Forwarding In Delay Tolerant Networks Research Articles

Application-based forwarding in Delay-Tolerant Networks

Delay-tolerant Networks (DTN) are wireless networks destined to serve places or functions with minimal or not well-established infrastructure. The DTNs are challenged by an intermittent connectivity between the adjacent nodes, and disconnections may occur due to power outages, technical issues or insufficient architecture. To address the transmitting phenomena of relatively large delays and error rates, an interest-based routing approach, in which different interests and data relay to each node will enhance the DTN capacity. The use of throw-boxes will increase the performance of the networks, and an efficient buffer management policy shall be administered to improve the performance of the network. In this paper, a hybrid buffer management policy is enacted in throw-boxes for increasing the performance and energy efficiency of the network. When the buffer becomes full, data with TTL less than 5 hours will be deleted first, and then the interest type with the most copies diffused or the more popular one in the network with a high hop count will be deleted from the throw-boxes so that the data would flow between nodes and other throw-boxes to reach the destination. Of course, the interest with less popularity can also reach the destination by utilizing this approach. Results show that the buffer management policy improves the performance of challenged networks by increasing the delivery probability, the overhead ratio and the delay are decreased and the average remaining energy has better performance compared to other routing protocols.

Distance-Based Energy-Efficient Opportunistic Broadcast Forwarding in Mobile Delay-Tolerant Networks

Mobile-relay-assisted forwarding in delay-tolerant networks (DTNs) can improve network capacity and packet delivery ratio but, at the same time, may significantly increase energy consumption at the system level. In this paper, we propose a distance-based energy-efficient opportunistic forwarding (DEEOF) framework for the broadcast transmission in mobile DTNs. DEEOF strikes a balance between energy consumption and network performance by maximizing the energy efficiency while maintaining a high packet delivery ratio. In the proposed algorithms, we define the metric of the forwarding equivalent energy efficiency distance (FEED) for broadcast transmission to quantify the transmission distances achieving the same energy efficiency at different time instances, or with different numbers of the relays in the source's transmission radius. Based on the concept of FEED, we propose two DEEOF algorithms for opportunistic broadcast forwarding, which makes the forwarding decision by comparing the current energy efficiency with the estimated future expectation and distribution, respectively. The performance improvement of the proposed DEEOF algorithms is also demonstrated by simulation, particularly for the cases in which the source has very limited battery reserves.

Congestion‐aware message forwarding in delay tolerant networks: a community perspective

SummaryIn delay tolerant networks, most of the existing message forwarding algorithms prefer to deliver messages to the nodes with a higher popularity or centrality in the hope of maximizing the delivery ratio or minimizing the end‐to‐end delay. This forwarding scheme is prone to cause unfair load distribution and further lead to network congestion, overlooked in the previous work. In this paper, we discuss the network congestion from a community perspective and take it into account the design of message forwarding algorithms. We first put forward a novel distributed community detection approach, which could track the evolution of communities. Based on the identified communities, we develop a congestion avoidance mechanism to divert the load away from the congested areas to the alternative custodians and further present a congestion‐aware message forwarding algorithm where messages can avoid being transmitted to the congested nodes. We finally evaluate the effectiveness of distributed community detection and congestion‐aware message forwarding through the extensive real‐trace driven simulations. Copyright © 2015 John Wiley & Sons, Ltd.

LAOF: location‐aware opportunistic forwarding scheme in mobile Ad hoc networks

AbstractDue to the high mobility of the nodes, the mobile ad hoc networks are expected to provide many opportunities for message forwarding in delay tolerant networks. Considering the typical mobility models, for example, the random waypoint (RWP) model and Manhattan model, we explore the probabilistic characteristics of the node contact provided by the mobile nodes. Following a progressive approach, we propose a location‐aware opportunistic forwarding scheme, which exploits the location information of the messages and the node mobility to conduct message forwarding. In order to provide a stable delivery ratio and avoid the extra network overhead, the message is forwarded to its destination regions or neighbor regions, which offer a better chance to reach the destination node. We construct a simulation environment, integrated with the RWP mobility trace and the Shanghai city taxis traces. Through extensive simulations, our scheme is demonstrated to outperform the best known opportunistic forwarding algorithms in terms of both delivery ratio/latency and transmission overhead. Copyright © 2014 John Wiley & Sons, Ltd.

Practical Bloom filter based epidemic forwarding and congestion control in DTNs: A comparative analysis

Epidemic forwarding has been proposed as a forwarding technique to achieve opportunistic communication in delay tolerant networks (DTNs). Even if this technique is well known and widely referred, one has to address several practical problems before using it. Unfortunately, while the literature on DTNs is full of new techniques, very little has been done in comparing them. In particular, while Bloom filters have been proposed to exchange information about the buffer content prior to sending information in order to avoid redundant retransmissions, up to our knowledge no real evaluation has been provided to study the tradeoffs that exist for using Bloom filters in practice. A second practical issue in DTNs is buffer management (resulting from finite buffers) and congestion control (resulting from greedy sources). This has also been the topic of several papers that had already uncovered the difficulty to acquire accurate information mandatory to regulate the data transmission rates and buffer space. In this paper, we fill this gap. We have been implementing a simulation of different proposed congestion control schemes for epidemic forwarding in ns-3 environment. We use this simulation to compare different proposed schemes and to uncover issues that remain in each one of them. Based on this analysis, we proposed some strategies for Bloom filter management based on windowing and describe implementation tradeoffs. Afterwards, we propose a back-pressure rate control as a well as an aging based buffer managing solution to deal with congestion control. By simulating our proposed mechanisms in ns-3 both with random-waypoint mobility and realistic mobility traces coming from San-Francisco taxicabs, we show that the proposed mechanisms alleviate the challenges of using epidemic forwarding in DTNs.

Optimal Forwarding in Delay-Tolerant Networks With Multiple Destinations

We study the tradeoff between delivery delay and energy consumption in a delay-tolerant network in which a message (or a file) has to be delivered to each of several destinations by epidemic relaying. In addition to the destinations, there are several other nodes in the network that can assist in relaying the message. We first assume that, at every instant, all the nodes know the number of relays carrying the message and the number of destinations that have received the message. We formulate the problem as a controlled continuous-time Markov chain and derive the optimal closed-loop control (i.e., forwarding policy). However, in practice, the intermittent connectivity in the network implies that the nodes may not have the required perfect knowledge of the system state. To address this issue, we obtain an ordinary differential equation (ODE) (i.e., a deterministic fluid) approximation for the optimally controlled Markov chain. This fluid approximation also yields an asymptotically optimal open-loop policy. Finally, we evaluate the performance of the deterministic policy over finite networks. Numerical results show that this policy performs close to the optimal closed-loop policy.

Optimal Joint Expected Delay Forwarding in Delay Tolerant Networks

Multicopy forwarding schemes have been employed in delay tolerant network (DTN) to improve the delivery delay and delivery rate. Much effort has been focused on reducing the routing cost while retaining high performance. This paper aims to provide an optimal joint expected delay forwarding (OJEDF) protocol which minimizes the expected delay while satisfying a certain constant on the number of forwardings per message. We propose a comprehensive forwarding metric called joint expected delay (JED) which is a function of remaining hop-count (or ticket) and residual lifetime. We use backward induction to calculate JED by modeling forwarding as an optimal stopping rule problem. We also present an extension to allow OJEDF to run in delay constrained scenarios. We implement OJEDF as well as several other protocols and perform trace-driven simulations. Simulation results confirm that OJEDF shows superiority in delay and cost with acceptable decrease of delivery rate.

BUBBLE Rap: Social-Based Forwarding in Delay-Tolerant Networks

The increasing penetration of smart devices with networking capability form novel networks. Such networks, also referred as pocket switched networks (PSNs), are intermittently connected and represent a paradigm shift of forwarding data in an ad hoc manner. The social structure and interaction of users of such devices dictate the performance of routing protocols in PSNs. To that end, social information is an essential metric for designing forwarding algorithms for such types of networks. Previous methods relied on building and updating routing tables to cope with dynamic network conditions. On the downside, it has been shown that such approaches end up being cost ineffective due to the partial capture of the transient network behavior. A more promising approach would be to capture the intrinsic characteristics of such networks and utilize them in the design of routing algorithms. In this paper, we exploit two social and structural metrics, namely centrality and community, using real human mobility traces. The contributions of this paper are two-fold. First, we design and evaluate BUBBLE, a novel social-based forwarding algorithm, that utilizes the aforementioned metrics to enhance delivery performance. Second, we empirically show that BUBBLE can substantially improve forwarding performance compared to a number of previously proposed algorithms including the benchmarking history-based PROPHET algorithm, and social-based forwarding SimBet algorithm.

Enhanced delegation forwarding in delay tolerant networks

Delay tolerant network (DTN) is a sparse wireless mobile network that does not guarantee a path between a source and a destination at any time. In DTN, one critical issue is to reliably deliver data with low latency. In an N-node network, naive forwarding approaches such as flooding and its derivatives make the routing cost very high (). Recently, an approach called delegation forwarding (DF) caught significant attention in the research community because it reduces the cost to while maintaining good performance. In this paper, we enhance the DF algorithm by proposing a probability delegation forwarding (PDF) that further reduces the cost to and a threshold-based probability delegation forwarding (TPDF) that closes the latency gap between DF and PDF. Simulation results show that both PDF and TPDF can achieve similar delivery ratio as DF at a lower cost if p is not too small.

Delegation Forwarding in Delay Tolerant Networks Multicasting (Invited Paper)

Delay tolerant networks (DTNs) are a special type of wireless mobile networks which may lack continuous network connectivity. Multicast supports the distribution of data to a group of users, a service needed for many potential DTNs applications. While multicasting in the Internet and mobile ad hoc networks has been studied extensively, due to the unique characteristic of frequent partitioning in DTNs, multicasting in DTNs is a considerably different and challenging problem. It not only requires new destinations of multicast semantics, but also brings new issues to the design of routing algorithms. In this paper, we propose new forwarding models for DTNs multicast and develop several multicast forwarding algorithms. We use delegation forwarding (DF) in DTNs multicast and compare it with single and multiple copy multicast models, which are also proposed in this paper. From the analytical results, we have the following conclusions: (1) Although the single copy model has the smallest number of forwardings, its latency is much longer than the other two models. (2) Among these three models, the delegation forwarding model has the least delay. The effectiveness of our approach is verified through extensive simulation both in synthetic and real traces.

Price: Hybrid geographic and co-based forwarding in delay-tolerant networks

Similarity-based techniques relying on contact patterns among nodes have shown to provide high delivery success rate when performing routing in delay-tolerant networks (DTN). Nevertheless, such approaches work well only when nodes exhibit high similarity values. In this paper, we propose Price (Periodicity-based Routing in Intermittently-Connected Environments), an agenda-based greedy forwarding scheme for DTNs that combines geographic-oriented forwarding with contact-based forwarding by relying packets according to predictable patterns of locations and contacts. We define the operation of Price and evaluate the performance of geographic forwarding under the framework of graph navigation to unveil a small-world phenomenon. We then gauge the performance of Price using a real-life mobility data set according to various well-known routing solutions such as Flooding, Prophet, Bubble Rap, and Wait. Simulation results show that Price largely outperforms other solutions, especially in terms of combined cost/delivery ratio.

Selective Message Forwarding in Delay Tolerant Networks

It is challenging to deliver messages in a network where no instant end-to-end path exists, so called delay-tolerant network (DTN). Node encounters are used for message forwarding. In this paper, we propose a DTN routing protocol SMART. SMART utilizes the travel companions of the destinations (i.e. nodes that frequently meet the destination) to increase the delivery opportunities while limiting message overhead to a bounded number. Our approach differs from related work in that it does not propagate node encounter history nor the delivery probabilities derived from the encounter history. In SMART, a message source injects a fixed number of message copies into the network to forward the message to a companion of the destination, which only forwards the message to a fixed number of the destination’s companions. Our analysis and simulation results show that SMART has a higher delivery ratio and a smaller delivery latency than the schemes that only use controlled opportunistically-forwarding mechanism and has a significantly smaller routing overhead than a pure flooding scheme.