Coordination Messages Research Articles

A Biologically Inspired Self-Organizing Underwater Sensor Network

Wireless underwater sensor networks have various applications—such as ocean exploration and deep-sea disaster monitoring—making them a hot topic in the research field. To cover a larger area and gather more-precise information, building large-scale underwater sensor networks has become a trend. In such networks, acoustic signals are used to transmit messages in an underwater environment. Their features of low speed and narrow bandwidth make media access control (MAC) protocols unsuitable for radio communications. Furthermore, a network consists of a large number of randomly deployed nodes, making it impossible to pre-define an optimized routing table or assign a central controller to coordinate the message propagation process. Thus, optimized routing should emerge via interaction among individual nodes in the network. To address these challenges, in this paper we propose a communication coordinator under the time division multiple access (TDMA) framework. Each node in the network is equipped with such a coordinator so that messages in the network can be sent following the shortest path in a self-organized way. The coordinator consists of a slot distributor and a forwarding guide. With the slot distributor, nodes in the sensor network occupy proper communication slots and the network finally converges to the state without communication collision. This is achieved with a set of ecological niche- and pheromone-inspired laws, which encourage nodes to occupy slots that can decrease the waiting time for a node to send a message packet while weakening the enthusiasm for a node to occupy the slots that it fails to occupy several times. With the forwarding guide, a node can send the message packet to the best successor node so that the message packet can be sent to the base station along the shortest path. It has been proven that the laws in the forwarding guide are equivalent to the Dijkstra Algorithm. Simulation experiment results indicate that with our coordinator, the network can converge to the state without collision using fewer coordination messages. In addition, the time needed to send a message to the destination is shorter than that of the classical Aloha protocol.

The Quantum Internet: Enhancing Classical Internet Services One Qubit at A Time

Nowadays, the classical Internet is mainly envisioned as the underlying communication infrastructure of the Quantum Internet, aimed at providing services such as signaling and coordination messages. However, the interplay between the classical and the quantum Internet is complex and its understanding is pivotal for an effective design of the Quantum Internet protocol stack. The aim of the article is to shed light on this interplay, by highlighting the fact that such an interplay is indeed bidirectional rather than unidirectional. The Quantum Internet exhibits the potential of supporting and even enhancing classical Internet functionalities.

Agent-based distributed protocol for resource discovery and allocation of virtual networks over elastic optical networks

Network virtualization is a key enabling technology for “Infrastructure as a Service” provisioning, increasing the flexibility and cost savings offered to customers. By extending the concept of server virtualization to the network infrastructure, the allocation of different, independent virtual networks over a single physical network is carried out on demand. A fundamental challenge in network virtualization systems is to choose which physical nodes and links to use for hosting virtual networks in the physical infrastructure, known as the “virtual network allocation” problem. All virtual network allocation proposals on elastic optical networks assume a centralized operation, deploying a single node with access to the network state global information and assigning resources accordingly. However, such configuration might exhibit the inherent problems of centralized systems: survivability and scalability. In this paper, we present a distributed protocol for resource discovery, mapping, and allocation of network virtualization systems. The distributed protocol is generic enough as to be used with different substrate networks. However, in this paper, it has been adapted to work over an elastic optical network infrastructure, where further considerations regarding the spectrum continuity and contiguity constraints must also be taken into account. The distributed protocol is based on the concept of alliances: upon the arrival of a virtual network request, agents located in the physical network nodes compete to form the first alliance able to host the virtual network. Because the first alliances to be formed are also the ones composed by nearby nodes, a good network resource usage is achieved. The feasibility of the distributed protocol was studied by evaluating its ability to successfully establish virtual networks within acceptable time and with low bandwidth consumption from the coordination messages.

SwitchTx

Online-transaction-processing (OLTP) applications require the underlying storage system to guarantee consistency and serializability for distributed transactions involving large numbers of servers, which tends to introduce high coordination cost and cause low system performance. In-network coordination is a promising approach to alleviate this problem, which leverages programmable switches to move a piece of coordination functionality into the network. This paper presents a fast and scalable transaction processing system called SwitchTx. At the core of SwitchTx is a decentralized multi-switch in-network coordination mechanism, which leverages modern switches' programmability to reduce coordination cost while avoiding the central-switch-caused problems in the state-of-the-art Eris transaction processing system. SwitchTx abstracts various coordination tasks (e.g., locking, validating, and replicating) as in-switch gather-and-scatter (GaS) operations, and offloads coordination to a tree of switches for each transaction (instead of to a central switch for all transactions) where the client and the participants connect to the leaves. Moreover, to control the transaction traffic intelligently, SwitchTx reorders the coordination messages according to their semantics and redesigns the congestion control combined with admission control. Evaluation shows that SwitchTx outperforms current transaction processing systems in various workloads by up to 2.16X in throughput, 40.4% in latency, and 41.5% in lock time.

Communizer: A collaborative cloud-based self-protecting software communities framework - Focus on the alert coordination system

Popular software has always been appealing to adversaries, as related vulnerabilities are synonymous with millions of exposed businesses. Collaborative intrusion detection, as well as software self-protection, try to alleviate this situation. However, they lack either autonomy and adaptation, or Internet-scale oversight and mitigation. In this work, we present Communizer: a collaborative cloud-based framework that creates communities of self-protecting software across organizations. It allows community members to turn their common weaknesses into collaborative and proactive self-protection, empowering them to detect intrusions, exchange alerts, and anticipate attacks. We start by integrating multiple autonomic MAPE-K loops through cloud-based coordination, and a novel hierarchical, regional coordination pattern (HRCP), optimizing scalability, resiliency, accuracy and privacy. Then, we design a trust-based multi-level alert coordination system (TMACS), as well as a lightweight alert coordination message exchange format (ACMEF). At its core, TMACS aggregates, validates, and shares security alerts among community members while fostering agreement and managing trust. It also addresses insider attacks by detecting and blacklisting rogue members. Moreover, TMACS identifies and neutralizes selfish members through a specifically designed probabilistic model. The analysis, optimization, and evaluation of TMACS show a good trade-off between the precision and recall of untrustworthy and selfish members detection. More importantly, we demonstrate a drastic reduction of monitoring loads on community members while ensuring a high collaborative attack detection and anticipation rate, even for small-scope attacks.

NR Sidelink Enhancement in 3GPP Release 17

3GPP is currently studying enhancements to Sidelink (SL) operations for 5G New Radio (NR) in a Release 17 Work Item which is planned to be finished by end of 2021. The NR Sidelink (SL) Work Item in Release 17 includes several key features targeting reliability enhancements, power saving and coverage enhancements by expanding the scope of NR sidelink to target V2X, commercial D2D use-case and Public safety. This paper provides an insight on the current 3GPP Release 17 NR SL design describing necessary enhancements in the physical, protocol layer to support inter-UE coordination message for reliability enhancement for autonomous resource selection procedure by providing feedback on the half-duplex, persistent collision and hidden nodes. In addition, the power saving feature is addressed by introducing a SL DRX mechanism for the PC5 interface which defines active reception and transmission periods between a TX and the peer Rx UE(s) and also between Tx UE and gNB. Furthermore, this paper outlines details on the Sidelink Relay feature for coverage enhancement by describing possible solutions for UE to Network relay and UE to UE relay.

Stability and Convergence of a Message-Loss-Tolerant Rendezvous Algorithm for Wireless Networked Robot Systems

This article considers the problem of swarm rendezvous when robots exchange local coordination messages through an unreliable wireless communication network (i.e., message-loss occurs). First, a discrete-time second-order consensus algorithm is provided to deal with the effects of unreliable channels on wireless networked robot (WNR) systems, and drive the robots to a given geometric formation. Then, necessary and sufficient conditions for the controlled WNR to converge to a desired formation, even in the presence of messages loss, are formulated and simulatively validated. The proposed conditions provide to the WNR designer a minimal topology connectivity requirement, and a relation among algorithm step-size and control gains to be fulfilled for guaranteeing swarm rendezvous.

Local Observability and Controllability Analysis and Enforcement in Distributed Testing With Time Constraints

Evermore end-to-end digital services depend on the proper interoperation of multiple products, forming a distributed system, often subject to timing requirements. To ensure interoperability and the timely behavior of such systems, it is important to conduct integration tests that verify the interactions with the environment and between the system components in key scenarios. The automation of such integration tests requires that test components are also distributed, with local testers deployed close to the system components, coordinated by a central tester. Test coordination in such a test architecture is a big challenge. To address it, in this article we propose an approach based on the pre-processing of the test scenarios. We first analyze the test scenarios in order to check if conformance errors can be detected locally (local observability) and test inputs can be decided locally (local controllability) by the local testers for the test scenario under consideration, without the need for exchanging coordination messages between the test components during test execution. If such properties do not hold, we next try to determine a minimum set of coordination messages or time constraints to be attached to the given test scenario to enforce those properties and effectively solve the test coordination problem with minimal overhead. The analysis and enforcement procedures were implemented in the DCO Analyzer tool for test scenarios described by means of UML sequence diagrams. Since many local observability and controllability problems may be caused by design flaws or incomplete specifications, and multiple ways may exist to enforce local observability and controllability, the tool was designed as a static analysis assistant to be used before test execution. DCO Analyzer was able to correctly identify local observability and controllability problems in real-world scenarios and help the users fix the detected problems.

Bubbles and crashes: A laboratory experiment

Most lab experiments carried out on asset price bubbles have been based upon theoretical models that do not factor in a bubbling equilibrium. The aim of this paper is to propose a lab experiment which uses a model with bubbling equilibrium as its benchmark; to specify we used a modified version of the model built by Abreu and Brunnermeier (2003). In both models the asymmetries of information regarding the existence of the asset price bubbles induce rational traders to perpetuate the bubbles. In our experiment we found that human traders are, most of the time, risk averse, they suffer impatience and do not necessarily react appropriately to coordination messages (even though the presence of said messages affects their behavior) and sometimes they clearly behave irrationally. Last but not least, during the experiment we also found that the human traders could adapt their strategies to optimal equilibrium strategies, so long as these strategies were not too complex - but not all human traders have the same ability to execute this adaptation process.

Does team competition increase pro-social lending? Evidence from online microfinance

We investigate the effects of team competition on pro-social lending activity on Kiva.org, the first microlending website to match lenders with entrepreneurs in developing countries. Using naturally occurring field data, we find that lenders who join teams contribute 1.2 more loans ($30–$42) per month than those who do not. To further explore factors that differentiate successful teams from dormant ones, we run a large-scale randomized field experiment (n=22,233) by posting forum messages. Compared to the control, we find that lenders make significantly more loans when exposed to a goal-setting and coordination message, whereas goal-setting alone significantly increases lending activities of previously inactive teams. Our findings suggest that goal-setting and coordination are effective mechanisms to increase pro-social behavior in teams.

On Deferred Constraints in Distributed Database Systems

An atomic commit protocol (ACP) is a distributed algorithm used to ensure the atomicity property of transactions in distributed database systems. Although ACPs are designed to guarantee atomicity, they add a significant extra cost to each transaction execution time. This added cost is due to the overhead of the required coordination messages and log writes at each involved database site to achieve atomicity. For this reason, the continuing research efforts led to a number of optimizations that reduce the aforementioned cost. The most commonly adopted optimizations in the database standards and commercial database management systems are those designed around the early release of read locks of transactions. In this type of optimizations, certain participating sites may start releasing the read locks held by transactions before they are fully terminated across all participants. Hence, greatly enhancing concurrency among executing transactions and, consequently, the overall system performance. However, this type of optimizations introduces possible “execution infections” in the presence of deferred consistency constraints; a devastating complication that may lead to non-serializable executions of transactions. Thus, this type of optimizations could be considered useless, given the importance of preserving the consistency of the database in presence of deferred constraints, unless this complication is resolved in a practical and efficient manner. This is the essence of the “unsolicited deferred consistency constraints validation” mechanism presented in this paper.

Group planning with time constraints

Embedding planning systems in real-world domains has led to the necessity of Distributed Continual Planning (DCP) systems where planning activities are distributed across multiple agents and plan generation may occur concurrently with plan execution. A key challenge in DCP systems is how to coordinate activities for a group of planning agents. This problem is compounded when these agents are situated in a real-world dynamic domain where the agents often encounter differing, incomplete, and possibly inconsistent views of their environment. To date, DCP systems have only focused on cases where agents’ behavior is designed to optimize a global plan. In contrast, this paper presents a temporal reasoning mechanism for self-interested planning agents. To do so, we model agents’ behavior based on the Belief-Desire-Intention (BDI) theoretical model of cooperation, while modeling dynamic joint plans with group time constraints through creating hierarchical abstraction plans integrated with temporal constraints network. The contribution of this paper is threefold: (i) the BDI model specifies a behavior for self interested agents working in a group, permitting an individual agent to schedule its activities in an autonomous fashion, while taking into consideration temporal constraints of its group members; (ii) abstract plans allow the group to plan a joint action without explicitly describing all possible states in advance, making it possible to reduce the number of states which need to be considered in a BDI-based approach; and (iii) a temporal constraints network enables each agent to reason by itself about the best time for scheduling activities, making it possible to reduce coordination messages among a group. The mechanism ensures temporal consistency of a cooperative plan, enables the interleaving of planning and execution at both individual and group levels. We report on how the mechanism was implemented within a commercial training and simulation application, and present empirical evidence of its effectiveness in real-life scenarios and in reducing communication to coordinate group members’ activities.

Overcoming controllability problems in distributed testing from an input output transition system

This paper concerns the testing of a system with physically distributed interfaces, called ports, at which it interacts with its environment. We place a tester at each port and the tester at port p observes events at p only. This can lead to controllability problems, where the observations made by the tester at a port p are not sufficient for it to be able to know when to send an input. It is known that there are test objectives, such as executing a particular transition, that cannot be achieved if we restrict attention to test cases that have no controllability problems. This has led to interest in schemes where the testers at the individual ports send coordination messages to one another through an external communications network in order to overcome controllability problems. However, such approaches have largely been studied in the context of testing from a deterministic finite state machine. This paper investigates the use of coordination messages to overcome controllability problems when testing from an input output transition system and gives an algorithm for introducing sufficient messages. It also proves that the problem of minimising the number of coordination messages used is NP-hard.

A New Co-Ordinated Checkpointing and Rollback Recovery Scheme for Distributed Shared Memory Clusters

In this paper, an unified lightweight error recovery scheme based on coordinated checkpointing and rollback for distributed shared memory clusters is proposed. The new scheme maintains multiple globally consistent checkpoints of the state of a distributed shared memory cluster and recovers to a pre-fault checkpoint of the system. It also describes and evaluates the coordinated checkpointing. The coordinated checkpoint neither needs to exchange coordination messages nor adds information to the process messages. It only accesses stable storage when checkpoints are saved. Each of the processes saves its state independently from the other processes. The checkpoint timers are set at different processes. Based on the results of performance evaluation the proposed scheme is shown to outperform the previously proposed checkpoint and recovery schemes for distributed shared memory clusters .

Optimal Cooperative Relaying Schemes in IR-UWB Networks

Cooperation between wireless nodes to retransmit data for the other users introduces multiuser diversity to a wireless network and increases the system throughput. In this paper, the optimal cooperative relaying strategies in the MAC layer are analyzed while considering the UWB unique properties such as fine ranging and immunity to small scale fading. Specifically, the optimal cooperation strategies in the absence of coordination message passing between relays are determined in order to maximize the system throughput while reducing the control packet overhead. Mobile networks are also considered, in which the relays should exchange their ranging information together in some update intervals. The optimal update interval length is calculated in order to maximize the system throughput. More importantly, we show that if this optimal update interval is used, the optimal cooperation strategies in the mobile case will be similar to those in the static network. Two different relay selection schemes, namely proactive and reactive settings, are considered. Analysis and simulations confirm that the proposed UWB-based Cooperative Relaying Scheme, UCoRS, can achieve a considerable diversity gain in spite of its implementation simplicity. UCoRS also minimizes the number of control packets that are required for the optimal cooperation, which leads to the energy efficiency in the UWB costly data-receiving process.

Overcoming controllability problems with fewest channels between testers

When testing a system that has multiple physically distributed ports/interfaces it is normal to place a tester at each port. Each tester observes only the events at its port and it is known that this can lead to additional controllability problems. While such controllability problems can be overcome by the exchange of external coordination messages between the testers, this requires the deployment of an external network and may thus increase the costs of testing. The problem studied in this paper is finding a minimum number of coordination channels to overcome controllability problems in distributed testing. Three instances of this problem are considered. The first problem is to find a minimum number of channels between testers in order to overcome the controllability problems in a given test sequence to be applied in testing. The second problem is finding a minimal set of channels that allow us to overcome controllability problems in any test sequence that may be selected from the specification of the system under test. The last problem is to find a test sequence that achieves a particular test objective and in doing so allows fewest channels to be used.

Multiple UIO-based test sequence generation for distributed systems

In developing distributed systems, conformance testing is required to determine whether an implementation under test (IUT) conforms to its specification. With distributed test architectures involving multiple remote testers, testing approaches may become more complicated because of issues known as controllability and observability problems. Based on a finite state machine (FSM) representation of the system’s specification, this paper proposes a new method to generate a test sequence utilizing multiple UIO sequences. The method is essentially guided by the way of minimizing the use of external coordination messages and input/output operations. Experiments are given to evaluate the proposed method.

Checking sequences for distributed test architectures

Controllability and observability problems may manifest themselves during the application of a checking sequence in a test architecture where there are multiple remote testers. These problems often require the use of external coordination message exchanges among testers during testing. However, the use of coordination messages requires the existence of an external network that can increase the cost of testing and can be difficult to implement. In addition, the use of coordination messages introduces delays and this can cause problems where there are timing constraints. Thus, sometimes it is desired to construct a checking sequence from the specification of the system under test that will be free from controllability and observability problems without requiring the use of external coordination message exchanges. This paper gives conditions under which it is possible to produce such a checking sequence, using multiple distinguishing sequences, and an algorithm that achieves this.

The design of a JADE-based autonomous workflow management system for collaborative SoC design

Given a fast changing electronics goods marketplace, designers of integrated circuits and components need to be more competitive, efficient, flexible, and use collaborative workflow to reduce time-to-market and a project’s life cycle. In recent years, agent-based workflow management systems (WfMS) have been widely used to monitor and control business design processes. In this paper, intelligent agents are applied to the collaborative system-on-chip (SoC) design environment. The proposed JADE-based autonomous workflow management system (JAWMS) uses a workflow coordination mechanism and an agent integration mechanism to enable the analysis, management and interaction of automated design processes. The workflow coordination mechanism uses five domain specific agents to perform the workflow enactment services and a generic agent to control the system flow logic. The system kernel of JAWMS follows the specifications of the workflow reference model provided by the workflow management coalition (WfMC). The agent integration mechanism supports an agent to interact with other JADE-based agent platforms and to coordinate and monitor workflow coordination messages. All agents are written in the Java language using the JADE platform and work together to perform flexible, adaptive and dynamic design tasks in an autonomous and collaborative way. JAWMS facilitates SoC design and team interaction in a collaborative but distributed product development environment.

Overcoming observability problems in distributed test architectures

The introduction of multiple remote testers to apply a test or checking sequence in a test architecture brings out the possibility of controllability and observability problems. These problems often require the use of external coordination message exchanges among testers. In this paper, we consider constructing a test or checking sequence from the specification of the system under test such that it will be free from these problems and will not require the use of external coordination messages. We give an algorithm that can check whether it is possible to construct subsequences from a given specification that eliminate the need for using external coordination message exchanges, and when it is possible actually produces such subsequences.