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The Internet Engineering Task Force (IETF) has defined routing protocols for low power and lossy networks (RPL) for constrained devices. RPL constructs DODAGs (destination oriented directed acyclic graphs), to optimize routing. RPL ensures acyclic topology with the DODAG version number. However, the control message's DODAG version number is not authenticated. So, RPL is vulnerable to network resource attack known as DODAG Version Number (DVN) attack. DVN attack creates a packet delay, packet loss, cyclic topology, etc., in the network. This paper proposes a method for detecting DODAG version number attacks. Several existing schemes to defend against the DVN, such as cryptographic techniques, trust-based, threshold-based and mitigation are computationally intensive or require protocol modification. DVN does not change the packet format or sequence of packets, but can still perform attacks and hence fall under the category of stealthy attacks, which are difficult to detect using traditional intrusion detection system's (IDS). Discrete-event system (DES) based IDS have been applied in the literature for stealthy attacks that achieve low overhead, low false alarm rate, etc. However, the construction of DES-based IDS for network protocol may lead to errors, as modelling is manual. The resulting IDS, therefore, is unable to guarantee its correctness. This paper proposes linear temporal logic (LTL) based DES paradigm to detect DVN. LTL-based paradigm facilitates formal verification of the DES-based IDS, and hence the correctness of the scheme is ascertained. The proposed technique is simulated using the Contiki cooja simulator. When the percentage of spiteful nodes in the network increases, the true positive rate, and packet delivery rate drops, while the false positive rate and control message overhead increase. The memory requirement for sending the packets and verifying the nodes is minimal. The LTL-based IDS has been formally verified using NuSMV to ensure the correctness of the framework. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoT) implies a new model and concept in the world of information and communication technology that the non-cooperation of some nodes in providing services to other nodes may result in the disconnection of some things with each other. Consequently, the proximity of such nodes is considerably reduced the network performance. In this paper, a multiphase method based on game theory and direct and indirect reputation has been designed to stimulate selfish and malicious nodes to cooperate in the Internet of Things, which starts with setting up nodes in the IoT network. In the first phase, nodes are grouped in clusters with cluster heads to collect data. Then, they play a dynamic and multi-person game when they promote their own data packet or others' data packet in the second phase (multi-person game phase and data packet sending). The result of the game is applied to affect between nodes in the next phase. Nodes can pick their strategy when data packet forwarding in the third phase (direct and indirect reputation update). Nodes will update the neighboring node and the reputation table if they receive a confirmation message from the destination declaring that the data packet has a direct reputation. The results show that the accuracy of selfish node detection has increased by average of 8% and the false positive rate is 7% in comparison to comparative methods. [ABSTRACT FROM AUTHOR]

The lack of sufficient contact opportunities in sparse vehicular delay tolerant networks results in poor performance. The network performance can be enhanced by deploying additional small wireless devices called throwbox. Nonetheless, the deployment of throwboxes with distinct placement strategies results in diverse outcomes in terms of metrics such as delivery ratio (DR), delay, and overhead cost (OC). In this paper, the throwbox deployment problem has been presented as an optimization problem. A customized binary differential evolution (CBDE)-based iterative optimization method is employed to improve the DR. Furthermore, depending upon a specific application, it might be desired to have a balanced performance that optimizes the trade-off between different metrics. Therefore, the employment of a multi-objective CBDE (MOCBDE) technique is proposed to optimize the trade-off between DR and OC metrics. The proposed approaches are implemented using Matlab and opportunistic network environment simulator. The experimental results presented in the paper validates the superiority of the proposed CBDE approach over existing methods of throwbox deployment. In addition, the MOCBDE approach provides a set of non-dominated (also called pareto-optimal) solutions with an exhaustive view of desirable results. Consequently, depending on the application requirements, the method allows selecting suitable locations for throwbox deployment. [ABSTRACT FROM AUTHOR]

Mobile Ad-hoc Network (MANET) is one of the most important self-configuring and independent wireless network. Numerous intermediate nodes are used among MANET to interchange the information without the requirement of any centralized infrastructure. But some nodes act selfishly and utilize the resources only for their own purposes and do not share with the neighbors. This selfish nodes might delay or drop the packet and do not perform routing. Though watchdog is a well-known selfish node detection technique, it causes false negatives and false positives that can affect the performance in terms of precision and speed. To eliminate the drawbacks of existing approaches in selfish node detection, this paper integrates both Ad-hoc On-Demand Distance Vector (AODV) protocol incorporated with chimp optimization algorithm and Collaborative Contact based Watchdog to propose a novel technique called Chimp-CoCoWa-AODV in order to improve the performance of MANET. The main role of chimp optimization algorithm in AODV is to undergo optimal route selection process. The performance of the proposed Chimp-CoCoWa-AODV approach is compared with existing approaches in terms of average routing load, Average Packet Delivery Fraction (PDF), Average End-to-end Delay (EED), Average Throughput, Total packet drop in the application layer, and maliciously dropped packet in the routing layer. The simulation results shows that the proposed approach is effective with 82% PDF and 7.4 ms EED at 50 nodes in detection and isolation of selfish nodes in MANET even in the presence of malicious node. [ABSTRACT FROM AUTHOR]

Burst buffer has become a major component to meet the I/O performance requirement of HPC bursty traffic. This paper proposes Gfarm/BB that is a file system for a burst buffer efficiently exploiting node-local storage systems. Although node-local storages improve storage performance, they are only available during the job allocation. Gfarm/BB should have better access and metadata performance while it should be constructed on-demand before the job execution. To improve the read and write performance, it exploits the file descriptor passing and remote direct memory access (RDMA). It improves the metadata performance by omitting the persistency and the redundancy since it is a temporal file system. Using RDMA, writes and reads bandwidth are improved by 1.7x and 2.2x compared with IP over InfiniBand (IPoIB), respectively. It achieves 14 700 operations per second in the directory creation performance, which is 13.4x faster than the fully persistent and redundant case. The construction of Gfarm/BB takes 0.31 seconds using 2 nodes. IOR benchmark and ARGOT-IO application I/O benchmark show the scalable performance improvement by exploiting the locality of node-local storages. Compared with BeeOND, Gfarm/BB shows 2.6x and 2.4x better performance in IOR write and read benchmarks, respectively, and it shows 2.5x better performance in ARGOT-IO. [ABSTRACT FROM AUTHOR]

In predictable delay tolerant networks (PDTNs), the network topology is known a priori or can be predicted over time, such as space planet networks and vehicular networks based on public buses or trains. Due to the intermittent connectivity, network partitioning, and long delays in PDTNs, most of the researchers mainly focuses on routing and data access research. However, topology control can improve energy effectiveness and increase the communication capacity, thus how to maintain the dynamic topology of PDTNs becomes crucial. In this paper, a contact ability based topology control method for PDTNs is proposed. First, the contact ability is calculated using our contact ability calculation model, and then the PDTNs is modeled as an undirected weighted contact graph which includes spatial and contact ability information. The topology control problem is defined as constructing a minimum spanning tree (MST) that the contact ability of the MST is maximized. We propose two algorithms based on undirected weighted contact graph to solve the defined problem, and compare them with the latest method in terms of energy cost and contact ability. Extensive simulation experiments demonstrate that the proposed algorithms can guarantee data transmission effectively, and reduce the network energy consumption significantly. [ABSTRACT FROM AUTHOR]

As multi/many-core processors are widely deployed in high-performance computing systems, efficient intra-node communication becomes more important. Intra-node communication involves data copy operations to move messages from source to destination buffer. Researchers have tried to reduce the overhead of this copy operation, but the copy operation performed by CPU still wastes the CPU resources and even hinders overlapping between computation and communication. The copy engine is a hardware component that can move data between intra-node buffers without intervention of CPU. Thus, we can offload the copy operation performed by CPU onto the copy engine. In this paper, we aim at exploiting copy engines for MPI blocking collective communication, such as broadcast and gather operations. MPI is a messaging-based parallel programming model and provides point-to-point, collective, and one-sided communications. Research has been conducted to utilize the copy engine for MPI, but the support for collective communication has not yet been studied. We propose the asynchronism in blocking collective communication and the CE-CPU hybrid approach to utilize both copy engine and CPU for intra-node collective communication. The measurement results show that the proposed approach can reduce the overall execution time of a microbenchmark and a synthetic application that perform collective communication and computation up to 72% and 57%, respectively. [ABSTRACT FROM AUTHOR]

In recent years, WSNs are acquiring popularity due to small-sized and flexible implementation; many applications require quick data transfer with minimal energy consumption of nodes in the midst of the ubiquitous use of WSNs. These sensor nodes cover large regions according to application needs and choose the best optimal path. The main issue with WSN is how to cover the neighborhood correctly and send data to sink without falling into the trap of a single node and single route. Therefore, a recently researched approach namely the swarm-based dragonfly, which has been effectively used in miscellany applications is exploited for this work. The dragonfly method is based on the exploration phase using global search and exploitation phase using local search. The implicit swarming behaviors are thought to be the fundamental drive for routing algorithms. This paper introduce a Meta-heuristic based Optimized Opportunistic Routing Protocol for WSNs (MOORP) based upon the best optimal forwarder node selection and dragonfly route optimization. The forwarder node selection is optimized by residual energy and eucledian distance of the node. The path between forwarder and destination is identified by using the Dragon-fly algorithm. MOORP employs a route searching algorithm (RSA) and a Energy Level Matrix (ELM) update is used to enhancing the routing decision. The RSA finds an optimal path and selects the optimal forwarder node with the help of a heuristic update or ELM. MOORP performance is compared with other opportunistic routing protocols on important parameters such as the number of alive nodes, throughput, packet delivery ratio, message success rate, and average energy consumption,and also compare with pre-existing cluster based routing protocol. The simulation results show that the MOORP considerably outperforms its competitive techniques in terms of energy efficiency. [ABSTRACT FROM AUTHOR]

In this paper, network energy assesses the capacity of a node to convey messages to others. In most cases, network energy is created when two nodes interact with one another. If a node is part of the same network as the node it is connecting with, then it will be able to make an inter-network energy connection with the node it is meeting. In the case that this does not take place, there will be an accumulation of energy within the part of the network that is facing the node. A node with higher inter-network energy is considered suitable for forwarding. The energy optimisation is achieved using efficient identification of source and destination pairs. This work has considered two scenarios, i.e. lossless transmission and lossy transmission, for our experiments and evaluated the detection probability. The performance of the proposed PPM is evaluated in terms of delivery ratio, overhead and hops count performance measures. When the buffer size is set to 100 MB, PPM delivers 59% of messages with message overhead of 750 and it has a hop count of 2, which is comparable to the state-of-the-art methods. With lengthy lifetimes of IOT networks, PPM is capable of giving higher performance while maintaining the privacy of network. The detection probability for the lossy observations model is applied to a 10-node, 20-node, 30-node and 40-node IoT network. [ABSTRACT FROM AUTHOR]

Delay tolerant network solves technical challenges in the heterogeneous network that may lack end-to-end connectivity. However, due to the disconnected paths, message delivery is much dependent on the cooperation of intermediate nodes, but malicious nodes may inject other nodes with either bogus messages or copies of good messages. This causes relaying of unwanted packets, which in turn leads to draining the energy of the intermediate nodes. This scenario may be termed as flooding attack. The paper discusses three types of flooding attacks, namely breadth attack (type 1), breadth attack (type 2), and depth attack. Breadth attack (type 1) refers to attack by those malicious nodes that relay only bogus messages, breadth attack (type 2) refers to the attack by those malicious nodes that relay both bogus and good messages, and depth attack refers to the attack by those malicious nodes that create copies of its own good messages and floods in the network. In this paper, we present a novel reputation based schemas that detect the flooding type of malicious nodes in DTNs. We propose three algorithms where first algorithm Reputation Algorithm handles a breadth attack (type 1), second algorithm Reputation with Good Messages over Total Messages Algorithm handles both breadth attacks (type 1 and type 2), and third algorithm, Reputation using Good Messages over Total Messages with Check message Generation Rate (RepGMTMwithCGR) is robust for (depth attack + breadth attack) flooding attack. The simulation study shows RepGMTMwithCGR defends all categories of flooding attack considered in this paper and there is the improvement of 20% in message delivery, 61% decrease in relaying, 49% decrease in message dropping and 63% decrease in energy consumption in the presence of 30% malicious nodes in the network. The algorithm shows increase in message latency by 2% but decreases message latency by 25% when compared to existing work. The protocols can be employed in monitoring systems using base stations in open environments. [ABSTRACT FROM AUTHOR]

Delay Tolerant Network offers communication architecture for scenarios where attaining uninterrupted connectivity between source and destination is challenging due to dynamic topology, short transmission range, and mobility of nodes. The messages are delivered by a store, carry, and forward mechanism in which the node store the messages in its buffer, and carries them while moving and forward to its opportunistically connected peers. The buffer space is limited, and the stored messages are dropped to overcome congestion. The existing buffer management policies have utilized the message header data fields to compute heuristic metrics, or probability measures and have not focused on incorporating community characteristics in designing algorithms. In this paper, we have proposed a Social Community Buffer Management Policy for Delay Tolerant Networks in which the community metric consisting of Global Rank Value (GRV) and Local Rank Value (LRV) has been introduced. The GRV is the ability of any individual node to encounter the community in which the message destination resides. Similarly, LRV is the ability of a node to directly connect to the message destination. The congested node does not drop messages for which it has higher GRV and LRV values than predefined thresholds. Furthermore, we have integrated a message-locking mechanism in which the combination of lock variables such as Source Drop Lock, Must Accommodate Lock, Local Rank Lock, and Global Rank Lock are introduced within the message header. We have performed the simulation of existing BMSS, DOA, LIFO, MOFO, Ndrop, SHLI, and DLA with SCBM under real-time mobility scenarios. The simulation result proves the proposed SCBM performs better in terms of increasing delivery rate, buffer time average, and reducing overhead, message transmissions, and message drop. [ABSTRACT FROM AUTHOR]

Vehicular delay-tolerant networks follow a store–carry–forward mechanism to overcome the state of broken links between source and destination, which is crucial for autonomous vehicle networks. These networks depend upon the mobility of vehicular-relay nodes, which can adopt the store–carry–forward arrangement and provide consent to utilize their resources for packet forwarding. In reality, vehicular-relay nodes drop packets because of a lack of resources and selfish behavior, leading to potential failures in networks. The reason for this failure in performance is the absence of an efficient relay node selection strategy. Typically, vehicular delay networks can provide communication solutions in challenging conditions when other traditional networks fail to perform due to disconnection. However, if the routing strategy does not consider nodes' selfish nature and relay nodes' inefficiency, packet drops continue, and the approach will fail to perform. This paper proposes a routing strategy, known as the best-choice vehicular-relay selection strategy for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) transmission, to overcome this breakdown situation. The proposed strategy selects the best-performing vehicular-relay nodes and restricts the packet replication to low-performing vehicular nodes. The proposed routing strategy selects the best-choice relay nodes based on their past performance. Numerical analysis and our simulation results show that the proposed approach outperforms some of the leading routing strategies in its class by increasing the delivery probability, decreasing the overhead ratio, average latency, and the number of dropped packets in the vehicular network. [ABSTRACT FROM AUTHOR]

Delay Tolerant Network (DTN) establishes the communication framework in environments where source and destination cannot establish the end-to-end path due to the limited transmission range, frequent disconnections, and network partitioning. The messages are delivered to their destinations by adopting a store, carry and forward paradigm in which the node stores the arriving message in its buffer, carries it while moving, and forwards on connecting to other nodes. The DTN multi-copy protocols diffuse the several message copies on all connected nodes and deplete the network resources such as buffer space, bandwidth, and energy. This resource consumption is controlled by incorporating a social community message forwarding technique. The node employs the global rank forwarding metric while moving outside the community and shifts to the local rank forwarding metric while moving within the community. This method produces congestion in scenarios where the node continues message replications on higher global and local rank peers. As a result, more messages are dropped, and message delivery is reduced. This paper presented the Message Locking Routing Protocol for Delay Tolerant Network (CTML). The CTML controls the message forwarding process by employing the Local Rank Lock (LRL) and Global Rank Lock (GRL). The Local Rank Lock (LRL) controls the message transmission during node mobility within the community whereas Global Rank Lock (GRL) refrains the message forwarding during node mobility outside the community. Thus, the small number of transmissions reduces congestion. Similarly, CTML control message drop by using Message Drop Lock (MDL) where a node cannot drop a message with higher global rank or local rank values. Finally, the delivery ratio has been increased by using Deliver to Destine Lock (DDL) lock where a node with higher threshold values to meet the destination is enforced to forward the message directly to its destination. The simulation results prove that the proposed CTML has performed better in terms of reducing message transmissions , message drop, hop-count average, overhead, and raising delivery ratio. [ABSTRACT FROM AUTHOR]

With the recent endeavour of smart city mission, it is being planned to install sophisticated infrastructure for providing various smart services. But the planning to handle unwanted events like disaster has not received much attention as part of this endeavour. In a post-disaster scenario, one of the most important services is to disseminate crucial situational information among different stakeholders when the traditional communication infrastructure becomes non-functional. The smart phone based delay tolerant network (DTN) shows its useful applicability in such a scenario. Further, it is well established that due to the movement pattern of the stakeholders with handheld device, it typically forms clusters based on their work areas. However, the existing DTN routing protocols are not designed for cluster architecture. This motivates us to propose a cluster routing considering a utility based optimal dropbox (DB) deployment that assists in providing improved network performance. In this paper, we primarily consider that DBs are deployed at strategic locations of the disaster affected area using an existing utility based dropbox deployment. Then we propose a mixed integer linear programming based optimization model, to enumerate the optimal number of dropboxes to be deployed at high utility locations. We finally propose a cluster based routing with a target to improve network performance. We evaluate the comparative performance of our proposed optimal DB deployment based cluster routing through both theoretical analysis and simulation. Exhaustive simulation is carried out in ONE simulator using real disaster data. Results show our scheme's dominance over the competing schemes. [ABSTRACT FROM AUTHOR]

With the development and maturity of 5G communication technology, the intelligent terminals and applications in the Internet of Things have exploded. The large-capacity data generated by the Internet of Things has higher transmission requirements on the network. Opportunistic social networks use the "store-carry-forward" method to complete message delivery, so it is particularly important to select reliable relay users to ensure the integrity of data transmission. However, users have limited memory resources. A large number of redundant message copies in the network will lead to increased node energy consumption, which will further cause network congestion. In addition, the user's movement is random and dynamic. Frequent changes in the network topology may lead to transmission link interruption and data loss. Based on the characteristics of social networks, this paper proposes a clustered dataset transmission strategy in opportunistic social networks based on the probability of encounters between users and the characteristics of user motion (PC-OSN). First, the method divides users into different clusters according to the strength of the relationship between users, which effectively reduces the occupation of network resources when users are clustered. Then PC-OSN adopts different message forwarding judgment indicators within and between clusters. PC-OSN forwards messages in a cluster by using binary injection to ensure that messages are delivered to users with a high probability of encountering. The user's activity level and motion characteristics are considered comprehensively among the clusters to determine the user's priority so as to deliver the message to the reliable user. PC-OSN fully considers the characteristics of users and the correlation between users, reducing the blindness of message forwarding and waste of ineffective resources. Experimental results show that PC-OSN achieves a message delivery rate of 0.94, which is about 14% higher than other methods. Its average latency and network overhead are reduced by about 24% and 16%, respectively. [ABSTRACT FROM AUTHOR]

In a delay tolerant network (DTN) nodes are scattered and intermittently connected. In this network end-to-end path cannot be assumed to be available. Routing protocols in DTNs usually replicate message in the network to transmit the message toward its destination. Managing message replication and distribution, and finding appropriate relay nodes due to the lack of timely and precise information is a major challenge. Existing multi-copy routing protocols when replicate and distribute copies of message don't consider some capabilities of nodes as the power to take and carry copies, this may lead to delays in delivering the message. In this paper, we proposed a multi-step routing protocol for DTNs. In each routing step, our protocol first dynamically determines the needed number of copies and also share of nodes from these copies. It makes decisions with the help of an attribute named Replication Capability Rate (RCR). The fuzzy system provides RCR based on the capability of nodes as power and property of message as time to live. Then, protocol sprays copies until remaining single copy in the buffer of the node. Finally, the single copy of the message is exchanged between nodes according to the encounter frequency. Experiment results show that our protocol significantly decreases the average delay and keeps delivery probability high, in comparison with well-known protocols. [ABSTRACT FROM AUTHOR]

In the recent era, security is the major problem in sensor networks. Wireless sensor networks (WSNs) are mostly used for various real-world applications. However, WSNs face a lot of insider and outsider attacks, and it is complex to identify and protect towards insider attacks. Generally, an insider attack, in which the intruders choose several received data packets to drop, threatens the clustered WSNs. This situation has occurred because of the unattended clustered environments in the network. To overcome this problem, this paper proposes a trustable and secure routing scheme using two-stage security mechanism, and dual assurance scheme, for selecting the node and securing the data packet for WSNs. Both schemes are based on Active Trust to protect several kinds of attacks, such as black hole attack, and selective forwarding attack, during routing. Therefore, this paper identifies the trusted path and provides the secure routing paths using trust and Cuckoo search algorithm. Energy is the performance parameter utilized in the proposed scheme. The experimental result proves that proposed system provides the assurance to prolong the network lifespan and the probability of secure routing path in the network. [ABSTRACT FROM AUTHOR]

This paper presents a sparse ad hoc network where multiple mobility controlled message ferries cooperate to deliver messages for stationary and disconnected wireless nodes. Unmanned Aerial Vehicles (UAVs) are utilized as message ferries with an on-the-fly mobility decision making. The multi-hop delivery of messages is enabled by efficient message forwarding and replication among UAVs to accelerate the delivery of messages. Due to lack of global knowledge in UAVs, decisions in a UAV are made based on local observations. To this end, a signaling among UAVs occurs when they visit each other on-the-air. Through signaling, a UAV updates its view from the network and applies this information to its decision makers. Trajectory aware and priority based message replication schemes are proposed in this paper to limit the number of message replications and to decrease the delay of message delivery. The results show that the multi-hop delivery of messages in a message ferry network by message forwarding and replication among UAVs accelerates the delivery of messages comparing with a pure message ferrying scheme without any message forwarding. The proposed trajectory aware message replication scheme performs as good as the unlimited message replication scheme while decreasing the buffer length in UAVs. Moreover, the priority based message replication scheme in UAVs speeds up the delivery of high priority messages without any adverse impact on low priority messages. [ABSTRACT FROM AUTHOR]

A Delay Tolerant Network (DTN) is a network capable of handling long delays and data loss efficiently in various challenged scenarios and environments. Owing to the mentioned challenges, it becomes crucial to study how the routing protocols are designed to adapt in such networks. Currently, the research in this domain is focused on the improving the data delivery ratio and minimizing delays in the routing protocols. This paper reviews state-of-the-art routing protocols for Delay Tolerant Networks (DTNs) as well as performs their comparative analysis. DTN routing protocols are grouped into four categories viz encounter based, time based, infrastructure based and hybrid & others. This categorization depends on the information they use for relay selection routing. We have also discussed some of the inherent drawbacks such as energy consumption, delivery rates and buffer constraints of the existing routing algorithms. We have also conducted an empirical analysis and observed the performance of the most popular existing algorithms of encounter and time based category. This paper offers a widespread study of the routing protocols with their pros and cons. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the impact of delaying delay-tolerant calls under certain conditions in cellular networks. We propose to queue the call if the user agrees when the terminal has bad radio conditions and the system is loaded. The call is served as soon as radio conditions become good or the current load goes below a given threshold. We model the system as a continuous-time Markov chain, which allows us to compute the blocking probability, the mean waiting time and the mean service time. Numerical results show that when the proportion of users with delay tolerance is 20%, the system can bear 16% more calls with the same blocking probability, and 113% more calls if 80% of users are delay tolerant. [ABSTRACT FROM AUTHOR]

One of the major concerns in any emergency relief operation is appropriate allocation of scarce emergency relief materials to the affected community. Due to several reasons ranging from lack of mechanism to accurately assess demand and utility of relief materials to malicious participation of some of the stakeholders, such allocation may become ad-hoc. Thus, it becomes imperative to have an unchallengeable and globally accessible record of relief requirement vis-à-vis allocation for efficient relief management. Emergency response organizations (e.g. UNICEF) have recommended the adoption of blockchain technology to create such immutable records. However, the usage of blockchain is restricted by the availability of end-to-end internet connection which may not be available in a post-disaster scenario. This paper proposes ReliefChain, a blockchain leveraged post disaster relief allocation system over delay tolerant network that works in such environments. We validate relief requirements to mitigate resource diversion, forecasting the exact demand and enumerating precise utilities of relief items. We design smart contracts for creating new transactions to upload relief requirements and allocations in the blockchain network. The proposed system executes these smart contracts to create an immutable and globally accessible record of relief requirement and allocation. Effectiveness of the proposed system is evaluated through extensive simulation in Ethereum platform. Results substantiate the efficiency of the system over a system using baseline methodologies, in terms of design parameters like shelter specific deficit and average resource deficit while not compromising the blockchain performance in terms of processing time and gas consumption even in presence of malicious forwarders. [ABSTRACT FROM AUTHOR]

The vehicular delay-tolerant network is the real-life application based area of Delay tolerant network where communication takes place using vehicular nodes and roadside units. The topology used in vehicular networks is highly dynamic by architecture due to the use of moving vehicular nodes. It operates in such a scenario where a direct path between source and destination remains absent on the most piece of the time. In case of non-existence of connected path vehicular delay-tolerant network works opportunistically and uses the same store, carry, and forward paradigm as Delay Tolerant Network. However, the routing protocols designed for vehicular delay-tolerant network faces crucial challenges like inadequate relay node, incomplete data transfer, a large number of packet drop, and uncertain delivery time. In this research paper, we propose a novel routing strategy for the vehicular delay-tolerant network. The proposed routing strategy selects efficient vehicular relay node for complete packet transfer and intelligently reduces the packet drop for timely packet delivery. We implement the proposed routing strategy in the ONE simulator; the ONE simulator provides an opportunistic environment for nodes. We analyze the performance of the proposed strategy under various simulations results using different parameters. The results show that the proposed strategy outperforms standard routing protocols in terms of considered parameters and provide an efficient solution for the problem of disconnection. [ABSTRACT FROM AUTHOR]

A delay-tolerant network (DTN) is a network with dynamic topology changes, network partitions and node mobility. Multi-copy routing protocols are usually adopted to overcome these characteristics. Although multi-copy routing protocols can improve the message delivery ratio and reduce the message propagation delay, they also easily exhaust the limited storage space of nodes, resulting in buffer overflows. The major task of buffer management is to determine which message will be discarded when buffer overflows happen. Determining the order of discarding messages will directly affect the performance of the network. In this paper, we propose a novel weight-based buffer management policy (NWBBMP) that divides messages in the node into a priority message queue, a high-weight message queue and a low-weight message queue. When a node receives a new message that causes a buffer overflow, the algorithm determines which queue’s messages will be discarded according to whether the current node is the destination node of the new message. Simulation results show that our algorithm outperforms traditional buffer management algorithms in terms of delivery ratio, average delay and network overhead. [ABSTRACT FROM AUTHOR]

Delay Tolerant Networks (DTNs) have attracted various interests these days. Since DTNs are subject to high loss rate, large delay, intermittent connection, and even no end-to-end connectivity, relay nodes, such as throwboxes, are deployed to enhance network performance. Internet-based systems have contemporaneous connectivity between location-distributed nodes, and this does not apply to DTNs. Thus, the traditional relay node deployment strategies are no longer suitable for DTNs. In this paper, we propose a novel strategy, named Connection-2 (CO2), to deploy throwboxes to enhance the fault tolerance of DTNs. CO2 constructs a 2-connected DTN using an approximation algorithm. Every mobile node in the 2-connected DTN can reach another mobile node via two or more node-disjoint paths within its mobility range. While enhancing fault tolerance, the number of throwboxes that CO2 requires is small. We conduct various experiments based on the simulation of the real Tuscaloosa bus transit system and compare its performance with two popular strategies. Experimental results show that CO2 is effective. [ABSTRACT FROM AUTHOR]

The IPv6 routing protocol for low-power and lossy networks (RPL) is the standard routing protocol for IPv6 based low-power wireless personal area networks (6LoWPANs). In RPL protocol, DODAG information object (DIO) messages are used to disseminate routing information to other nodes in the network. A malicious node may eavesdrop DIO messages of its neighbor nodes and later replay the captured DIO many times with fixed intervals. In this paper, we present and investigate one of the severe attacks named as a non-spoofed copycat attack, a type of replay based DoS attack against RPL protocol. It is shown that the non-spoofed copycat attack increases the average end-to-end delay (AE2ED) and packet delivery ratio of the network. Thus, to address this problem, an intrusion detection system (IDS) named CoSec-RPL is proposed in this paper. The attack detection logic of CoSec-RPL is primarily based on the idea of outlier detection (OD). CoSec-RPL significantly mitigates the effects of the non-spoofed copycat attack on the network's performance. The effectiveness of the proposed IDS is compared with the standard RPL protocol. The experimental results indicate that CoSec-RPL detects and mitigates non-spoofed copycat attack efficiently in both static and mobile network scenarios without adding any significant overhead to the nodes. To the best of our knowledge, CoSec-RPL is the first RPL specific IDS that utilizes OD for intrusion detection in 6LoWPANs. [ABSTRACT FROM AUTHOR]

With the development of vehicle communication technologies, Vehicular Ad Hoc Networks (VANETs) through short distance communication technology achieve communication in Vehicle to Vehicular (V2V) and Vehicular to Infrastructure (V2I), which provides the basis for the implementation of application. However, the privacy and security of vehicle and message forwarding are vulnerably attacked by attacker due to the dynamic network topology. To address the problems, a Socially Aware Security Message Forwarding Mechanism (SASMF) based on trust assessment is proposed in this paper. Firstly, the pseudonym is used to protect the privacy of the vehicles, and the exchange entropy is as a measure to evaluate the exchange conditions of the pseudonym to avoid the continuous tracking of the vehicle by the attacker. Furthermore, according to the trust gradient, the message is forwarded in the form of multiple pieces of information to several relay vehicles and to the Application Provider (AP) through the Road Side Units (RSUs). Results show that the proposed mechanism can effectively improve the success rate of message forwarding and reduce the risk of message leakage and better protect the privacy of VANETs. [ABSTRACT FROM AUTHOR]

Routing and secure communication are important concerns in Delay Tolerant Networks (DTNs). Previously designed security schemes utilize traditional public key cryptosystems for entity and data security that provide security under some hard problems like integer factorization and discrete logarithmic problems. These algorithms are vulnerable to Quantum attacks. In this paper lattice based cryptosystem has been used first time for DTN security. Lattice based cryptosystems utilize post-quantum cryptographic algorithms which are unbreakable by quantum attacks. First we present a novel Hierarchical structure for DTN having intracluster and intercluster communications. Then, we propose a security design to provide end-to-end security to DTN application data using lattice based cryptographic signature and encryption algorithms, secure under LWE hard problem over lattices. For securing intracluster and intercluster communication, three new schemes have been proposed: (i) Lattice based hierarchical identity-based key agreement scheme, based on lattice based Diffie-Hellman key agreement protocol, secure under LWE assumption but adapted to hierarchical structure. (ii) To derive new session keys, i.e. keys for new joining nodes and for key refreshment, a new lattice based hierarchical identity-based key update scheme has been proposed, which is based on Singh et al.'s lattice based forward secure identity-based encryption algorithm, (iii) A lattice based non-interactive key agreement scheme, based on schemes proposed by Agrawal et al. and Singh et al., has been proposed for generating a secret key for two communicating nodes in different clusters. This design can effectively resist man-in-the-middle attack, replay attack, dictionary attack, and parallel session attack and maintains forward and backward secrecy. [ABSTRACT FROM AUTHOR]

Data delivery in Cyber-Physical Battlefield Perception Systems(CPBPS) is a challenging task due to the ubiquity locations and the high mobility of node. Due to the special geographical circumstances, communication networks based on fixed infrastructure are unlikely to be established. This paper presents an air-ground coordination communication transmission network, which consists of Unmanned Aerial Vehicle (UAV) subnets and ground vehicle subnets. The UAVs exploit air-to-air (A2A) and air-to-ground (A2G) communication links to assist vehicle communications. However, overreliance on satellite positioning may cause military information to leak. Therefore, we proposed a K-Nearest Neighbor (KNN)combined with genetic algorithms and based on machine learning system (MLS) for data delivery for battlefield environment to realize the privacy protection and guarantee the security with better prediction. The proposed KNN machine learning system can estimate the movement and path of vehicles based on the mobile information obtained. Furthermore, in order to transmit data of UAVs more efficiently, the genetic algorithms (GA) is utilized to determine the relative location of UAVs. Simulation results verify the performance of proposed algorithm. [ABSTRACT FROM AUTHOR]

In traditional Mobile Adhoc Networks routing algorithms, the existence of a sustainable path between the source and destination is a crucial issue. These algorithms are shown to be unsuccessful in Delay Tolerant Networks (DTNs) since the network is almost disrupted, and then such a path is not guaranteed. Although Store-and-Forward routing approach has provided an adequate solution for these networks, it suffers from the large end-to-end delay and the additional traffic and communication costs incurring the network. This study presents an efficient single-copy home-based routing scheme for DTNs. Two different scenarios, referred as blind and semi-blind, are considered based on the amount of available knowledge about the destination. Simulation results presented in this paper demonstrate that the performance of the proposed scheme is closely approaching the unrestricted flooding algorithm, the Epidemic. Moreover, the proposed scheme provides a low communication cost, an outstanding end-to-end delay and a high successful delivery ratio as compared to state-of-art algorithms. [ABSTRACT FROM AUTHOR]

Mobile social networks are a type of delay tolerant network consists of a large number of mobile nodes with social characteristics. The pattern of data transmission and delivery across these networks is due to intermittent, storage, transport and forward connections. Therefore, relay nodes play an important role in these networks. One of the problems with these networks is that there is selfishness in relay nodes. Many algorithms have been proposed to detect and counteract these selfish nodes, but these methods have low detection rates. This paper presents an algorithm for finding selfish nodes and how to persuade them to collaborate based on the game theory. The simulation results show that the proposed method improved the correct detection rate compared to the other methods. First, it applies the Nash equilibrium to identify the selfish nodes and then using the credentials in the relay phase, it forces the selfish nodes to cooperate. The parameters and how the nodes are applied will increase the learning power of the system. The governing rules are applied to the inference system after the learning process. According to the results obtained at the datacenter of the Tabriz University, the improvement has been dramatic, with more than 98% of packets being transferred to the destination in due time and less than 2% of the them has been deleted from the network or their time to live was over. We tried to use the closest nodes to the destination with highest remaining energy to send the data. [ABSTRACT FROM AUTHOR]

Nowadays, vehicles have been equipped with various kinds of sensors which produce so called big data constantly. Among them, multimedia contents form the major part of the total generated data. They are usually shared among vehicles in a region of interest with less concerns on delay criteria. Therefore, to reduce cost, these data will be delivered using a carry-and-forward method in a Vehicular Delay Tolerant Network. Since the volume of these data is not negligible, not only delivery utility but also memory space usage must be considered while designing forwarding strategy. ThrowBoxes have been utilized to increase encountering opportunities. In this paper, we develop an optimal data packet assignment algorithms to achieve global maximum delivery utilities among ThrowBoxes. We evaluate the proposed scheme with the real world data trace. The results show that our scheme achieves better performance in terms of delay, delivery ratio, cost and other metrics. [ABSTRACT FROM AUTHOR]

At a time when the Delay Tolerant Network (DTN) Research Group is making great strides in establishing the much anticipated Solar System Internet (SSI) in space, its terrestrial counterpart is not far behind. The Earth bound DTN has been dedicated to connecting remote, heterogeneous, fluctuating, mobile and undisciplined networks like sensor, military and disaster struck areas. The Homing Pigeon Based DTN (HoP-DTN), a variant of DTN, was specifically conceptualized to serve some of these networks whose characteristics are different from the general delay or disruption tolerant networks. HoP-DTN uses special message carrying nodes, pigeons, to proactively route messages around the network. As it works in areas like disaster response or military, energy conservation is imperative here. Till now providing a solution to this energy issue has been lacking in HoP-DTN. Also routing in HoP-DTN is a Traveling Salesman Problem. This paper proposes a 4-step mechanism to address both of these issues. In view of that some changes to the classical modeling of HoP-DTN has been done to accommodate the variations. The deployment area has been divided into zones with pigeons following a 4-step detailed course plan and scheduling strategy to achieve better routing and more energy efficiency. To further enhance energy efficiency we introduce a Blockchain inspired energy sharing scheme. Mathematical modeling and simulation results further affirm our proposition. [ABSTRACT FROM AUTHOR]

This paper evaluates the performance of a wireless powered communications system, where an energy-aware relay can ability of controlling proper energy harvesting parameters for obtaining maximal throughput. Considering a power splitting approach, the relay first can calculate percentage of harvested wireless energy from power supply source, and then transmits information to the destination. This paper proposes the dynamic harvesting power allocation policy for energy harvesting and analytical expressions for the delay-limited and delay-tolerant throughput related to amplify-and-forward relaying mode. In particular, the optimal power coefficients can be derived in closed-form expressions, in which the maximal throughput can be obtained in special case, i.e., high transmit power regime. In addition, the impact of transmit power, power splitting fraction, the fixed rate factors, noise levels are well studied. Simulation results validate the theoretical expressions and show the effectiveness of the proposed policy. [ABSTRACT FROM AUTHOR]

MANETs are self-configured network. Nodes in Manets need not follow a specific infrastructure. Nodes are connected wirelessly and so nodes can travel to any direction. Manets assure that all its nodes are cooperating with each other. Sometimes, some nodes may not be reliable. These unreliable intermediate nodes participate in the packet forwarding and drop the packets instead of forwarding them to the destination node. This type of security attack is called black hole attack (Baadache and Belmehdi in Int Comput Sci Inf Sec 7(1):1–10, 2010). In this paper, an efficient method of route discovery process is used which bypasses the black hole nodes and uses only the reliable route for transmission. The main advantage of using the proposed method is that there is no need to maintain black hole list. So, there is no need to check the black hole list each time during route discovery. Dynamic source routing (DSR) is used for the transmission of packets. The simulations are done to measure packet delivery ratio, packet drop, average throughput, normalized routing overhead and average end-to-end delay. Simulation results shows that the proposed method improves the packet delivery ratio in presence of black hole and reduces the packet drop. Also the communication overhead is reduced which in turn minimizes the resource utilization in Manets. [ABSTRACT FROM AUTHOR]

Opportunistic routing is a promising routing paradigm which increases the network throughput. It forces the sender's neighbors, who successfully overheard the transmitted packet, to participate in the packet forwarding process as intermediate forwarding nodes. As a seminal opportunistic routing protocol, MORE combines network coding idea with opportunistic routing to eliminate the need for strict coordination among active forwarding nodes. In this paper, we show that MORE performance does not scale well with the route length, especially when the route length goes beyond two hops. Also, we found that MORE fails to establish a working opportunistic route in sparse networks. Clearly, the network throughput is directly influenced by both the quantity and quality of forwarding nodes, and their cooperation order. In this paper, we propose a new forwarder selection mechanism which considers the route length, link qualities, the distance from the source, and nodes density. It eliminates the occasional route disconnectivity happening in MORE and improves the quality of the established opportunistic routes. The simulation result indicates that our proposal always outperforms MORE when dealing with long opportunistic routes. [ABSTRACT FROM AUTHOR]

The problem of yield estimation and optimization of analog circuits is addressed in this paper. Given convex design-space constraints that define the feasible region for the design, we first linearize the feasible region by approximating it with linear constraints. Using the linear constraints approximating the feasible region, we make primarily two contributions in this paper—first we use the concept of parameter importance, introduced in Naidu (20th International conference on VLSI design, 2007. Held jointly with 6th international conference on embedded systems. IEEE, pp 265-270, 2007) and expanded on in Kondamadugula and Naidu (ACM Great Lakes symposium on VLSI. IEEE, pp 452-457, 2016), to partition the design space variables into those that affect yield a lot, and those that have only a marginal impact, and then use this information to speed-up a Monte-Carlo method that searches for a high-yield design point. Specifically, a two-step sampling procedure is devised for the variables where the outer-most loop is dedicated to the "weak" variables while the inner loop is dedicated to the "strong" variables. Thus the given simulation budget is then disproportionately directed towards those design space parameters deemed more important. Since there are likely be only a few variables that impact yield greatly, we can choose to use low-dimensional quasi-Monte-Carlo sequences for sampling in the inner loop which is an added benefit of our technique. For each sample design point, the Monte-Carlo algorithm would need to calculate yield using the Cadence yield estimation tool. This is a costly procedure. For the second application of the concept of parameter importance, we propose a fast procedure for calculating yield that works with a linear approximation of the feasible region, and uses design space information to speed up the calculation of yield. We compare our methodology with the standard one using the Cadence circuit simulator environment in 180 nm technology and show that we obtain superior results in the same amount of simulation time. [ABSTRACT FROM AUTHOR]

Delay tolerant networks are among mobile ad hoc networks. There is not a complete and connected route between the source and destination in these networks due to the dispersion of the nodes and inconsistency of the links between the nodes every moment. Therefore, store-carry and forward patterns is used to send the data. If the source node encounters the destination node, it delivers the message to the destination or else it waits for an appropriate opportunity. The previous algorithms such as Fuzzy Spray, APRP, AFRON, AFSn, and Enhanced Fuzzy logic-based Spray and wait have used fuzzy logic to manage buffer. It seems that using fuzzy logic to determine the relay node can increase the efficacy of these networks. In this paper to determine the relay node we have used fuzzy logic. The fuzzy system inputs are buffer capacity parameters, remaining energy, and the number of node encountering. The output of fuzzy system can be one of the states of do nothing (don't send), spray relay, direct transmission and carrier node. The simulation results showed that the proposed method has had improved the similar methods regarding the hop count and the delivery ratio. [ABSTRACT FROM AUTHOR]

Delay tolerant network is a type of network where the end-to-end path is not available from source to destination due to the node mobility, dynamic topology and network partitioning or such a path is highly unstable and may split almost immediately after it has been explored. In this background, existing ad hoc routing protocols would be unsuccessful. Therefore, the concept of store-carry-forward mechanism is utilized by introducing a new layer on the top of transport layer called as bundle layer. The bundle layer store message(s) in a finite size buffer for the long duration of time. As a result, node buffer runs out of space and drop messages to overcome congestion. In this paper, we aim to schedule the node buffer by using local knowledge-based buffer management policies called as best message-size selections buffer management policy. We have utilized the local information available in message header such as message-size to control the drop of messages. The evaluation of proposed policy with the existing DOA, DLA, LIFO, MOFO, N-drop and SHLI have been analyzed in ONE simulator in terms of reducing message drop, overhead, latency and raising the delivery ratio. [ABSTRACT FROM AUTHOR]

In this paper, we propose an energy-saving video compression scheme targeting to work over an IoT network where the perception layer is implemented through smartphone-based delay-tolerant network (DTN). Here, the inter-frame compression is done by a proposed progression-based frame prediction technique and a newly introduced frame-similarity measurement parameter. The inter-frame co-relation is removed by using progression method followed by identifying similarity of the frames selected by the progression method. On the other hand, the intra-frame compression is done by adopting an existing compression technique with suitable modification to make it more energy saving over its existing counterpart. Once the compressed video is transmitted over the IoT network, at the server side it is reconstructed where we use the service of a popular online face recognition API, KAIROS considering an application of disaster victim recognition. The comparative performance of the scheme is evaluated both theoretically and through ONE simulator-based simulation. Precisely, we claim that our scheme saves on average 71.46% energy over its competitors with least memory usage and acceptable reconstruction quality. Finally, the entire scheme is evaluated through testbed implementation and shown that it can recognize faces successfully from the videos transmitted over DTN-based IoT with accuracy more than 0.96 while keeping compression ratio at more than 31. [ABSTRACT FROM AUTHOR]

Delay Tolerant Networks are a type of challenging, uninterrupted network in which there is not an end-to-end path between the source and the destination. These networks play a key role in managing crises in natural disasters such as earthquakes, fires, floods, and more. Due to limited resources, nodes may be reluctant to cooperate in the message relaying and may behave selfishly. Eventually, this lack of cooperation can result in performance degradation. Game theory is one of the mathematical tools to motivate the intermediate nodes to forward messages. In this paper, we use the theory of auction between relay nodes to motivate them to collaborate in forwarding messages. Based on the second-price sealed-bid auction mechanism, the node that does not cooperate in forwarding messages fails to acquire utility. In this way, if the node itself intends to send a message to another node, it will not be able to do so due to a lack of budget. Thus, the selfish behavior of the node causes it to be harmed. Our simulations using the ONE simulator shows that the performance of the proposed method in moderate traffic is improved in terms of significant criteria such as delivery ratio, average buffer usage, hop count, overhead, and so on. The results also show that under intense traffic conditions, the performance of the proposed method is far better than that of moderate traffic. [ABSTRACT FROM AUTHOR]

In vehicular ad-hoc network, vehicles are move very speedy thus their topology is changing frequently and intermittent connectivity occur often. The intermittent connectivity network (delay and disruption-tolerant network) resulting is end to end path is absent. In this intermittent network connectivity areas, during emergency event occurs, emergency rescue message (Example: Fire, Accident, etc.,) are sent to a rescue team is most necessary. Due to these constraints, general ad hoc protocol approaches is not suitable and, as a result, alternative protocol must be deliberated. This leads to the make a specific protocol mechanisms able to deliver both fast and trustworthiness in-order delivery emergency message needed. Thus we introduce the DFEMDR protocol, it follow the vehicular delay tolerant network (VDTN) common technique store carry-forward method and message replicas. This paper describes an efficient Delay tolerant Fast Emergency Message Dissemination Routing Protocol, called DFEMD routing protocol. This protocol enables in VDTN, the source node broadcast an emergency message to all available node in its communication range. The source node allocates a message replicas and message time to live to the neighbour nodes (forwarded node) based on that node has credence value. Credence value is calculated to all nodes based on two values; the first value is visited level estimation, it is calculated based on the number of nodes previously visited by the node. The second value is Destination Reaches Level Estimation (DLE); it is calculated based on the number of times the node successfully delivered the message to the destination. Finally, each node credence value is calculated, from this visited level and destination reaches level estimation values. Finally, the trust authority received emergency messages and evaluate the trustworthiness of message based on message reputation value or message confidence value. [ABSTRACT FROM AUTHOR]

In the era of modern technology, the demand for seamless and fast communication service is gradually increasing. Moreover, as time goes on, more devices are getting connected to the network. In the vast network, for quick responses to these devices, the delay becomes one of the important factors to concern about. Among different types, Queuing delay causes more impact on a network compared to other delays. A survey on delay, different models, effects, and management are illustrated here. Queuing models, like Little Theorem, M/M/1, M/M/m, M/G/1, etc, are discussed in detail. We move on explaining the delay effects on different types of the network such as Wireless network, Mobile communication network, SDN, IoT, etc. This paper also focuses on TCP/IP fields like ECN bits, MPLS, and characteristics of flows. Lastly, the effects of delay on other related networking are discussed. [ABSTRACT FROM AUTHOR]

Intermittently connected mobile networks (ICMNs) serve as an important network model for many critical applications. This paper focuses on a continuous ICMN model where the pair-wise contact process between network nodes follows a homogeneous and independent Poisson process. This ICMN model is known to serve as a good approximation to a class of important ICMNs with mobility models like random waypoint and random direction, so it is widely adopted in the performance study of ICMNs. This paper studies the throughput capacity and delay-throughput tradeoff in the considered ICMNs with Poisson contact process. For the concerned ICMN, we first derive an exact expression of its throughput capacity based on the pairwise contact rate therein and analyze the expected end-to-end packet delay under a routing algorithm that can achieve the throughput capacity. We then explore the inherent tradeoff between delay and throughput and establish a necessary condition for such tradeoff that holds under any routing algorithm in the ICMN. To illustrate the applicability of the theoretical results, case studies are further conducted for the random waypoint and random direction mobility models. Finally, simulation and numerical results are provided to verify our theoretical capacity/delay results and to illustrate our findings. [ABSTRACT FROM AUTHOR]

Vehicular delay tolerant networks (VDTNs) present an efficient platform for delivering delay tolerant contents in vehicular networks by utilizing vehicle to vehicle or vehicle to road side infrastructure communications. Routing protocols play an essential role in VDTNs environment to provide high routing performance. However, most of existing vehicular network routing methods suffer from scalability issues and cannot make a trade-off between different performance criteria. In this paper we introduce an innovative hierarchical VDTNs scheme, called Hierarchical and Intelligent Vehicular Delay Tolerant Content Routing (HI-VDTCR), to establish a scalable delivery routing mechanism and provide a balance between different performance criteria. HI-VDTCR consists of two layers. An upper layer is responsible for sending messages to the destination vicinities without imposing high overhead to the network and a lower layer is tasked with delivering messages to the destination node by introducing a Markov decision process model, as an efficient reinforcement learning algorithm, for forwarding messages to the destination rendezvous. The proposed hierarchical and intelligent design empowers HI-VDTCR to provide an acceptable scalability in terms of network operation area and number of vehicle nodes. Evaluation results confirm that HI-VDTCR method outperforms other well-known vehicular routing methods. [ABSTRACT FROM AUTHOR]

In recent years, more and more people begin to focus on data delivery through opportunistic contacts among mobile users. In most cases, the data that we expect to share with others are videos, such as popular music videos and funny films. Because the video delivery will consume numerous resources of devices, few people will provide such service for others without any benefit. Thus, this paper centers on the incentive mechanism design for video delivery in opportunistic networks. Although several incentive schemes for such kind of networks have been proposed, however, they all mainly focus on the encouragement of general data forwarding, and almost none of them aims to stimulate nodes to realize the performance objective of networks. In this paper, we propose Videocent, a novel quality-oriented incentive mechanism for video delivery, which takes the characteristics of video data into account and formulates the video delivery among nodes as a game. This mechanism could not only encourage nodes to participate in the video delivery but also stimulate them to follow the defined rules to optimize the video delivery quality of whole networks. Its performance is validated through extensive simulations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Multicasting for delay-tolerant networks (DTNs) in sparse social network scenarios is a challenge due to the deficiency of end-to-end paths. In social network scenarios, the behaviors of their nodes are controlled by human beings, and node mobility is the same as that of humans. To design the multicasting algorithms for DTNs, therefore, it would be promising to capture the intrinsic characteristics of relationships among these nodes. In this paper, multicasting in DTNs is regarded as a message dissemination issue in social networks, and an egocentric network focused community aware multicast routing algorithm (ENCAR) is proposed. As distinct from some social-based routing algorithms which only focus on centrality analysis, ENCAR is an utility based and hierarchical routing algorithm, its utility function is constructed on the basis of centrality analysis and destination-oriented contact probability. We take notice of clustering phenomenon in social networks, and present the community aware forwarding schemes. In addition, to simulate the mobility of individuals in social networks, a novel community based random way point mobility model is also presented. In this paper, the performance of ENCAR is theoretically analyzed and further evaluated on simulator ONE. Simulation results show that ENCAR outperforms most of the existing multicast routing algorithms in routing overhead, on condition that delivery ratio is relatively high, with other significant parameters guaranteed to perform well. [ABSTRACT FROM AUTHOR]

We propose a suppressive fair buffer management policy for intermittently connected mobile ad-hoc networks. So far, several buffer management policies have been considered. These existing buffer management policies assume that all stored messages can be replaced when nodes encounter each other. Buffer management policies, however, can prioritize messages stored at the receiving side over those at the sending side. By doing this, message transmissions are suppressive, and thus energy consumption in terms of sending messages is reduced. Moreover, our proposed policy gives relay messages with a small number of message copies to high priority. Specifically, our proposed policy maintains a sharing of buffer spaces that is as fair as possible. In this paper, we reveal how the suppression of receiving messages affects the system performance compared with existing buffer management policies. Through simulation experiments, we show that the suppressive fair buffer management policy improves energy consumption without largely degrading the delivery failure probability and the mean delivery delay. [ABSTRACT FROM AUTHOR]