Hierarchical agent-based secure and reliable multicast in wireless mesh networks

We propose and analyze a hierarchical agent-based secure and reliable multicast (HASRM) algorithm for efficiently supporting secure and reliable mobile multicast in wireless mesh networks, with design considerations given to minimize the overall network cost incurred by reliable multicast packet delivery, mobility management, security key management, and group membership maintenance. HASRM dynamically maintains a group of multicast agents running on mesh routers for integrated mobility and multicast service management and leverages a hierarchical multicast structure for secure and reliable multicast data delivery. The regional service size of each multicast agent is a key design parameter. We show via model-based performance analysis and simulation validation that there exists an optimal regional service size that minimizes the overall communication cost and the optimal regional service size can be dynamically determined. We demonstrate that HASRM under optimal settings significantly outperforms traditional algorithms based on shortest-path multicast trees extended with user mobility, security, and reliability support. We also show that a variant of HASRM is superior to a recently proposed multicast algorithm for secure group communication in wireless mesh networks.     

GMAC: An overlay multicast network for mobile agent platforms

The lack of proper support for multicast services in the Internet has hindered the widespread use of applications that rely on group communication services such as mobile software agents. Although they do not require high bandwidth or heavy traffic, these types of applications need to cooperate in a scalable, fair and decentralized way. This paper presents GMAC, an overlay network that implements all multicast related functionality–including membership management and packet forwarding–in the end systems. GMAC introduces a new approach for providing multicast services for mobile agent platforms in a decentralized way, where group members cooperate in a fair way, minimize the protocol overhead, thus achieving great scalability. Simulations comparing GMAC with other approaches, in aspects such as end-to-end group propagation delay, group latency, group bandwidth, protocol overhead, resource utilization and failure recovery, show that GMAC is a scalable and robust solution to provide multicast services in a decentralized way to mobile software agent platforms with requirements similar to MoviLog.     

Design and implementation of light-weight mobile multicast for fast MIPv6

Mobile multicast is a research hotspot and can provide many applications. Some mobile multicast schemes have been proposed, but most of them introduce new entities and study construction algorithms of the dynamic multicast delivery structure which is heavyweight for wireless devices. In this paper, we propose a light-weight mobile multicast (LMM) scheme for Fast Mobile IPv6 which reduces the redundant operational overhead by simplifying multicast listener discovery (MLD) proxying. The LMM scheme implements simplified MLD proxying function on home agent to reduce the complicated multicast routing protocol and modifies MLD host part function on mobile node to reduce the multicast membership messages interaction. In order to solve the tunnel convergence problem, LMM also introduces a multicast tunnel combination and reconstruction algorithm. We set up a test-bed to evaluate the performance of LMM, and compare it with other mobile multicast schemes. The experimental results show that LMM reduces the multicast disruption time at handover. Based on the experimental results, we analyze the cost of LMM, and the results show that it has lower protocol cost than other schemes.     

组通信系统中组成员关系服务的设计和实现

在组通信系统中，成员关系的维护是一个非常重要的模块，它保证消息的次序传递和虚同步。为了使一个组中节点的数目易于扩充，采用多播树的层次结构来组织节点；当成员关系发生变化时采用一种一致性算法使得视图达到一致。在此基础上设计和实现了一个有效的组成员关系服务模块。     

An Adaptive Causal Ordering Algorithm Suited to Mobile Computing Environments

Causal message ordering is required for several distributed applications. In order to preserve causal ordering, only direct dependency information between messages, with respect to the destination process(es), need be sent with each message. By eliminating other kinds of control information from the messages, the communication overheads can be significantly reduced. In this paper we present an algorithm that uses this knowledge to efficiently enforce causal ordering of messages. The proposed algorithm does not require any prior knowledge of the network topology or communication pattern. As computation proceeds, it acquires knowledge of the communication pattern and is capable of handling dynamically changing multicast communication groups, and minimizing the communication overheads. With regard to communication overheads, the algorithm is optimal for the broadcast communication case. Extensive simulation experiments demonstrate that the algorithm imposes lower communication overheads than previous causal ordering algorithms. The algorithm can be employed in a variety of distributed computing environments. Its energy efficiency and low bandwidth requirement make it especially suitable for mobile computing systems. We show how to employ the algorithm for causally ordered multicasting of messages in mobile computing environments.     

Reliable Communication for Highly Mobile Agents

The provision of a reliable communication infrastructure for mobile agents is still an open research issue. The challenge to reliability we address in this work does not come from the possibility of faults, but rather from the mere presence of mobility, which complicates the problem of ensuring the delivery of information even in a fault-free network. For instance, the asynchronous nature of message passing and agent migration may cause situations where messages forever chase a mobile agent that moves frequently from one host to another. Current solutions rely on conventional technologies that either do not provide a solution for the aforementioned problem, because they were not designed with mobility in mind, or enforce continuous connectivity with the message source, which in many cases defeats the very purpose of using mobile agents.In this paper, we propose an algorithm that guarantees delivery to highly mobile agents using a technique similar to a distributed snapshot. A number of enhancements to this basic idea are discussed, which limit the scope of message delivery by allowing dynamic creation of the connectivity graph. Notably, the very structure of our algorithm makes it amenable not only to guarantee message delivery to a specific mobile agent, but also to provide multicast communication to a group of agents, which constitutes another open problem in research on mobile agents. After presenting our algorithm and its properties, we discuss its implementability by analyzing the requirements on the underlying mobile agent platform, and argue about its applicability.     

一种改进的移动Agent通信算法

如何实现远程Agent通信的位置透明性，保证消息不会因为目标Agent迁移而丢失，一直是移动Agent通信所面临的难题，在现有的很多移动Agent系统中都没有得到解决，作者在Mogent系统中提出的通信算法初步实现了通信的位置透明和可靠的消息传输，该文在原有处的基础上提出了一种改进的适于多种迁移和通信模式的移动Agent通信算法，进一步减少了Agent的地址注册开销和迁移受到的限制，并给出了一种避免地址欺骗攻击的解决方案。     

Spam filtering framework for multimodal mobile communication based on dendritic cell algorithm

With the continual growth of mobile devices, they become a universal portable platform for effective business and personal communication. They enable a plethora of textual communication modes including electronic mails, instant messaging, and short messaging services. A downside of such great technology is the alarming rate of spam messages that are not only annoying to end-users but raises security concerns as well. This paper presents an intelligent framework for filtering multimodal textual communication including emails and short messages. We explore a novel methodology for information fusion inspired by the human immune system and hybrid approaches of machines learning. We study a number of methods to extract and select more relevant features to reduce the complexity of the proposed model to suite mobile applications while preserving good performance. The proposed framework is intensively evaluated on a number of benchmark datasets with remarkable results achieved.     

A scalable group communication mechanism for mobile agents

Many multi-agent applications based on mobile agents require message propagation among group of agents. A fast and scalable group communication mechanism can considerably improve performance of these applications. Unfortunately, most of the existing approaches do not scale well and disseminate messages slowly when the number of agents grows.In this paper, we propose Sama, a new group communication mechanism, to speed up message delivery for a group of mobile agents on a heterogeneous internetwork. The main contribution of Sama is distribution and parallelization of message propagation in an efficient way to achieve scalability and high-speed of message delivery to group members. Sama uses message dispatcher objects (MDOs), which are stationary agents on each host, to propagate messages concurrently. The proposed mechanism is independent of agent locations and transparently delivers messages to the group using constant number of remote messages. It also transparently recovers from host failures. We also present a Hop-Ring protocol that considerably improves the performance of message dissemination in Sama. Our experimental results show that message propagation in Sama is significantly fast compared to the previously proposed methods.     

Minimal sensor activation and minimal communication in discrete-event systems

This paper is an overview of the current research on minimal sensor activation and minimal communication in discrete-event systems. In problems of sensor activation agents observing a discrete-event system can turn the sensors for their observable events on or off dynamically. In problems of communication agents observing a discrete-event system can communicate event observations to one another dynamically. In both cases, a result is that the observations made by an agent are dynamic. That is, whether or not an agent observes an event or receives a communication is dependent on other factors besides membership of certain events to certain predefined sets. We survey such problems and associated works where, additionally, the use of event sensors and communication of messages must be minimized with respect to certain criteria. The application areas considered are the diagnosis, state disambiguation and state estimation of discrete-event systems.     

A Reliable Communication Protocol for Multiregion Mobile Agent Environments

A mobile agent system is regarded as an attractive technology when developing distributed applications. However, mobility makes it more difficult to trace agents. It is also more complex for agents to communicate with each other in a reliable manner. Therefore, a reliable communication protocol is necessary to control and monitor mobile agents and deliver messages between them. In this paper, a new Reliable Communication Protocol (RCP) is proposed for a multiregion mobile agent computing environment. RCP is implemented on the ODDUGI mobile agent system. Analysis and evaluation show that RCP fulfills the following design goals: reliability, asynchrony, timeliness, location dependency, scalability, and communication cost.     

Distributed directory service and message routing for mobile agents

Research about networks and agents has identified the need for a layer that provides a uniform protocol to communicate with fixed and mobile agents. In order to preserve the compatibility with existing infrastructures, proposed solutions have involved a “home agent”, which forwards messages to a mobile entity. The mechanism of a home agent puts a burden on the infrastructure, which may hamper the scalability of the approach, in particular, in massively distributed systems, such as the amorphous computer or the ubiquitous/pervasive computing environment. Free from any compatibility constraint, we have designed an algorithm to route messages to mobile agents that does not require any fixed location. The algorithm has two different facets: a distributed directory service that maintains distributed information about the location of a mobile agent, and a message router that uses the directory service to deliver messages to a mobile agent. Two properties of the algorithm were established. Safety ensures that messages are delivered to the agent they were aimed at, whereas liveness guarantees that messages eventually get delivered. A mechanical proof of the properties was carried out using the proof assistant Coq.     

Path-Based Multicast Communication in Wormhole-Routed Unidirectional Torus Networks

This paper addresses the problem of one-to-many, or multicast, communication in wormhole-routed,n-dimensional torus networks. The proposed methods are designed for systems that support intermediate reception, which permits multidestination messages to be pipelined through several nodes, depositing a copy at each node. A key issue in the design of such systems is the routing function, which must support both unicast and multicast traffic while preventing deadlock among messages. An efficient, deadlock-free routing function is developed and used as a basis for a family of multicast algorithms. TheS-torusmulticast algorithm uses a single multidestination message to perform an arbitrary multicast operation. TheM-torusalgorithm is a generalized multiphase multicast algorithm, in which a combination of multidestination messages is used to perform a multicast in one or more communication steps. Two specific instances of the M-torus algorithm, theM_d-torusandM_u-torusmulticast algorithms, are presented. These algorithms produce contention-free multicast operations and are deadlock-free under all combinations of network traffic. A simulation study compares the performance of the different multicast algorithms, and implementation issues are discussed. The results of this research are applicable to the design of architectures for both wormhole-routed massively parallel computers and high-speed local area networks with wormhole-routed switch fabrics.     

Turn Grouping for Multicast in Wormhole-Routed Mesh Networks Supporting the Turn Model

Multicast is an important collective communication in scalable parallel computers. One efficient scheme to perform multicast is multidestination messaging[8]. In multidestination messaging, destination nodes of a multicast are partitioned into disjoint groups. Nodes in each group are reached with a multidestination message that conforms to the base routing algorithm of the system. A systematic way of partitioning the nodes is critical to the efficiency of multidestination messaging. In this paper we propose a node grouping method, called turn grouping, for partitioning the destination nodes in a multicast. Turn grouping is general in the sense that it supports any base routing algorithm derivable from the turn model [5]. Given such a base routing algorithm and the corresponding prohibited turns, turn grouping can systematically produce a proper schedule for multicasting the message. We evaluated the performance of turn grouping using three typical turn model-based routing algorithms. The simulation results show that our approach performs better than the Umesh [12] and the Hamiltonian-path [8] algorithms.     

移动Agent通信技术的研究与分析

本文研究和分析了移动Agent系统中常见的四个通信技术问题。这四个问题分别是:移动Agent的命名,移动Agent的定位,移动Agent的消息处理及移动Agent通信可靠性。     

Dynamic group communication

Group communication is the basic infrastructure for implementing fault-tolerant replicated servers. While group communication is well understood in the context of static groups (in which the membership does not change), current specifications of dynamic group communication (in which processes can join and leave groups during the computation) have not yet reached the same level of maturity. The paper proposes new specifications – in the primary partition model – for dynamic reliable broadcast (simply called “reliable multicast”), dynamic atomic broadcast (simply called “atomic multicast”) and group membership. In the special case of a static system, the new specifications are identical to the well known static specifications. Interestingly, not only are these new specifications “syntactically” close to the static specifications, but they are also “semantically” close to the dynamic specifications proposed in the literature. We believe that this should contribute to clarify a topic that has always been difficult to understand by outsiders. Finally, the paper shows how to solve atomic multicast, group membership and reliable broadcast. The solution of atomic multicast is close to the (static) atomic broadcast solution based on reduction to consensus. Group membership is solved using atomic multicast. Reliable multicast can be efficiently solved by relying on a thrifty generic multicast algorithm. Andrée Schiper graduated in Physics from the ETHZ in Zurich in 1973 and received the PhD degree in Computer Science from the EPFL (Federal Institute of Technology in Lausanne, Switzerland) in 1980. He has been a professor of computer science at EPFL since 1985, leading the Distributed Systems Laboratory. During the academic year 1992–1993, he was on sabbatical leave at the University of Cornell, Ithaca, New York, and in 2004-2005 at the Ecole Polytechnique near Paris. His research interests are in the area of dependable distributed systems, middleware support for dependable systems, replication techniques (including for database systems), group communication, distributed transactions, and, recently MANETs (mobile ad-hoc networks). From 2000 to 2002, he was the chair of the steering committee of the International Symposium on Distributed Computing (DISC). He has taken part in several European projects. He is currently a member of the editorial board of Distributed Computing, and of IEEE Transactions on Dependable and Secure Computing.     

A reliable multicast protocol for distributed mobile systems:design and evaluation

Reliable multicast is a powerful communication primitive for structuring distributed programs in which multiple processes must closely cooperate together. We propose a protocol for supporting reliable multicast in a distributed system that includes mobile hosts and evaluate the performance of our proposal through simulation We consider a scenario in which mobile hosts communicate with a wired infrastructure by means of wireless technology. Our proposal provides several novel features. The sender of each multicast may select among three increasingly strong delivery ordering guarantees: FIFO, causal, total. Movements do not trigger the transmission of any message in the wired network as no notion of hand-off is used. The set of senders and receivers (group) may be dynamic. The size of data structures at mobile hosts, the size of message headers, and the number of messages in the wired network for each multicast are all independent of the number of group members. The wireless network is assumed to provide only incomplete spatial coverage and message losses could occur even within cells. Movements are not negotiated and a mobile host that leaves a cell may enter any other cell, perhaps after a potentially long disconnection. The simulation results show that the proposed protocol has good performance and good scalability properties     

Capacity-aware multicast algorithms on heterogeneous overlay networks

The global deployment of IP multicast has been slow due to the difficulties related to heterogeneity, scalability, manageability, and lack of a robust interdomain multicast routing protocol. Application-level multicast becomes a promising alternative. Many overlay multicast systems have been proposed in recent years. However, they are insufficient in supporting applications that require any-source multicast with varied host capacities and dynamic membership. In this paper, we propose two capacity-aware multicast systems that focus on host heterogeneity, any source multicast, dynamic membership, and scalability. We extend Chord and Koorde to be capacity-aware. We then embed implicit degree-varying multicast trees on top of the overlay network and develop multicast routines that automatically follow the trees to disseminate multicast messages. The implicit trees are well balanced with the workload evenly spread across the network. We rigorously analyze the expected performance of multisource capacity-aware multicasting, which was not thoroughly addressed in any previous work. We also perform extensive simulations to evaluate the proposed multicast systems.