带有消息投递概率估计的机会网络自适应缓存管理策略

高效的缓存管理策略能够有效提高机会网络中节点的缓存资源利用率。消息的投递概率直接决定了消息的转发与存储必要性,该文提出一种带有消息投递概率估计的自适应缓存管理策略,通过构建节点连接状态分析模型,以分布式的方式感知节点服务能力,从而估计消息的投递概率,进而确定消息的转发与删除优先级,以执行缓存管理相关操作。结果表明,所提出的缓存管理策略可降低网络负载57%,并有效提高消息的成功投递率,降低消息的平均投递时延。     

Extension of Delay Tolerant Network’s Routing Protocols for Preventing Excessive Utilization of Resources

The routing algorithms of DTN have the inbuilt storage management scheme such as Hop based TTL (Spray and Wait) or passive cure (Potential-based Entropy Adaptive Routing PEAR). There has been a significant amount of work in the past regarding buffer management policies. In this paper, we have proposed a new message deletion policy for multi-copy routing schemes. In this scheme, message delivery information is communicated to the other nodes in the network for removing useless bundles from the network, which prevents the nodes from the buffer overflow problem and avoid transfer of useless message replicas thus relaxing the resources of the nodes. We evaluate our proposed method by simulating network, on four major DTNs routing algorithms: Epidemic, Spray and Wait, ProPHET and MaxProp. The simulation results clearly show significant improvement in the value of delivery probability and the overhead ratio for an Epidemic, Spray and Wait, and Prophet routing protocols.     

Early detection and rejection probability‐based congestion control scheme for deep space networks

Deep Space Networks (DSNs) are a class of DTNs. In such networks, owing to limited radio range and node mobility, end‐to‐end paths between source and destination nodes are not available. Messages are relayed by store‐and‐forward strategy and may be buffered for long periods before being forwarded to the next hop. Therefore, the buffer of message carriers may overflow, and congestion follows. To address this issue, this paper proposes an early detection and rejection probability‐based congestion control algorithm, named ERBA, in which every intermediate node estimates rejection probability when a new message arrives and refuses to receive the message with the rejection probability, so as to avoid congestion. To validate its effectiveness, ERBA is merged into static routing (SR) and dynamic routing (DR). SR and DR are classical routing algorithms for DSNs. The simulation results show that when working with ERBA, the routing overhead of SR and DR decreases rapidly. However, the message delivery ratio also decreases. To deal with this problem, we propose a buffer‐compensation mechanism that effectively reduces the routing overhead for SR and DR without causing the reduction of the message delivery ratio.Copyright © 2014 John Wiley & Sons, Ltd.     

Message Drop Control Buffer Management Policy for DTN Routing Protocols

In delay tolerant network interruptions will occur continuously because there is no end-to-end path exists for the longer period of time from source to destination. In this context, delays can be immensely large due to its environment contrails e.g. wildlife tracking, sensor network, deep space and ocean networks. Furthermore, larger replication of messages put into the network is to increase delivery probability. Due to this high buffer occupancy storage space and replication result in a huge overhead on the network. Consequently, well-ordered intelligent message control buffer drop policies are necessary to operate on buffer that allows control on messages drop when the node buffers are near to overflow. In this paper, we propose an efficient buffer management policy which is called message drop control source relay (MDC-SR) for delay tolerant routing protocols. We also illustrate that conventional buffer management policy like Drop oldest, LIFO and MOFO be ineffective to consider all appropriate information in this framework. The proposed MDC-SR buffer policy controls the message drop while at the same time maximizes the delivery probability and buffer time average and reduces the message relay, drop and hop count in the reasonable amount. Using simulations support on an imitation mobility models Shortest Path Map Based Movement and Map Route Movements, we show that our drop buffer management MDC-SR with random message sizes performs better as compared to existing MOFO, LIFO and DOA.     

延迟容忍移动传感器网络中基于概率复制的数据传输策略及其性能研究

该文提出了一种基于概率复制的数据传输策略PRD(Probability Replication Delivery scheme)用于空间中间断连通的延迟容忍移动传感器网络(DTMSN)数据传输。PRD由选择复制策略和队列管理组成,前者根据节点将消息传递给汇聚点的可能性,选择下一跳进行复制传输;队列管理则利用引入传输概率及复制数的消息生存时间决定队列中消息丢弃原则。仿真分析表明,与现有的几种数据传输策略相比,PRD能以较低的数据复制数及传输延迟获得较高的数据传输成功率。     

Enhanced fuzzy logic‐based spray and wait routing protocol for delay tolerant networks

Delay tolerant networks are a class of ad hoc networks that enable data delivery even in the absence of end‐to‐end connectivity between nodes, which is the basic assumption for routing in ad hoc networks. Nodes in these networks work on store‐carry and forward paradigm. In addition, such networks make use of message replication as a strategy to increase the possibility of messages reaching their destination. As contact opportunities are usually of short duration, it is important to prioritize scheduling of messages. Message replication may also lead to buffer congestion. Hence, buffer management is an important issue that greatly affects the performance of routing protocols in delay tolerant networks. In this paper, Spray and Wait routing protocol, which is a popular controlled replication‐based protocol for delay tolerant networks, has been enhanced using a new fuzzy‐based buffer management strategy Enhanced Fuzzy Spray and Wait Routing, with the aim to achieve increased delivery ratio and reduced overhead ratio. It aggregates three important message properties namely number of replicas of a message, its size, and remaining time‐to‐live, using fuzzy logic to determine the message priority, which denotes its importance with respect to other messages stored in a node's buffer. It then intelligently selects messages to schedule when a contact opportunity occurs. Because determination of number of replicas of a message in the network is a difficult task, a new method for estimation of the same has been proposed. Simulation results show improved performance of enhanced fuzzy spray and wait routing in terms of delivery ratio and resource consumption. Copyright © 2014 John Wiley & Sons, Ltd.     

机会网络中消息冗余度动态估计的缓存管理策略

机会网络以存储-携带-转发的方式实现节点间通信,高效的节点缓存管理策略能够充分利用有限的缓存空间。该文提出了一种基于消息冗余度动态估计的自适应缓存管理机制,利用消息携带节点的活跃程度和当前网络状态下消息副本数量,预测给定消息的投递状态,节点以消息冗余程度为参数确定消息的转发以及携带优先级。结果表明,所提出的节点活跃度和消息副本数的估计方法比较准确,同时所提出的缓存管理策略能有效提高消息成功投递率,降低网络平均时延和网络负载率。     

Energy Efficient Forwarding Algorithm in Opportunistic Networks

In opportunistic networks,a successful message transmission between node pairs depends on the message size,the transmission speed and the connection duration time.This paper proposes a new message forwarding algorithm to improve the message delivery ratio and reduce the energy consumption.Previous encounter characteristics between nodes are used to estimate future connection duration time using a three point estimation method.Furthermore,the buffer utilization of nodes is used as a weight for the likelihoods to meet destinations according to the hop count of messages stored in the buffer.The simulation results show that the proposed forwarding algorithm achieves higher delivery ratio and less overhead ratio than the other four popular routing protocols.In addition,the proposed algorithm gains a better average residual energy performance among all the compared protocols.     

Deadlock Avoidance in Store-and-Forward Networks--II: Other Deadlock Types

This paper describes the construction of loop-free buffer graphs which avoid four types of buffer deadlocks in store-and-forward networks. 1) Progeny deadlock, where original messages spawnother ones, and buffer contention occurs between the original and progeny messages. This occurs when positive or negative acknowledgments are created, e.g., if messages reverse direction after encountering a path failure. 2) Copy-release deadlock, where a message copy is stored at the source node and the buffer is not released until an acknowledgment is received from the destination node. Buffer contention may arise among the original messages, stored copies, and acknowledgments. 3) Pacing deadlock, where a local flow control protocol is used between a network node and attached terminals. Buffer contention may arise between the message flows into and out of the terminal, preventing the transmission of go-ahead commands. 4) Reassembly deadlock, whereby reassembly of packetized messages at the destination node cannot be completed. The solution presented here has the novel features of not requiring preallocation of reassembly buffers before transmission of multiple packets of a multipacket message, and not requiring dedication of buffer space at intermediate nodes for individual messages. These schemes are believed to have modest buffer requirements at each node, and if adequate buffer pools are provided, will incur negligible performance degradations under normal conditions, with overhead increasing under heavy buffer usage when deadlock is near.     

Fuzzy Logic Based Distance and Energy-Aware Routing Protocol in Delay-Tolerant Mobile Sensor Networks

In challenged networks such as Wireless Sensor Networks, limitations such as nodes mobility, short radio range and sparse network density can prevent communications among nodes. Consequently, it can result in long delays in exchanging messages among nodes. Designing Delay-Tolerant Networks is considered to be an approach for dealing with lengthy breakdown of communication between nodes. Using multi-replica methods seems rational for these networks. However, a majority of these methods inject a large amount of replications of a message in the network so as to enhance message delivery probability which consequently leads to the loss of energy and reduction of network efficiency. Two major issues should be considered to achieve data delivery in such challenging networking environments: a routing strategy for the network and a buffer management policy. This study proposes a new routing protocol called Fuzzy-Logic based Distance and Energy Aware Routing protocol (FLDEAR) in delay tolerant mobile sensor network. A FLDEAR is a distance and energy aware protocol that reduces the number of message replications and uses two fuzzy inference systems in routing and buffer management. The results of conducted simulations indicated that this routing algorithm can be used for enhancing data packet delivery ratios and reducing data transmission overhead than several current Delay-Tolerant Mobile Sensor Networks routing protocols.     

Addressing space‐constraint driven selfishness in smart opportunistic environment

A smart opportunistic environment is a physical space, which allows the smart physical objects to communicate in the presence of disruption in connectivity. Because, the objects in such an environment are buffer constrained, some of the objects will not participate in data forwarding, when there is scarcity of storage (buffer) space. In this paper, we focus on such selfish behavior of objects triggered by space constraints in a smart opportunistic environment. We propose a novel data forwarding algorithm, selfishness and buffer‐aware routing (SBR), in which a node is chosen as a relay, based on its capability, which is a function of its available buffer space and past encounter history (delivery predictability) with the destination. SBR can efficiently utilize the limited buffer space in a node with a buffer management scheme, WSD. It can also detect space constraint driven selfish behavior of nodes and resolve it using a reputation‐based technique, MSD. We have conducted simulation using both synthetic and real‐world traces for evaluating our proposed SBR algorithm. For analyzing the performance of the algorithm in real‐time, a smart vehicular test‐bed is developed. Simulation results and test‐bed implementation show that our algorithm performs better in terms of higher delivery ratio, lower overhead ratio, and lower delivery delay, compared with existing opportunistic data forwarding algorithms.     

Integrated Social and QoS Trust-Based Routing in Delay Tolerant Networks

We propose and analyze a class of integrated social and quality of service (QoS) trust-based routing protocols in mobile ad-hoc delay tolerant networks. The underlying idea is to incorporate trust evaluation in the routing protocol, considering not only QoS trust properties but also social trust properties to evaluate other nodes encountered. We prove that our protocol is resilient against bad-mouthing, good-mouthing and whitewashing attacks performed by malicious nodes. By utilizing a stochastic Petri net model describing a delay tolerant network consisting of heterogeneous mobile nodes with vastly different social and networking behaviors, we analyze the performance characteristics of trust-based routing protocols in terms of message delivery ratio, message delay, and message overhead against connectivity-based, epidemic and PROPHET routing protocols. The results indicate that our trust-based routing protocols outperform PROPHET and can approach the ideal performance obtainable by epidemic routing in delivery ratio and message delay, without incurring high message overhead. Further, integrated social and QoS trust-based protocols can effectively trade off message delay for a significant gain in message delivery ratio and message overhead over traditional connectivity-based routing protocols.     

Dynamics of TCP traffic over ATM networks

Investigates the performance of transport control protocol (TCP) connections over ATM networks without ATM-level congestion control and compares it to the performance of TCP over packet-based networks. For simulations of congested networks, the effective throughput of TCP over ATM can be quite low when cells are dropped at the congested ATM switch. The low throughput is due to wasted bandwidth as the congested link transmits cells from “corrupted” packets, i.e., packets in which at least one cell is dropped by the switch. The authors investigate two packet-discard strategies that alleviate the effects of fragmentation. Partial packet discard, in which remaining cells are discarded after one cell has been dropped from a packet, somewhat improves throughput. They introduce early packet discard, a strategy in which the switch drops whole packets prior to buffer overflow. This mechanism prevents fragmentation and restores throughput to maximal levels     

A fuzzy logic based buffer management scheme with traffic differentiation support for delay tolerant networks

Delay tolerant networks (DTNs) are an emerging class of wireless networks which enable data delivery even in the absence of end-to-end connectivity. Under these circumstances, message replication may be applied to increase the delivery ratio. The requirement of long term storage and message replication puts a burden on network resources such as buffer and bandwidth. Buffer management is an important issue which greatly affects the performance of routing protocols in DTNs. Two main issues in buffer management are drop decision when buffer overflow occurs and scheduling decision when a transmission opportunity arises. The objective of this paper is to propose an enhancement to the Custom Service Time Scheduling traffic differentiation scheme by integrating it with a fuzzy based buffer ranking mechanism based on three message properties, namely, number of replicas, message size and remaining time-to-live. It uses fuzzy logic to determine outgoing message order and to decide which messages should be discarded within each traffic class queue. Results of simulation study show that the proposed fuzzy logic-based traffic differentiation scheme achieves improved delivery performance over existing traffic differentiation scheme for DTNs.     

Impact of Bloom Filter on Infection Rate in Epidemic Forwarding for ICNs

Mobile ad hoc routing protocols fails in intermittently connected networks (ICN) (i.e. characterized by short-range communication and absence of connected path from source to destination). However, Epidemic routing techniques ensures eventual message delivery from source to destination even where there is never a connected path or when a network partition exists at the origin of message. Epidemic Routing uses random pair-wise messages exchanges between nodes with goals to maximize message delivery rate, minimize message latency, and the total resources consumed in message delivery. Epidemic routing uses summary vector to avoid useless transmission and redundancy. Further,to make summery vector efficient, epidemic routing can use bloom filter to significantly reduce the useless transmissions associated with the summary vector. However, the challenge for epidemic routing remains opens is to optimal design of summary vector size for finite buffer while keeping the benefits of infinite buffer space. This paper proposes an improved scheme of Bloom filter (named it modified bloom filter MBLF), which is tailored according to epidemic routing. We performed simulation to support our clam and observed that delivery ratio of MBLF with epidemic routing is 19 % higher then the traditional bloom filter. In this paper, we have proposed a bloom filter based epidemic forwarding for ICNs.     

Socially-aware routing for publish-subscribe in delay-tolerant mobile ad hoc networks

Applications involving the dissemination of information directly relevant to humans (e.g., service advertising, news spreading, environmental alerts) often rely on publish-subscribe, in which the network delivers a published message only to the nodes whose subscribed interests match it. In principle, publish- subscribe is particularly useful in mobile environments, since it minimizes the coupling among communication parties. However, to the best of our knowledge, none of the (few) works that tackled publish-subscribe in mobile environments has yet addressed intermittently-connected human networks. Socially-related people tend to be co-located quite regularly. This characteristic can be exploited to drive forwarding decisions in the interest-based routing layer supporting the publish-subscribe network, yielding not only improved performance but also the ability to overcome high rates of mobility and long-lasting disconnections. In this paper we propose SocialCast, a routing framework for publish-subscribe that exploits predictions based on metrics of social interaction (e.g., patterns of movements among communities) to identify the best information carriers. We highlight the principles underlying our protocol, illustrate its operation, and evaluate its performance using a mobility model based on a social network validated with real human mobility traces. The evaluation shows that prediction of colocation and node mobility allow for maintaining a very high and steady event delivery with low overhead and latency, despite the variation in density, number of replicas per message or speed.     

<Emphasis Type="BoldItalic">LAMA/CA</Emphasis>: A Load-Adaptive MAC Protocol for Short Packets

An efficient Media Access Control (MAC) protocol for wireless Internet access is developed in this study. The proposed access protocol exploits the fact that very often the Internet access messages, such as HTTP download requests, are based on short packets. In addition, whenever the user is able to access to multiple overlapping base stations (e.g., in WiMAX access networks, or in 3GPP cellular networks), the proposed protocol enables the user to select the least loaded base station. Consequently, the user gets a better quality of service, while load balancing is achieved by preferring links that are less loaded over congested links. The key idea is to adjust the access probability to the load on the local link, and to use a different access protocol for short messages. Delay insensitive and long messages are transmitted using a Request To Send (RTS) and Clear To Send (CTS) mechanism, in a similar way to IEEE 802.11, over hops that are able to support this protocol type, while short and delay-sensitive messages are transmitted using another method, that offers a reduced call delivery delay, as well as better channel utilization. Whenever the message length drops below a certain threshold (evaluated in this study), the overhead of transmitting an RTS and CTS messages becomes too large. The analysis in this study shows that this threshold is load-dependent. Whenever the message length drops below this load-dependent threshold, this study proposes to use a protocol which is more efficient for short messages transmissions, such as HTTP download requests, Short Message Service (SMS) messages, and signaling messages. The proposed MAC protocol is especially suitable for 3G and beyond cellular networks. Whenever there are number of channels that can be possibly used to deliver a message, it enables to select the least loaded channel among several channels.     

Neural network‐based routing protocol for opportunistic networks with intelligent water drop optimization

Opportunistic Networks (OppNets) is a system of wirelessly connected nodes in a varying network topology. Routing in OppNets is a challenge. To overcome the problem of routing, an intelligent dynamic strategy to select next best node for forwarding a message is required. This paper proposes an intelligent routing mechanism based on Intelligent Water Drop (IWD) Algorithm which is used in tandem with Neural Networks (NNs) as an optimization technique to solve the problem of routing in such networks. The nature–inspired IWD algorithm provides robustness, whereas the neural network base of the algorithm helps it to make intelligent routing decisions. The weights in the Neural Network model are calculated by IWD Algorithm using training data consisting of inputs that are characteristic parameters of nodes, such as buffer space, number of successful deliveries and energy levels along with transitive parameters such as delivery probabilities. The proposed protocol Intelligent Water Drop Neural Network (IWDNN) is compared with other protocols that use similar ideologies such as MLProph, K‐nearest neighbour classification based routing protocol (KNNR), Cognitive Routing Protocol for Opportunistic Network (CRPO), and Inheritance Inspired Context Aware Routing Protocol (IICAR), as well as the standard protocol Prophet. IWDNN is shown to outperform all other protocols with an average message delivery ratio of 60%, which is a significant improvement of over 10% in comparison to other similarly conceived algorithms. It has one of the lowest latency among the protocols studied, in a range of 3000 to 4000 s, and incurs comparably low overhead costs in the range of 15 to 30. The drop ratios are one of the lowest, staying near six and approaching zero as buffer size is increased. Average amount of time a message stayed in the buffer was the lowest, with a mean of 1600 s.     

Building reliable mobile‐aware applications using the Rover toolkit

This paper discusses extensions to the Rover toolkit for constructing reliable mobile‐aware applications. The extensions improve upon the existing failure model, which addresses client or communication failures and guarantees reliable message delivery from clients to server, but does not address server failures (e.g., the loss of an incoming message due to server failure) (Joseph et al., 1997). Due to the unpredictable, intermittent communication connectivity typically found in mobile client environments, it is inappropriate to make clients responsible for guaranteeing request completion at servers. The extensions discussed in this paper provide both system‐ and language‐level support for reliable operation in the form of stable logging of each message received by a server, per‐application stable variables, programmer‐supplied failure recovery procedures, server process failure detection, and automatic server process restart. The design and implementation of fault‐tolerance support is optimized for high performance in the normal case (network connectivity provided by a high latency, low bandwidth, wireless link): measurements show a best‐case overhead of less than 7% for a reliable null RPC over wired and cellular dialup links. Experimental results from both micro‐benchmarks and applications, such as the Rover Web Browser proxy, show that support for reliable operation can be provided at an overhead of only a few percent of execution time during normal operation. This revised version was published online in June 2006 with corrections to the Cover Date.     

MTAODV:一种新的高速公路场景下VANET路由协议

在高速公路场景中,针对车辆间通信特性,在AODV的基础上提出了一种基于应用消息类型的改进路由协议(MTAODV).其核心思想是在路由建立过程中充分考虑VANET中应用消息的类型,从而减小路由请求洪泛范围,降低网络开销.仿真实验结果表明,与AODV协议相比,MTAODV协议能够有效地提高分组递交率,降低了路由开销,改善了分组时延和抖动.