraints at runtime. In contrast to other middlewares, µRT does not rely on specific transports for communication but can be used with any technology. Empirical results prove the small memory footprint, consistent temporal behavior, and predominantly linear scaling. The usability of µRT was found to be competitive with state-of-the-art solutions by means of a study.

Abstract Background The Internet of Things (IoT) enables the development of innovative applications in various domains such as healthcare, transportation, and Industry 4.0. Publish-subscribe systems enable IoT devices to communicate with the cloud platform. However, IoT applications need context-aware messages to translate the data into contextual information, allowing the applications to act cognitively. Besides, end-to-end security of publish-subscribe messages on both ends (devices and cloud) is essential. However, achieving security on constrained IoT devices with memory, payload, and energy restrictions is a challenge. Contribution Messages in IoT need to achieve both energy efficiency and secure delivery. Thus, the main contribution of this paper refers to a performance evaluation of a message structure that standardizes the publish-subscribe topic and payload used by the cloud platform and the IoT devices. We also propose a standardization for the topic and payload for publish-subscribe systems. Conclusion The messages promote energy efficiency, enabling ultra-low-power and high-capacity devices and reducing the bytes transmitted in the IoT domain. The performance evaluation demonstrates that publish-subscribe systems (namely, AMQP, DDS, and MQTT) can use our proposed energy-efficient message structure on IoT. Additionally, the message system provides end-to-end confidentiality, integrity, and authenticity between IoT devices and the cloud platform.

Security attacks on Cyber-Physical Systems with operations that involve Unmanned Aerial Vehicles (UAVs) are a matter of great concern due to their major impact in the deployed systems, and a deal-breaker for their utilization; if a system is not perceived as secure, either it will not be used or its capabilities will be underutilized, regardless of how good they could be. This happens with particular intensity in missions with UAVs, as they can be hacked to tamper with their collected data or taken away by unauthorized parties. Development of security countermeasures is extensive both in theoretical and practical implementations, but the integration of these measures can be difficult, and performance might be affected because of it. This manuscript puts forward a SEDIBLOFRA (Secure, Distributed, Blockchain-based Framework) for remote maneuvering of UAVs, based on several distributed systems technologies that pile up to provide complementary functionalities. Asymmetric cryptography encrypts the data. Publish/Subscribe communications offer a way to enhance data delivery. Finally, blockchain provides a way to keep all the transferred data in a redundant and immutable manner. The proposed framework is also extensible to other kinds of unmanned vehicles, like Unmanned Ground Vehicles or Autonomous Underwater Vehicles.

Background: The Internet of Things (IoT) enables the development of innovative applications in various domains such as healthcare, transportation, and Industry 4.0. Publish-subscribe systems enable IoT devices to communicate with the cloud platform. However, IoT applications need context-aware messages to translate the data into contextual information, allowing the applications to act cognitively. Besides, end-to-end security of publish-subscribe messages on both ends (devices and cloud) is essential. However, achieving security on constrained IoT devices with memory, payload, and energy restrictions is a challenge. Contribution: Messages in IoT need to achieve both energy efficiency and secure delivery. Thus, the main contribution of this paper refers to a performance evaluation of a message structure that standardizes the publish-subscribe topic and payload used by the cloud platform and the IoT devices. We also propose a standardization for the topic and payload for publish-subscribe systems. Conclusion: The messages promote energy efficiency, enabling ultra-low-power and high-capacity devices and reducing the bytes transmitted in the IoT domain. The performance evaluation demonstrates that publish-subscribe systems (namely, AMQP, DDS, and MQTT) can use our proposed energy-efficient message structure on IoT. Additionally, the message system provides end-to-end confidentiality, integrity, and authenticity between IoT devices and the cloud platform. [ABSTRACT FROM AUTHOR]

Multiagent Systems (MASs) have multiple different characteristics, such as autonomy, and asynchronous and social features, which make these systems difficult to understand. Thus, there is a lack of procedures guaranteeing that multiagent systems once implemented would behave as desired. Determining the reliability of such systems is further complicated by the fact that current agent-based approaches may also involve non-deterministic characteristics, such as learning, self-adaptation and self-organization (SASO). Nonetheless, there is a gap in the literature regarding the testing of systems with these features. This paper presents an approach based on metadata and the publish-subscribe paradigm to develop test applications that address the process of failure diagnosis in a self-organizing MAS. The novelty of the proposed approach involves its ability to test self-organizing MAS systems in the context of local and global behavior. To illustrate the use of this approach, we developed a self-organizing MAS system based on the Internet of Things (IoT), which simulates a set of smart street lights, and we performed functional ad-hoc tests. The street lights need to interact with each other in order to achieve the global goals of reducing energy consumption and maintaining the maximum value of visual comfort in illuminated areas. To achieve these global behaviors, the street lights develop local behaviors automatically through a self-organizing process based on machine-learning algorithms.

Decentralized Identifiers (DIDs) are new self-manageable means of authentication, which is currently under standardization by the World Wide Web Consortium (W3C). Closely related to DIDs, verifiable credentials (VCs) are another ongoing standardization effort (by the same W3C working group) that enables privacy-preserving and cryptographically secure proofs of attribute ownership. Both these approaches assume in their core an immutable decentralized registry (e.g., a blockchain, or a p2p network) in which critical meta-data is recorded. However, W3C’s standards do not specify how this registry is implemented, instead this is left as an open implementation choice. In this paper we design, implement, and evaluate a secure DID/VC registry service using the emerging paradigm of Information Centric Networking (ICN). In order to achieve our goal, we combine the decentralized nature, and the “lookup by name” property of ICN, with a secure mechanism for maintaining synchronized replicas of an item in multiple locations. Due to ICN’s inherent support for multicast and caching, our construction imposes small network overhead, and achieves low lookup times.

The publish/subscribe paradigm provides a loosely-coupled and scalable communication model for the large-scale IoT service systems, such as supervisory control and data acquisition (SCADA). Data confidentiality and service privacy are two crucial security issues for the publish/subscribe model deployed in different domains. The existing access control schemes for such model cannot address both the issues at the same time. In this paper, we propose a comprehensive access control framework (CACF) to bridge this gap. The design principle of the proposed framework is twofold: (a) a bi-directional policy matching scheme for protecting the privacy of IoT services; and (b) a fully homomorphic encryption scheme for encrypting published events to protect data confidentiality. We analyze the correctness and security of the CACF, moreover, we prototype CACF based on Apache ActiveMQ, an open source message broker, and evaluate its performance. The experimental results indicate that our security system meets the latency requirements for very high-quality SCADA services.

Security in the Internet of Things is a current hot topic and it may comprise different aspects such as confidentiality and integrity of personal data, as well as the authentication and the authorization to access smart objects that are spreading more and more in our every-day lives. In this work we focus on MQTT (Message Queue Telemetry Transport), a message-based communication protocol explicitly designed for low-power machine-to-machine communications and based on the publish-subscribe paradigm. First of all, we provide an accurate analysis of some of the most recent security solutions and improvements of MQTT found in the literature. Secondly, we describe in detail a novel secure solution, called MQTT-Auth, to protect specific topics in MQTT. This solution is based on the AugPAKE security algorithm for guaranteeing confidentiality, and onto two tokens which permit to authenticate the usage of a topic and to guarantee authorization in accessing a topic respectively. MQTT-Auth can also be easily extended to a hierarchical structure of topics and entities. Finally, we compare MQTT-Auth with some solutions for securing MQTT being present in the relevant literature, and we provide some details on how MQTT-Auth has been implemented and successfully tested.

The publish-subscribe programming model has been an alternative to the design of data-intensive distributed applications in many domains. Recently, this model has been ported to the domain of Multiprocessor Systems-on-Chips, in which applications must use the underlying Network-on-Chip communication infrastructure effectively due to restrictions on the architecture such as low power consumption and limited memory size. In such a scenario, the publish-subscribe model fulfills some of these requirements while providing high-level access to the network hardware to programmers, thus contributing to software quality. However, the publish-subscribe model relies on a single process dedicated to orchestrating the communication at the application level, the broker. Should a broker process crash, the communication between associated nodes may experience delays, downtime, or even inconsistent data. In extreme cases, communication is definitively ruined. Thus, a recovery strategy for brokers in the publish-subscribe model becomes crucial when the application has safety requirements. In this work, we extend a publish-subscribe protocol to add redundancy to brokers' sensitive data. Besides, we provide a recovery protocol to recover brokers in case of a failure. We also provide analytical models to estimate the communication overhead of our approach. We validate our approach in two distinct MPSoC platforms. The results show that our approach inserts a small memory footprint to the system while providing minimal system downtime during recovery. [ABSTRACT FROM AUTHOR]

Intelligent environments combine physical spaces with pervasive computing technologies to provide context-aware, people-centred, and ambient-assisted strengthening of the activities of inhabitants in their daily lives. We propose a system to support mountain rescuers in their daily tasks. The system explores the activities of the mountain hikers, by analyzing data gathered from wireless sensor and mobile networks which cooperatively monitor an environment. The system utilizes message streaming brokers to transport data within the system. Massive amounts of data are pre-processed into formats, to allow analysis by logical SAT solvers. Pairing brokers and solvers as advanced technologies is challenging. The processed data contains valuable information about human activities and context situations, providing a basis for context reasoning and prediction. The resulting pro-active, hierarchical, and real-time smart decisions provide warnings about threatening situations, making tourists' stays safer. This combination of acting on predicted context, data streaming platforms, and logical solvers is a novel and innovative aspect of this approach. This strictly modeled system, intensively experimented, allows us to bridge the gap between the low-level observations produced by mobile and sensor networks and the high level smart services which support human activities.

Message Queuing Telemetry Transport (MQTT) is a widespread protocol for topic-based publish-subscribe architectures supporting IoT and social networks applications. MQTT brokers are logical entities that couple publishers and subscribers and play a critical role in such architectures. MQTT brokers can be implemented either as standalone servers or in a cluster configuration. Clusters of brokers increase reliability, availability and overall performance, since operations can be highly parallelized among the brokers that form the cluster. The load-balancing strategy in a cluster usually consists in connecting an incoming client to a randomly selected broker. This random-attach strategy, it is very simple, but generates a significant amount of inter-broker traffic, as we demonstrate through theoretical and experimental evaluations. Inter-broker traffic is an overhead for the system and it increases the CPU load of the brokers, compromising the scaling behavior of the whole cluster. Indeed, we found that a linear increase of the number of brokers forming a cluster does not necessarily provide an equivalent linear gain in performance, and such a scaling penalty can be surprisingly significant, in the order of 40%. To solve this issue and improve performance, we propose a novel load-balancing strategy that envisages the use of multiple MQTT sessions per client to reduce inter-broker traffic and that can be implemented by means of a greedy algorithm. We show feasibility and effectiveness of our strategy for IoT and social-network applications by means of simulations and real measurements. The resulting scaling penalty is reduced to 10%. [ABSTRACT FROM AUTHOR]

Fog computing dramatically extends the cloud computing to the edge of the network and admirably solves the problem that the brokers (in publish-subscribe system) generally lack of computing capacity and energy power. However, brokers may be disguised, hacked, sniffed, and corrupted. The traditional security technology cannot protect the system privacy when facing a possible collusion attack. In this paper, we propose a privacy-preserving content-based publish/subscribe scheme with differential privacy in fog computing context, named PCP, where the fog nodes act as the brokers. Specifically, PCP firstly utilizes the U-Apriori algorithm to mine the top-K frequent itemsets (i.e., the attributes) from uncertain data sets, then applies the exponential and Laplace mechanism to ensure the differential privacy, and the broker uses the mined top-K itemsets to match appropriate publisher and subscriber finally. Security analysis shows that the PCP can guarantee differential privacy in theory. To evaluate the performance of PCP, we carry out experiments with real-world scenario data sets. The experimental results show that PCP efficiently achieves the tradeoff between the system cost and the privacy demand.

Many data processing systems are naturally modeled as pipelines, where data flows though a network of computational procedures. This representation is particularly suitable for computer vision algorithms, which in most cases possess complex logic and a big number of parameters to tune. In addition, online vision systems, such as those in the industrial automation context, have to communicate with other distributed nodes. When developing a vision system, one normally proceeds from ad hoc experimentation and prototyping to highly structured system integration. The early stages of this continuum are characterized with the challenges of developing a feasible algorithm, while the latter deal with composing the vision function with other components in a networked environment. In between, one strives to manage the complexity of the developed system, as well as to preserve existing knowledge. To tackle these challenges, this paper presents EPypes, an architecture and Python-based software framework for developing vision algorithms in a form of computational graphs and their integration with distributed systems based on publish-subscribe communication. EPypes facilitates flexibility of algorithm prototyping, as well as provides a structured approach to managing algorithm logic and exposing the developed pipelines as a part of online systems.

Secure authentication while communicating data between sender and receiver nodes is a key concept when providing Internet of Things as a service. Hash algorithms can provide such an authentication mechanism for IoT based applications. The most recent secure hash algorithm technique standardized by the NIST is SHA-3. SHA-3 is fully apt in ensuring authentication for a sender and receiver transaction. A novel signature generating technique based on SHA-3 is presented in the paper. Two of the popular IoT communication models of publish subscribe and request response are examined under this authentication scheme. The sender generates a unique hash code for the data that it is about to send. This hash code serves as the authenticating token for the transaction. Mechanisms for the sender receiver interaction are built into the program codes in both the simulated communication models. The system architecture also manages interaction of the receiver with the cloud. This interaction ensures proper authentication through the mechanisms and api(s) provided by the cloud service providers, and these mechanisms are also integrated into the simulation. Both the cloud services used in the system architecture, i.e. cloud messaging as a service, and cloud database as a service ensure that the sender's identity is verified. In this way a blanket authentication system is set up for the aforementioned IoT architectures. [ABSTRACT FROM AUTHOR]

An Internet of Things (IoT) middleware can solve interoperability problem among "things" in IoT infrastructure by collecting data. However, the sensor nodes' data that is collected by the middleware cannot be directly delivered to cloud applications since the sensor nodes and the middleware are located in intranet. A solution to this problem is an Internet Gateway Device (IGD) that retrieves data from the middleware in intranet then forwards them to cloud applications in the internet. In this study, an IGD based on cellular network is proposed to provide wide-coverage internet connectivity. Two test scenarios were conducted to measure delay and throughput between the IGD and the cloud application; using data from DHT22 sensor and image sensor respectively. The results of the first test scenario using DHT22 sensor show that the average delay is under 5 seconds and the maximum throughput is 120 bps, while the second one using image sensor concludes that the average delay is 595 seconds and the maximum throughput is 909 bps. [ABSTRACT FROM AUTHOR]

We propose a holistic Model‐Based Protocol Specification (MBPS) framework. Standards, procedures, and protocols are important anchors for interconnected systems: they facilitate the connectivity of billions of devices around the world, commodify advanced technologies and solutions, and enable efficient services involving trillions of transactions in aviation, medicine, e‐commerce, transportation, infrastructure, and other domains. Domain protocols allow for conventional interactions within a domain among ecosystem entities and humans (eg, airline ticketing, financial transactions, etc). Protocol specifications must be formal, consistent, and verifiable. Nevertheless, most current standard protocols are text‐based, unverifiable, and often inconsistent with themselves and with other standards. Text‐based standards are difficult to manage, track, control, and adopt. MBPS includes three critical enablers: a modeling language, a modeling process, and a model‐supported standardization process. This paper employs Object‐Process Methodology (OPM), a model‐based systems engineering framework, endorsed as ISO‐19450, for modeling and simulation of the generic protocol specification process and for two examples: (a) a Kerberos authentication protocol revision based on a previous Kerberos model and on a recently discovered vulnerability and (b) a domain‐specific Publish—Subscribe protocol application for selective information distribution. [ABSTRACT FROM AUTHOR]

Communications systems and protocols are becoming second nature to utilities operating distribution systems. Traditionally, centralized communication approaches are often used, while recently in microgrid applications, distributed communication, and control schema emerge offering several advantages such as improved system reliability, plug-and-play operation, and distributed intelligence. Still, operation and control of microgrids including distributed communication schema have been less of a discussion in the literature. To address the challenge of multiple-inverter microgrid synchronization, a publish-subscribe protocol based, data distribution service, communication schema for microgrids is proposed. The communication schema is discussed in details for individual devices such as generators, photovoltaic systems, energy storage systems, microgrid point of common coupling switch, and supporting applications. Finally, islanding and resynchronization of a microgrid are demonstrated on a test-bed utilizing this schema. [ABSTRACT FROM AUTHOR]

Security in the Internet of Things is a current hot topic and it may comprise different aspects such as confidentiality and integrity of personal data, as well as the authentication and the authorization to access smart objects that are spreading more and more in our every-day lives. In this work we focus on MQTT (Message Queue Telemetry Transport), a messagebased communication protocol explicitly designed for low-power machine-to-machine communications and based on the publishsubscribe paradigm. First of all, we provide an accurate analysis of some of the most recent security solutions and improvements of MQTT found in the literature. Secondly, we describe in detail a novel secure solution, called MQTT-Auth, to protect specific topics in MQTT. This solution is based on the AugPAKE security algorithm for guaranteeing confidentiality, and onto two tokens which permit to authenticate the usage of a topic and to guarantee authorization in accessing a topic respectively. MQTT-Auth can also be easily extended to a hierarchical structure of topics and entities. Finally, we compare MQTT-Auth with some solutions for securing MQTT being present in the relevant literature, and we provide some details on how MQTT-Auth has been implemented and successfully tested. [ABSTRACT FROM AUTHOR]

In recent years we have been assisting a radical change in the way devices are connected to the Internet. In this new scope, the traditional TCP/IP host-centric network fails in large-scale mobile wireless distributed environments, such as IoT scenarios, due to node mobility, dynamic topologies and intermittent connectivity, and the Information-Centric Networking (ICN) paradigm has been considered the most promising candidate to overcome the drawbacks of host-centric architectures. Despite bringing efficient solutions for content distribution, the basic ICN operating principle, where content must always be associated with an interest, has serious restrictions in IoT environments in relation to scale, performance, and naming, among others. To address such drawbacks, we are presenting ndnIoT-FC, an NDN-based architecture that respects the ICN rules but offers special treatment for IoT traffic. It combines efficient hybrid naming with strategies to minimize the number of interests and uses caching strategies that virtually eliminates copies of IoT data from intermediate nodes. The ndnIoT-FC makes available new NDN-based application-to-application protocol to implement a signature model operation and tools to manage its life cycle, following a publisher-subscriber scheme. To demonstrate the versatility of the proposed architecture, we show the results of the efficient gathering of environmental information in a simulation environment considering different and distinct use cases.

Data Distribution Service (DDS) has emerged as a potential solution for data communication challenges in smart grids. DDS is designed to support quality communication for large scale real-time systems through a wide range of QoS policies. However, a smart grid involves various types of communication applications running on different computing environments. Some environments have limited computing resources such as small memory and low performance, which makes it difficult to accommodate DDS. In this paper, we present a feature-based approach for tailoring DDS to configure lightweight DDS by selecting only the necessary features for the application in consideration of the resource constraints of its running environment. This allows DDS to serve as a uniform communication middleware across the smart grid, which is critical for interoperability. We analyze DDS in terms of features and design them using Unified Modeling Language (UML) and Object Constraint Language (OCL) based on inheritance and overriding. We define a formal notion of feature composition to build DDS configurations. We implemented the approach in OpenDDS and demonstrate its application to different application environments. We also experimented the approach for the efficiency of configured DDS in terms of resource utilization. The results show that configured DDS is viable for efficient and quality data communication for applications that run on an environment with limited computing capability.

This paper introduces and validates through simulations, the concept of cooperative planning of intermodal operations. Using a publish-subscribe approach, vehicles coordinate their arrivals at the terminal to reduce the formation of queues, while the terminal use policies to reward cooperative behaviour. The simulation results are analysed in terms of service rates, delays, and queue sizes at terminals, and is compared to impact on queues of non-cooperative approaches. The proposed approach is expected to influence the functionality of autonomous vehicles in transport logistics, in the future. [ABSTRACT FROM AUTHOR]

Security and comfort become very important for every educational institution, especially college. Security and comfort should be properly integrated to create an ideal academic atmosphere. This research designs online security monitoring system of G4 TEUM's hallway area by utilizing social media using adaptive Publish Subscribe system. Publisher i.e. students upload the current condition of the G4 TEUM's hallway by utilizing social media: twitter, facebook or instagram, then brokers choose the uploaded data corresponding to G4 content to be sent in the form of notification to subscriber, which is TEUM security in the form of dynamic web application. The experimental results show that by using adaptive Publish-Subscribe method, the cpu usage is reduced by 31,76% and bandwith usage by 39,4%, compared with non-adaptive method, on data event obtained by both publisher and subscribe. Rasa aman dan nyaman merupakan salah satu hal yang sangat berpengaruh pada dunia pendidikan dalam pembelajaran, khususnya di perguruan tinggi. Keamanan dan kenyamanan harus diintegrasikan dengan baik untuk menciptakan atmosfer akademik yang ideal. Penelitian ini merancang sistem pemantauan keamanan online di area selasar G4 TEUM dengan memanfaatkan media sosial yang menggunakan sistem Publish-Subscribe Adaptif. Publisher yaitu mahasiswa mengunggah kondisi terkini dari selasar G4 TEUM dengan memanfaatkan media sosial, seperti twitter, facebook, dan instagram, kemudian broker memilih data upload sesuai dengan konten G4 yang akan dikirimkan berupa notifikasi ke Subscriber, yaitu pihak keamanan TEUM dalam bentuk aplikasi web dinamis. Hasil percobaan menunjukkan bahwa dengan menggunakan metode Publish-Subscribe adaptif, penggunaan CPU berkurang sebesar 31,76% dan penggunaan bandwidth sebesar 39,4%, dibandingkan dengan metode non adaptif, pada data event yang diperoleh baik pada Publisher maupun Subscriber.

Most industrial and SCADA-like (supervisory control and data acquisition) systems use proprietary communication protocols, and hence interoperability is not fulfilled. However, the MODBUS TCP is an open de facto standard, and is used for some automation and telecontrol systems. It is based on a polling mechanism and follows the synchronous request–response pattern, as opposed to the asynchronous publish–subscribe pattern. In this study, polling-based and event-based protocols are investigated to realize an open and interoperable Industrial Internet of Things (IIoT) environment. Many Internet of Things (IoT) protocols are introduced and compared, and the message queuing telemetry transport (MQTT) is chosen as the event-based, publish–subscribe protocol. The study shows that MODBUS defines an optimized message structure in the application layer, which is dedicated to industrial applications. In addition, it shows that an event-oriented IoT protocol complements the MODBUS TCP but cannot replace it. Therefore, two scenarios are proposed to build the IIoT environment. The first scenario is to consider the MODBUS TCP as an IoT protocol, and build the environment using the MODBUS TCP on a standalone basis. The second scenario is to use MQTT in conjunction with the MODBUS TCP. The first scenario is efficient and complies with most industrial applications where the request–response pattern is needed only. If the publish–subscribe pattern is needed, the MQTT in the second scenario complements the MODBUS TCP and eliminates the need for a gateway; however, MQTT lacks interoperability. To maintain a homogeneous message structure for the entire environment, industrial data are organized using the structure of MODBUS messages, formatted in the UTF-8, and then transferred in the payload of an MQTT publish message. The open and interoperable environment can be used for Internet SCADA, Internet-based monitoring, and industrial control systems.

Smart grid has emerged as the next generation of power grids for improved control and efficiency of power production, delivery, and consumption. Unlike the traditional power grid, a smart grid involves significant data communication across the grid. However, in the current practice, different areas of the power domain use different data semantic models, which has caused significant interoperability issues among systems and become a major barrier toward smart grids. Interoperability issues can also arise in communication. There has been growing interest in adopting publish-subscribe communication for improved quality of communication in smart grids. However, adopting publish-subscribe communication requires resolving potential interoperability issues with the client-server communication in the traditional power grid. In this article, we explore interoperability issues in smart grids and discuss how they can be addressed from the data and communication perspectives. [ABSTRACT FROM PUBLISHER]

In mobile social networks, mobile users may help each other transfer contents when they move and meet each other. In this paper, we consider a mobile publish–subscribe network in which a mobile user (i.e., a content source) incentivizes other users (i.e., messengers) to forward its content by transferring energy to them. The messengers can utilize the received energy for content forwarding and/or their own use. From the perspective of a rational content source, to optimize the content delivery performance, we formulate the problem of energy charging and content transferring as a Markov decision process (MDP): a framework for decision-making in stochastic systems. The objective is to maximize the expected utility in terms of the benefit gained by the content source from delivering the content and cost from energy consumption and transfer. The solution to the MDP is proved to be a threshold policy. Performances of the MDP-based scheme are examined in different system scenarios. The numerical results show that the MDP-based scheme outperforms the conventional baseline schemes. [ABSTRACT FROM PUBLISHER]

This paper presents a decentralized Web-based architecture designed to support the development of distributed, dynamic, context-aware and interoperable services and applications. The architecture enables the detection and notification of changes over the Web of Data by means of a content-based publish-subscribe mechanism where the W3C SPARQL 1.1 Update and Query languages are fully supported and used respectively by publishers and subscribers. The architecture is built on top of the W3C SPARQL 1.1 Protocol and introduces the SPARQL 1.1 Secure Event protocol and the SPARQL 1.1 Subscribe Language as a means for conveying and expressing subscription requests and notifications. The reference implementation of the architecture offers to developers a design pattern for a modular, scalable and effective application development.

Middlewares are standard tools for modern software development in many areas, especially in robotics. Although such have become common for high-level applications, there is little support for real-time systems and low-level control. Therefore, µRT provides a lightweight solution for resource-constrained embedded systems, such as microcontrollers. It features publish-subscribe communication and remote procedure calls (RPCs) and can validate timing constraints at runtime. In contrast to other middlewares, µRT does not rely on specific transports for communication but can be used with any technology. Empirical results prove the small memory footprint, consistent temporal behavior, and predominantly linear scaling. The usability of µRT was found to be competitive with state-of-the-art solutions by means of a study., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Schöpping, Kenneweg, Hesse and Rückert.)

Many future vehicular ad hoc network (VANET) applications will be event driven and will require events of different types to be delivered to moving vehicles within some specified time. In this paper, we propose a publish–subscribe based event notification framework that uses roadside units (RSUs) to deliver events to vehicles that subscribe to them within the validity periods of both the subscriptions and the events. Each RSU can disseminate only a finite number of events at a time and has a cost associated with it. Two scheduling problems to schedule the dissemination of events from RSUs are formulated. The first problem aims to maximize only the number of subscriptions that are matched to some events. The second problem, in addition to maximizing the number of subscriptions matched, also aims to minimize the total cost of disseminating the events. We have designed offline and online algorithms for the problems that a service provider can execute to schedule event disseminations from the RSUs. Detailed simulation results are presented to show that the algorithms are able to match a high percentage of subscriptions with low average event dissemination cost for some realistic city traffic scenarios. [ABSTRACT FROM PUBLISHER]

This paper explores advantages that a publish/subscribe middleware can offer for the implementation of an efficient and reliable electric vehicle (EV) charging control infrastructure. We propose distributed optimization publish and subscribe (DOPS), a framework for distributed optimization of EV charging, which works on top of a pub/sub middleware and extends it to support in-network aggregation. For our evaluation, we deployed DOPS in a testbed consisting of 15 virtual machines connected via a VLAN network and compared three different communication schemes: centralized, decentralized and decentralized with aggregation. Our results show that for up to 120 EVs a centralized approach is faster. However, the trends reveal that for more than 150 EVs a decentralized approaches will offer better performance. Moreover, we demonstrate that the in-network aggregation feature of DOPS doubles the performance of the decentralized approach. Our results thus confirm that distributed control infrastructures can benefit from using pub/sub middleware. [ABSTRACT FROM AUTHOR]

This letter describes the architecture of an inter-domain message passing hardware sub-system targeting the embedded virtualization field. Embedded virtualization is characterized by application-specific solutions, where functionality is partitioned into a small, fixed number of Virtual Machines, typically under real-time constraints, which must communicate for synchronization and status signaling. In light of the growing use of custom hardware, especially supported by (re)configurable platforms, we show how our hardware sub-system can provide virtualization-safe data transfers, without the need for Hypervisor (software) mediation, through the use of translate-once and virtual-interface hardware mechanisms, allowing direct memory-to-memory copies between different partitions’ input/output buffers, in both direct-transfer and publish-subscribe modes. Our experiments show our architecture is especially suited for the real time domain, outperforming an equivalent software solution in latencies, throughput and jitter, and outperforming state of the art hardware solutions for small message sizes (<512 B). [ABSTRACT FROM PUBLISHER]

SAMP, the Simple Application Messaging Protocol, is a hub-based communication standard for the exchange of data and control between participating client applications. It has been developed within the context of the Virtual Observatory with the aim of enabling specialised data analysis tools to cooperate as a loosely integrated suite, and is now in use by many and varied desktop and web-based applications dealing with astronomical data. This paper reviews the requirements and design principles that led to SAMP’s specification, provides a high-level description of the protocol, and discusses some of its common and possible future usage patterns, with particular attention to those factors that have aided its success in practice. [ABSTRACT FROM AUTHOR]

Event-driven programming in large scale environments is becoming a common requirement of modern distributed applications. It introduces some beneficial effects such as real-time state updates and replications, which enable new kinds of applications and efficient architectural solutions. However, these benefits could be compromised if the adopted infrastructure were not designed to ensure efficient delivery of events and related data. This paper presents an architectural model, a middleware (WS-Link) and annotation-based mechanisms to ensure high performance in delivering events carrying large attachments. We transparently decouple event notification from related data to avoid useless data-transfers. This way, while event notifications are routed in a conventional manner through an event service, data are directly and transparently transferred from publishers to subscribers. The theoretical analysis shows that we can reduce the average event delivery time by half, compared to a conventional approach requiring the full mediation of the event service. The experimental analysis confirms that the proposed approach outperforms the conventional one (both for throughput and delivery time) even though the middleware overhead, introduced by the specific adopted model, slightly reduces the expected benefits. [ABSTRACT FROM AUTHOR]

Applications such as Facebook, Twitter and Foursquare have brought the mass adoption of personal short messages, distributed in (soft) real-time on the Internet to a large number of users. These messages are complemented with rich contextual information such as the identity, time and location of the person sending the message (e.g., Foursquare has millions of users sharing their location on a regular basis, with almost 1 million updates per day). Such contextual messages raise serious concerns in terms of scalability and delivery delay; this results not only from their huge number but also because the set of user recipients changes for each message (as their interests continuously change), preventing the use of well-known solutions such as pub-sub and multicast trees. This leads to the use of non-scalable broadcast based solutions or point-to-point messaging. We propose Radiator, a middleware to assist application programmers implementing efficient context propagation mechanisms within their applications. Based on each user's current context, Radiator continuously adapts each message propagation path and delivery delay, making an efficient use of network bandwidth, arguably the biggest bottleneck in the deployment of large-scale context propagation systems. Our experimental results demonstrate a 20x reduction on consumed bandwidth without affecting the real-time usefulness of the propagated messages. [ABSTRACT FROM AUTHOR]