Synchronous Communication Mechanism Research Articles

E-MQTT: End-to-End Synchronous and Asynchronous Communication Mechanisms in MQTT Protocol

Message Queuing Telemetry Transport (MQTT) enables asynchronous confirmation of message reception by brokers but lacks a way for publishers to know when subscribers receive their messages without adding additional communication overhead. This paper addresses this problem by improving MQTT to establish end-to-end communication between a publisher and subscribers, reducing message exchanges, using what is called End-to-End MQTT (E-MQTT). In E-MQTT, a publisher sets the number of responses that it will wait for when it sends a message. After the broker collects the response messages from subscribers, it sends one aggregated response back to the publisher. The publisher also can receive the response message synchronously or asynchronously. Experimental results consistently show that E-MQTT outperforms traditional MQTT in terms of delay, especially when the publisher needs to monitor when its query message is received by subscribers. Although E-MQTT packets are slightly larger due to additional fields, the difference in packet size compared to MQTT is not significant.

Event-Based Microservices With Apache Kafka Streams: A Real-Time Vehicle Detection System Based on Type, Color, and Speed Attributes

The work presented in this paper proposes a novel approach to tracking a specific vehicle over the video streams published by the collaborating traffic surveillance cameras. In recent years, smart, effective transportation systems and intelligent traffic management applications are among the topics that have been given importance by various institutions. Developing a scalable, fault-tolerant, and resilient traffic monitoring system that retrieves video chunks with the desired query is challenging. For these challenging problems, stream processing and data retrieval systems have been developed over the years. However, there are still existing shortcomings between users and retrieval systems. This paper investigates the problem of retrieving video chunks by key-value query based on publish/subscribe model. Thus, we propose a hybrid of an asynchronous and synchronous communication mechanism for the Event-Based Microservice framework. We aim to develop generic techniques for better utilization of existing platforms. In the proposed framework, (i) first of all, microservices detect vehicles and extract their type, color, and speed features, and stored them in the metadata repository. (ii) Microservices publish each feature as events (iii) Other microservices self-join subscribe to those events, which leads to more events being published by combing all the possibilities: type-color, type-speed, color-speed, and type-color-speed. Finally, (iv) the system visualizes the query result and system status in real-time. When the user has selected color or/and a type or/and a speed feature, the system will return the best-matched vehicles without re-processing the videos. Experimental results show that our proposed system filters messages in real-time and supports easy integration of new microservices with the existing system.

Directly and Indirectly Synchronous Communication Mechanisms for Client-Server Systems Using Event-Based Asynchronous Communication Framework

In this paper, we propose a synchronous communication mechanism that can be used with asynchronous communication in an event-based communication framework (CM). The proposed synchronous communication mechanism supports directly synchronous communication between client and server, indirectly synchronous communication between two clients through server mediation, and indirectly one-to-many synchronous communication with multiple clients. In order to support synchronous communication, the CM uses the synchronization mechanism between the main thread and the processing thread while maintaining the multi-thread structure. The application can utilize both the asynchronous and the synchronous communication service of the CM together according to its requirements. For performance analysis, we compared the CM synchronous and asynchronous communication methods with qualitative and quantitative experiments, respectively. Through qualitative analysis, developing applications using synchronous services can more intuitively design application logic than asynchronous services. From the quantitative experiment, we also verified that the response delay time in the synchronous method is shorter than that in the asynchronous method although the difference in the response delay is not large.

Bio-inspired self-aware fault-tolerant routing protocol for network-on-chip architectures using Particle Swarm Optimization

This research paper proposes a bio-inspired self-aware fault-tolerant routing protocol for network-on-chip architecture using particle swarm optimization (PSO), which considers synchronous, asynchronous, and self-organizing communication mechanisms to intelligently load-balance the traffic on the entire network in the presence of faulty components. By way of experimentation and simulation, this study demonstrates that the proposed scheme can converge to a global optimum, minimal routing path in real time, in the presence of network congestion and faulty routers and links. The basic PSO algorithm was improved to implement the proposed routing scheme, named bio-inspired self-aware fault-tolerant routing protocol (BISFTRP). This scheme uses the synchronous, asynchronous, and self-organizing features of PSO to create a global routing table and intelligent adaptation, which gives rise to scalable, real-time, and dynamic routing decisions with high throughput, low latency, and minimum power consumption. A cycle-accurate simulation system to demonstrate the flexibility and efficiency of the proposed scheme is used. Comparison results with state-of-the-art fault-tolerant routing algorithms show that the BISFTRP routing protocol achieves high routing performance without routing oscillations and throughput degradation. Furthermore, the hardware implementation results show that the BISFTRP router achieves an efficient area and power utilization, compared with state-of-the-art routers.

Design and implementation of inter-domain communication mechanism for high performance data processing

The basic improvement in the computer operation is the involvement of multi-operating systems running on a physical computer. To make extensive use of virtualization technologies in cloud computing, the inter-domain communication effectiveness is a key factor for the functioning of distributed applications and some intensive network applications. The synchronous communication mechanism, used by the traditional virtual machine implementation mechanism based on the asynchronous signal fed by the virtual machine mechanism, often causes high latency and slow performance. The communication mechanism, called com-socket that uses interprocessor interrupts for synchronization and elimination of some unnecessary packet inspections is developed and implemented. The approach of using shared memory to reduce the data copying time is applied. The com-socket implementation is carried out on X86 in combination with the virtual machine mechanism. The study revealed that the com-socket has lower latency and higher performance compared to UNIX IPC.

An Online Interactive Competition Model for E-Learning System

This paper presents an Online Interactive Competition Model for E-learning System. The system allows a student to connect and interact with other students on the courses they offer in a semester using both synchronous and asynchronous computer-mediated communication mechanisms. Each course lecturer e-supervises and e-moderates the students’ performances in his/her course. Following the semester course outlines, the system automatically and periodically selects topics for discussions. Each student’s questions as well as his/her contributions to questions posed by other students or even the lecturers on the e-learning platform are rated by the course lecturers who equally make their contributions in difficult cases. On registration, a student is assigned the rank of a starter in all courses. Based on a course lecturer’s ratings on a student and how long the student had used the course page, the student may rise to the following ranks in the course: Senior, Master, Expert or Professional. In this paper, the scalable algorithm for the students’ ranking is presented. Moreover, a student’s ranks in different courses are independent; that is, a student can be an expert in one course and a starter in another. This ranking strategy serves as an incentive to encourage the students to participate actively and make meaningful contributions to questions posted on the platform. A working prototype of the system was developed using MySQL Database Management System (DBMS), PHP as the scripting language and Apache as the web server. The system was tested and the results were presented graphically in this paper. http://dx.doi.org/10.4314/njt.v34i3.18

Rapyuta: A Cloud Robotics Platform

In this paper, we present the design and implementation of Rapyuta, an open-source cloud robotics platform. Rapyuta helps robots to offload heavy computation by providing secured customizable computing environments in the cloud. The computing environments also allow the robots to easily access the RoboEarth knowledge repository. Furthermore, these computing environments are tightly interconnected, paving the way for deployment of robotic teams. We also describe three typical use cases, some benchmarking and performance results, and two proof-of-concept demonstrations. Note to Practitioners - Rapyuta allows to outsource some or all of a robot's onboard computational processes to a commercial data center. Its main difference to other, similar frameworks like the Google App Engine is that it is specifically tailored towards multiprocess high-bandwidth robotics applications/middlewares and provides a well-documented open-source implementation that can be modified to cover a large variety of robotic scenarios. Rapyuta supports the outsourcing of almost all of the current 3000+ ROS packages out of the box and is easily extensible to other robotic middleware. A pre-installed Amazon Machine Image (AMI) is provided that allows to launch Rapyuta in any of Amazon's data center within minutes. Once launched, robots can authenticate themselves to Rapyuta, create one or more secured computational environments in the cloud and launch the desired nodes/processes. The computing environments can also be arbitrarily connected to build parallel computing architectures on the fly. The WebSocket-based communication protocol, which provides synchronous and asynchronous communication mechanisms, allows not only ROS based robots, but also browsers and mobiles phones to connect to the ecosystem. Rapyuta's computing environments are private, secure, and optimized for data throughput. However, its performance is in large part determined by the latency and quality of the network connection and the performance of the data center. Optimizing performance under these constraints is typically highly application-specific. The paper illustrates an example of performance optimization in a collaborative real-time 3-D mapping application. Other target applications include collaborative 3-D mapping, task/grasp planning, object recognition, localization, and teleoperation, among others.

Asynchronous Communication Mechanism Oriented Wireless Sensor Networks and MAC Protocols

Underlying communication of wireless sensor networks is mainly depending on coordinated sleep/wakeup mechanisms,and is still basing the link layer protocols upon the traditional 802.11.For wireless sensor networks usually having high node density and large scale,802.11 protocol is prone to be not efficient in energy consumption,network throughput etc.Basing on the dynamic links in a large portion of monitoring applications of wireless sensor networks,this paper proposes a kind of weak connection-oriented asynchronous communication mechanism (ACM).Differential from traditional RTS/CTS handshaking mechanism,ACM allows transmitter directly write the data into the low power asynchronous module on receiver while it is sleep. In this way,each node can schedule its own transmission without demanding network synchronization. The result is a store-wakeup-forward,asynchronous communication mode in the network. This paper describes the key factors of ACM and proposes two kinds of MAC protocols for differ- ent applications.Moreover,the diffusion approximation based open queuing model is established to analyze the performance of ACM,proving the throughput of ACM is O(W/(n/logn) ^0.5). Analytical and experimental results show that,compared to synchronous communication mechanism, ACM is able to prolong network lifetime and improve the throughput.

ISIPC: Instant Synchronous Interprocess Communication

Interprocess communication (IPC) is often used to exchange data between cooperative processes, and the performance of IPC largely determines the processing time of application programs. Moreover, it is used for most of the kernel calls in a microkernel-based operating system (OS). Therefore, the performance of IPC affects the performance of the OS. In addition, the completion of the messagepassing mechanism has to be indicated by executing a receive operation in order to maintain synchronization. Thus, two operations are required in this mechanism to complete the communication. On the other hand, no receive operation is required to indicate the completion of the communication in the case of asynchronous communication; however, in this case, no proof of the data being received is provided to the sender process. In this paper, we propose an instant synchronous interprocess communication (ISIPC) mechanism that can achieve both instantaneous communication and data synchronization. ISIPC has two functions: push function and sack function. We describe the design of the ISIPC mechanism and also its implementation on the Tender operating system. In addition, we present the evaluation results for the ISIPC mechanism.

Framed temporal logic programming

A Projection Temporal Logic is discussed and some of its laws are given. After that, an executable temporal logic programming language, called Framed Tempura, is formalized. A minimal model-based approach for framing in temporal logic programming is presented. Since framing destroys monotonicity, canonical models–used to define the semantics of non-framed programs–are no longer appropriate. To deal with this, a minimal model theory is developed, using which the temporal semantics of framed programs is captured. The existence of a minimal model for a given framed program is demonstrated. A synchronous communication mechanism for concurrent programs is provided by means of the framing technique and minimal model semantics.

Conceptual design of remote monitoring and fault diagnosis systems

Condition monitoring and fault diagnosis are of fundamental importance for many industrial systems. In the last decade, substantial research efforts have been made on the surveillance and diagnosis systems for different types of equipment, with the approach of integrating information technologies and intelligent computing methods. This paper presents the conceptual design of a distributed information system of condition monitoring and fault diagnosis for a growing number of gas turbine-based power generation systems. Each individual information system that monitors a specific gas turbine system, locally deployed in a power plant, is linked to another information system, deployed at the manufacturer's site, which oversees all the gas turbine systems in parallel. The systems are constructed on the basis of COM components, which are conceptually separated into three tiers. Subsequently, this paper proceeds to present a generic business domain model with components encapsulating physical entities of interest. Finally, this paper addresses the interactions among components, which considerably affect the performance of the system including efficiency and effectiveness. It has been identified that both asynchronous and synchronous communication mechanisms are required for exchanging information for different scenarios. COM+ services are also required for supporting object pooling, transaction coordination, and security control.

A compile-time optimization framework for Ada rendezvous

Rendezvous is the basic synchronous communication mechanism used by tasks, which causes tasks blocked under some circumstances. Holding the semantics of the rendezvous, this paper uses semaphores to transform the entry call and accept statement pairs and makes tasks execute some statements during the blocked time because of waiting for the beginning or end of a rendezvous. Therefore, the parallelism between the client and the server is improved.

A fully abstract model for the exchange of information in multi-agent systems

In this paper,11This paper is an extended version of [7]. we present a semantic theory for the exchange of information in multi-agent systems. We consider the multi-agent programming language agent communication programming language, which integrates the paradigms of concurrent constraint programming and communicating sequential processes (CSP). The constraint programming techniques are used to represent and process information, whereas the synchronous communication mechanism from CSP is generalised to enable the exchange of information. The semantics of the language, which is based on a generalisation of traditional failure semantics, is shown to be fully abstract with respect to observing of each terminating computation its final global store of information.

A collision problem in OSI standard formal specifications

Abstract A collision problem is presented which can occur between two adjacent protocol entities, a user and its local provider. We consider synchronous and asynchronous communication mechanisms at the Service Access Point between the entities; this is normally an implementation choice. It is shown that even if the problem is limited by using a synchronous communication mechanism, instead of an asynchronous one, it still occurs. We suggest that whenever this case is found, the service provided by the protocol entity must be interpreted differently by its user, ignoring some primitives. When an asynchronous communication mechanism is used, care must be taken to verify that those primitives to be ignored cannot be misinterpreted as new primitives; finally, we point out that the protocol specification could be redesigned to handle these collision cases properly.

Synchronous and asynchronous handling of abnormal events in the μsystem

AbstractThis paper presents a general model for dealing with abnormal events during program execution and describes how this model is implemented in the μSystem. (The μSystem is a library of C definitions that provide light‐weight concurrency on uniprocessor and multiprocessor computers running the UNIX operating system.) Two different techniques can be used to deal with an abnormal event: an exception, which results in an exceptional change in control flow from the point of the abnormal event; and an intervention, which is a routine call from the point of the abnormal event that performs some corrective action. Users can define named exceptions and interventions in conjunction with ones defined by the μSystem. Exception handlers and intervention routines for dealing with abnormal events can be defined/installed at any point in a program. An exception or intervention can then be raised or called, passing data about the abnormal event and returning results for interventions. Interventions can also be activated in other tasks, like a UNIX signal. Such asynchronous interventions may interrupt a task's execution and invoke the specified intervention routine. Asynchronous interventions are found to be useful to get another task's attention when it is not listening through the synchronous communication mechanism.

A synchronous approach for clocking VLSI systems

Presents a synchronous solution for clocking VLSI systems organized as distributed systems. This solution avoids the drawbacks of the self-timed approach. These VLSI systems are constituted of modules which represent synchronous areas driven by their own fast clock, interconnected by a synchronous communication mechanism driven by a slow clock. In order to avoid the risk of metastability in flip-flop between the modules and the communication mechanism, the author suggests to resynchronize the phase of each module clock on the transitions of the communication clock by a phase locked loop circuitry added to each module.