Optimizing responses to broadcast messages in radio networks

Algorithms to optimize the performance of response traffic for broadcast messages in a packet-switched radio network are studied. The situation considered here involves a source node sending a broadcast message to all destinations and collecting positive response packets from these destinations in a fully connected packet radio network. The exact value of the number of destination nodes is unknown. A contention-based two-level protocol is described. Based on the protocol, an optimization problem is formulated in order to minimize the time for the source node to receive all the responses. Several algorithms are presented and numerical results of the corresponding optimization problems are obtained. These optimization problems are treated by the methods of dynamic programming. An extension of the basic scheme—multicast instead of full broadcast message—is also studied.     

Optimizing responses to broadcast messages in radio networks

Algorithms to optimize the performance of response traffic for broadcast messages in a packet-switched radio network are studied. The situation considered here involves a source node sending a broadcast message to all destinations and collecting positive response packets from these destinations in a fully connected packet radio network. The exact value of the number of destination nodes is unknown. A contention-based two-level protocol is described. Based on the protocol, an optimization problem is formulated in order to minimize the time for the source node to receive all the responses. Several algorithms are presented and numerical results of the corresponding optimization problems are obtained. These optimization problems are treated by the methods of dynamic programming. An extension of the basic scheme—multicast instead of full broadcast message—is also studied.This work was supported by the US Army Research Office under Contract No. DAAG29-84-K-0084.     

Atomic broadcast in asynchronous crash-recovery distributed systems and its use in quorum-based replication

Atomic broadcast is a fundamental problem of distributed systems: It states that messages must be delivered in the same order to their destination processes. This paper describes a solution to this problem in asynchronous distributed systems in which processes can crash and recover. A consensus-based solution to atomic broadcast problem has been designed by Chandra and Toueg for asynchronous distributed systems where crashed processes do not recover. We extend this approach: it transforms any consensus protocol suited to the crash-recovery model into an atomic broadcast protocol suited to the same model. We show that atomic broadcast can be implemented requiring few additional log operations in excess of those required by the consensus. The paper also discusses how additional log operations can improve the protocol in terms of faster recovery and better throughput. To illustrate the use of the protocol, the paper also describes a solution to the replica management problem in asynchronous distributed systems in which processes can crash and recover. The proposed technique makes a bridge between established results on weighted voting and recent results on the consensus problem.     

Quorum-based power-saving multicast protocols in the asynchronous ad hoc network

The asynchronous PS (Power-Saving) unicast protocol was designed for two PS wireless hosts to transmit the unicast message in the ad hoc network even their clocks are asynchronous. However, as regard to transmit a multicast message among more than two PS hosts, the protocol could not guarantee that all PS hosts can wake up at the same time. Some PS hosts may be in the PS mode when the multicast message is transmitted. Thus, the multicast message should be retransmitted again and again until all PS hosts receive the message. It will increase the energy consumption and the usage of the bandwidth. In this paper, we propose quorum-based PS multicast protocols for PS hosts to transmit multicast messages in the asynchronous ad hoc network. In those protocols, PS hosts use quorums to indicate their wakeup patterns. We introduce the rotation m-closure property to guarantee that m different quorums have the intersection even quorums are rotated due to asynchronous clocks. Thus, m PS hosts adopting m quorums satisfying the rotation m-closure property could wake up simultaneously and receive the multicast message even their clocks are asynchronous. We propose two quorum systems named the uniform k-arbiter and the CRT (Chinese Remainder Theorem) quorum system, which satisfy the rotation m-closure property. As shown in our analysis results, our quorum-based PS multicast protocols adopting those quorum systems can save more energy to transmit multicast messages.     

Deadlock-free multicast wormhole routing in 2-D mesh multicomputers

Multicast communication services, in which the same message is delivered from a source node to an arbitrary number of destination nodes, are being provided in new-generation multicomputers. Broadcast is a special case of multicast in which a message is delivered to all nodes in the network. The nCUBE-2, a wormhole-routed hypercube multicomputer, provides hardware support for broadcast and a restricted form of multicast in which the destinations form a subcube. However, the broadcast routing algorithm adopted in the nCUBE-2 is not deadlock-free. In this paper, four multicast wormhole routing strategies for 2-D mesh multicomputers are proposed and studied. All of the algorithms are shown to be deadlock-free. These are the first deadlock-free multicast wormhole routing algorithms ever proposed. A simulation study has been conducted that compares the performance of these multicast algorithms under dynamic network traffic conditions in a 2-D mesh. The results indicate that a dual-path routing algorithm offers performance advantages over tree-based, multipath, and fixed-path algorithms     

Broadcast protocols for distributed systems

An innovative approach is presented to the design of fault-tolerant distributed systems that avoids the several rounds of message exchange required by current protocols for consensus agreement. The approach is based on broadcast communication over a local area network, such as an Ethernet or a token ring, and on two novel protocols, the Trans protocol, which provides efficient reliable broadcast communication, and the Total protocol, which with high probability promptly places a total order on messages and achieves distributed agreement even in the presence of fail-stop, omission, timing, and communication faults. Reliable distributed operations, such as locking, update, and commitment, typically require only a single broadcast message rather than the several tens of messages required by current algorithms     

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     

An optimal scheduling algorithm for an agent-based multicast strategy on irregular networks

This paper describes an agent-based approach for scheduling multiple multicast on wormhole switch-based networks with irregular topologies. Multicast/broadcast is an important communication pattern, with applications in collective communication operations such as barrier synchronization and global combining. Our approach assigns an agent to each subtree of switches such that the agents can exchange information efficiently and independently. The entire multicast problem is then recursively solved with each agent sending message to those switches that it is responsible for. In this way, communication is localized by the assignment of agents to subtrees. This idea can be easily generalized to multiple multicast since the order of message passing among agents can be interleaved for different multicasts. The key to the performance of this agent-based approach is the message-passing scheduling between agents and the destination processors. We propose an optimal scheduling algorithm, called ForwardInSwitch to solve this problem. We conduct extensive experiments to demonstrate the efficiency of our approach by comparing our results with SPCCO, a highly efficient multicast algorithm reported in literature. We found that SPCCO suffers link contention when the number of simultaneous multiple multicast becomes large. On the other hand, our agent-based approach achieves better performance in large cases.     

快速响应的高效多值拜占庭共识方案

由于网络设备的增多和传输环境的不确定性,消息时延同样具有不确定性,异步共识协议发挥出更多优势.Miller等于2016年提出第一个异步共识协议HoneyBadgerBFT,但其在实现高吞吐量的同时传输效率依然可以再优化.针对HoneyBadgerBFT中的广播协议进行改进,减少广播过程中的消息复杂度,同时增加可选的消息...     

基于服务器转发的支持多种通信方式的通信协议

提出了一种基于服务器转发的通信协议，其能够支持广播、组播、单播这几种通信方式，支持多种类型消息的通信。介绍了该协议的功能、报文格式以及实现方法。     

A total ordering multicast protocol using propagation trees

The paper discusses a multicast mechanism using propagation trees. It guarantees the total ordering (including causal ordering) of messages in multiple groups. The mechanism introduces a concept of meta-groups (a subset of a multicast group) and organizes meta-groups into propagation trees. Compared with the existing propagation tree mechanisms, this mechanism has the following advantages: 1) Greater parallelism. Messages can be sent to destinations by using broadcast networks. 2) Less message cost and less latency time. It takes less network communication to multicast a message and less time to have the message delivered to all the destinations. 3) More flexibility to dynamic membership changes and higher reliability for message propagation. It does not need to restructure propagation trees when there is a change in membership, and a site failure does not stop the message propagation to its descendants in the tree     

Optimal software multicast in wormhole-routed multistage networks

Multistage interconnection networks are a popular class of interconnection architecture for constructing scalable parallel computers (SPCs). The focus of this paper is on the multistage network system which supports wormhole routed turnaround routing. Existing machines characterized by such a system model include the IBM SP-1 and SP-2, TMC CM-5, and Meiko CS-2. Efficient collective communication among processor nodes is critical to the performance of SPCs. A system-level multicast service, in which the same message is delivered from a source node to an arbitrary number of destination nodes, is fundamental in supporting collective communication primitives including the application-level broadcast, reduction, and barrier synchronization. This paper addresses how to efficiently implement multicast services in wormhole-routed multistage networks, in the absence of hardware multicast support, by exploiting the properties of the turnaround switching technology. An optimal multicast algorithm is proposed. The results of implementations on a 64-node SP-1 show that the proposed algorithm significantly outperforms the application-level broadcast primitives provided by currently existing collective communication libraries including the public domain MPI     

一种基于TTCB的容侵原子多播协议研究*

对基于可信实时计算基（TTCB）的分布式容侵系统的体系结构进行了研究,针对分布式容侵系统中的一致性问题,实现了利用TTCB服务的容侵原子多播协议。在进程总数大于两倍恶意进程个数的条件下,该协议可以满足正确结果的一致性要求,达到了入侵容忍的目的。最后证明了该协议算法的正确性。     

Multicast communication in multicomputer networks

Efficient routing of messages is a key to the performance of multicomputers. Multicast communication refers to the delivery of the same message from a source node to an arbitrary number of destination nodes. While multicast communication is highly demanded in many applications, most of the existing multicomputers do not directly support this service; rather it is indirectly supported by multiple one-to-one or broadcast communications, which result in more network traffic and a waste of system resources. The authors study routing evaluation criteria for multicast communication under different switching technologies. Multicast communication in multicomputers is formulated as a graph theoretical problem. Depending on the evaluation criteria and switching technologies, they study three optimal multicast communication problems, which are equivalent to the finding of the following three subgraphs: optimal multicast path, optimal multicast cycle, and minimal Steiner tree, where the interconnection of a multicomputer defines a host graph. They show that all these optimization problems are NP-complete for the popular 2D-mesh and hypercube host graphs. Heuristic multicast algorithms for these routing problems are proposed     

Unicast-based fault-tolerant multicasting in wormhole-routed hypercubes

A unicast-based fault-tolerant multicasting method is proposed for hypercubes, which can still work well when the system contains enough faults. A multicast message may be unable to reach a destination if Hamming distance between the destination and the multicast source is large enough. A multicast message fails if any one of the destinations is unreachable from the source. An effective destination ordering scheme of the destinations is proposed for one-port systems first, it is extended to all-port systems for unicast-based fault-tolerant multicasting. Unreachable destinations from the source based on the local safety information are forwarded to a reachable destination, where the multicast message can be routed reliably. Destination ordering is completed based on Hamming distance. A multiple round p-cube routing scheme is presented for a deadlock-free fault-tolerant routing for each unicast step in hypercubes, where the same virtual channel is used for each round of p-cube routing. Sufficient simulation results are presented by comparing with the previous methods.     

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.     

Secure reliable multicast protocols in a WAN

Summary. A secure reliable multicast protocol enables a process to send a message to a group of recipients such that all correct destinations receive the same message, despite the malicious efforts of fewer than a third of the total number of processes, including the sender. This has been shown to be a useful tool in building secure distributed services, albeit with a cost that typically grows linearly with the size of the system. For very large networks, for which this is prohibitive, we present two approaches for reducing the cost: First, we show a protocol whose cost is on the order of the number of tolerated failures. Secondly, we show how relaxing the consistency requirement to a probabilistic guarantee can reduce the associated cost, effectively to a constant. Received: August 1997 / Accepted: July 1999     

基于NS2的组播路由协议实现及仿真

组播是一个源节点将同一信息传送到多个目的节点的通信方式,IP组播技术减少了网络不必要的带宽开销、网络资源的消耗以及大大减轻了源主机的负担。网络仿真是网络研究者验证网络协议在各种情况下是否具有健壮性和可靠性的有效手段。NS2是面向对象的大型离散事件仿真器,它不仅能实现复杂的网络数据传输和拓扑结构的仿真,还能近乎真实地模拟各种IP网络环境。用NS2实现了一个20个节点网络拓扑的组播路由协议PIM—SM仿真,并获取数据对PIM—SM组播网络性能进行了分析。仿真结果表明了组播网络性能的优越性。     

Multicasting in the presence of aggregated deliveries

An increasing number of distributed systems relies on forms of message correlation, which result in atomic delivery of multiple messages aggregated by following process-specific criteria. Generally, more than one process is aggregating messages, implying that messages are multicast. While delivery guarantees for multicast scenarios with single message delivery are well understood, existing systems and models for aggregated deliveries either consider only unicast, centralized setups, or focus on efficiency thus providing only best-effort guarantees. This paper investigates the foundations of Multi-Delivery Multicast (MDMcast) in asynchronous distributed systems with crash-stop failures. We first describe a succinct aggregation model with a concise and generic predicate grammar for expressing conjunctions on messages and properties for a corresponding multicast primitive, which we term Conjunction-MDMcast (C-MDMcast). We show that for processes interested in identical conjunctions to achieve agreement on delivered messages, a total order on individual messages (or equivalent oracle) is not only useful but necessary, which is clearly opposed to single-message deliveries. We show this indirectly by exhibiting an algorithm implementing C-MDMcast on top of Total Order Broadcast (TOBcast) and vice-versa for a majority of correct processes. Then, we extend our predicate grammar with disjunctions, leading to the specification of Disjunction-MDMcast (D-MDMcast). We exhibit an algorithm implementing D-MDMcast, derived from our algorithm implementing C-MDMcast. We formalize several additional properties for both of our specifications, including ordering properties on aggregated messages and a notion of agreement capturing non-identical yet “related” conjunctions, and show how our respective algorithms implement these.     

Ad-hoc网络组播路由协议的研究与设计

从无线自组网实际环境应用出发,提出了一种极大节省通信带宽并且实现简单的无线自组网组播路由协议.该协议充分利用了无线信道的广播特性,采用广播方式完成对网络内各节点的组播数据的分发,网络内各节点则根据组播数据的目的地址来判断是否应向自己直连的组播成员转发组播数据,并根据序列号决定是否将该组播数据再次广播出去以及防止收到重复的组播数据,因该协议不使用组播树,省却了建立与重建组播树的复杂过程,从而保证了对通信带宽的节省与实现的简便.现已在PowerPC平台上得到实际验证,运行效果良好.