A survey of routing algorithms in Delay Tolerant Networks

The underwater acoustic channel features long and variable propagation delay, high bit error rate and limited bandwidth. Moreover, underwater mobile networks consisting of Autonomous Underwater Vehicles (AUVs) for surveillance and monitoring applications often suffer from intermittent connectivity as nodes move around the area of operations. Therefore, this scenario is appropriately modeled as a Delay-Tolerant Network (DTN). In this paper, we investigate two classes of DTN routing protocols: Spray-and-Wait (SNW) and the Resource Allocation Protocol for Intentional DTN (RAPID), together with a standard flooding protocol for underwater mobile networks, and their performance is analyzed in terms of packet delivery ratio, average end-to-end delivery delay and throughput, in different load conditions across various node mobility scenarios. Our results show that RAPID performs better than other DTN routing protocols in terms of packet delivery ratio at higher load conditions irrespective of node mobility, whereas the Binary version of SNW has the best performance in terms of average delivery delay.

Many Internet of Things (IoT) applications have been developed and implemented on unreliable wireless networks like the delay tolerant network (DTN); however, efficient data transfer in DTN is still an important issue for the IoT applications. One of the application areas of DTN is vehicular delay tolerant network (VDTN) where the network faces communication disruption due to lack of end‐to‐end relay route. It is challenging as some of the nodes show selfish behavior to preserve their resources like memory and energy and become noncooperative. In this article, an honesty‐based democratic scheme (HBDS) is introduced where vehicles with higher honesty level are elected as heads—during the process. Vehicles involved in the process would maximize their rewards (reputation) through active participation in the network activities, whereas vehicles with noncooperative selfish behavior are punished. The honesty level of the heads is analyzed using Vickrey, Clarke, and Groves (VCG) model. The mathematical model and algorithms developed in the proposed HBDS technique are simulated using the VDTNSim framework to evaluate their efficiency. The performance results show that the proposed scheme dominates current schemes in terms of packet delivery probability, packet delivery delay, number of packets drop, and overhead ratio.

In this paper, we study the application of Linear Network Coding to routing in sparse networks, where the average number of neighbors of a node is less than one. Routing in such networks is facilitated by mobility of the nodes, which create sporadic connections in the network. Due to the long end-to-end packet delivery delays, such networks can support only Delay Tolerant applications. Techniques such as Epidemic Routing are then used to reduce the packet delivery delay. However, when the nodes are equipped with limited storage, the effectiveness of Epidemic Routing partially vanishes and the reliability of packet delivery is reduced. We show that through the use of Linear Network Coding, the probability of packet delivery can be improved for certain region of the network operation. We derive a mathematical model for the condition of this improvement and we confirm our results through simulations.

A taxonomy on misbehaving nodes in delay tolerant networks

Disjoint multipath routing is an attractive approach for improving the reliability of data delivery in wireless sensor networks. Recently, the issue for maintaining the robustness and efficiency of the disjoint multipath routing against network failures such as network holes are being studied. Several protocols have been proposed to handle the network failures. However, they cause the large performance degradation on data delivery ratio and delay due to its centralized manner for detouring the network holes in irregular network environments. Thus, we propose a Localized Disjoint Multipath Routing protocol called LDMR which can achieve reliable data delivery ratio and stable data delivery delay while handling network failures. LDMR constructs the fully disjoint multipath and manages them by using a localized management method with a path priority rule. Simulation results show that our protocol provides the more stable and reliable performance than the previous protocols in terms of packet delivery ratio and packet delivery delay.

While portable and wireless devices are pouring, a new network technology is needed as a breakthrough. The new network technology features large delays, intermittent connectivity, and absence of an end-to-end path from sources to destinations. A network which has one of those characteristics is called DTNs(Delay Tolerant Networks). The main 4 routing methods have been researched so far in extreme environment. In this paper, we look into the reliability of DTMNs(Delay Tolerant Mobile Networks) in several different situations, and propose an algorithm that selects a positive routine by sending the only information of its position when making a connection to a detected node. We simulate the proposed algorithm here in DTN using ONE simulator. As a result, it shows that the algorithm reduces the number of message transmission each node.

Routing is one of the most challenging problems in Delay-Tolerant Networks (DTNs) due to network partitioning and intermittent connectivity. Most existing protocols are based on unlimited bandwidth. Previous protocols based on limited bandwidth (MaxProp, RAPID, etc) only consider the scenario that each node has at most one contact opportunity during any time interval, and discuss the packet scheduling mechanisms for each separate contact to minimize the average delivery delay. However, in many applications of DTNs, more than one contact opportunities with the same source node, which are called as related contact opportunities, may arise in the same time interval. But previous scheduling algorithms cannot apply to such applications. Therefore, we propose a more general scheduling algorithm to optimize the delivery delay in bandwidth limited DTNs including the scenario that multiple related contact opportunities may arise in the same interval, called Flow-Based Transmission Scheduling (FBTS). We evaluate it on publicly available data sets against MED, MaxProp and RAPID. The results show that the delivery delay of FBTS is at least 35% shorter than that of existing works.

Congestion-free routing of packets across a Wireless Sensor Network (WSN) is an important issue to be addressed for quick response applications such as disaster management, healthcare systems, traffic control, etc. The existing routing algorithms have been developed by mainly considering hop-count leading to a gap in addressing congestion problem in the routing process. Congestion during routing leads to increase in packet drops, increased energy consumption and delay in delivery of packets at the sink node. Therefore, it is necessary to propose an optimal congestion aware routing mechanism that considers network parameters such as congestion level and energy dissipation in addition to hop count factor. Hence in this paper, a traffic prudent framework called Congestion Aware Routing using Fuzzy Rule sets (CARF) has been proposed for handling excess traffic conditions by identifying the non-localized node paths, there after adding them to the existing localized node paths and selecting a more reliable and a congestion alleviated path to sink node using fuzzy rule prediction. This results in reducing packet drops and increasing energy utilization. The proposed framework CARF is organized into two operational segments namely 1) Multiple Path Identification by positioning non-localized nodes and 2) Congestion Mitigated routing of data packets to sink node. First operation employs the Positioning of a Non-Localized node algorithm that is used to compute the unknown coordinates of a sensor node thereby utilizing them to form more packet transmission paths in addition to the existing paths. The Point In Which Side (PIWS) hop count-based geometric method is utilized here for finding non-localized nodes in the sensor network. Second operation uses an Enhanced Fuzzy-based Congestion Mitigation (ECFM) algorithm for estimation of congestion level in nodes using fuzzy rule sets by considering incoming data packets per second, bandwidth size and path reliability. This CARF framework has been simulated using NS-2 testbed. Depending on the two major network characteristics such as path reliability and congestion level, a network path is chosen for routing data packets. From the experiments conducted in this work, it is proved that the proposed CARF mainly alleviates congestion, besides reducing energy cost and interference such as shadowing and attenuation.

Many real world networks are characterized by long delays, frequent path breaks, mobility, and lack of infrastructure. Class of networks which can cope up with such environments are called Delay Tolerant Networks (DTN). Architectures with a separate bundle layer, have been implemented in specific applications such as interplanetary networks (IPNs). However, the addition of bundle layer to existing network infrastructure still remains as a challenge. In this paper, we propose Dual-mode TCP which can work in both normal and DTN modes. It analyzes the network behavior and switches to DTN mode when the network exhibits DTN characteristics. For the estimation of network characteristics, Dual-mode TCP analyzes the RTT values and models the network based on RTTs normal distribution. If the network is found to be in DTN mode, the protocol uses a DTN congestion window to get adapted with the high delay environment. The advantage of Dual-mode TCP over traditional TCP is its ability to adapt with DTN environments while preserving the compatibility of TCP. We implemented Dual-mode TCP using light-weight IP and our results show that, in DTN environments, an average improvement of 11.64% in total transmission time can be achieved using Dual-mode TCP as compared to traditional TCP. With varying duration of link delays Dual-mode TCP achieves an average reduction of 36.19% in transmission time.

There is a growing need for secure and robust networks that function in austere environments or with nodes that have limited resources. The prime example is Delay Tolerant Networks that have military, first response, infrastructure failure and vehicle applications. This class of networks requires the modification of traditional routing and security protocols, such as TCP/IP or the use of certificate revocation servers, to effectively transmit a message from source to destination in a secure manner. There are multiple trust and routing schemes proposed for use in Delay Tolerant Networks. Here, we show how trust, usually defined in the context of network science, can be utilized for routing in Delay Tolerant Networks in which the fundamental challenge is balancing energy, delivery rate, delivery delay and security. Trust is a cornerstone of our approach to address this challenge. We propose a Trust Based Secure Routing Protocol, in which forwarding decisions are based on nodes trust, expected destination meeting time and the number of already created copies of the message.

Researching on delay tolerant networks is an emerging field. Many researchers are dedicated to the approach of the routing algorithms and its applications. With sufficient energy in the core-nodes in the networks, a nested source spray and wait routing algorithm, which is ameliorated from source spray and wait routing algorithm, has been put forward in this paper. The simulation results indicate that by increasing the cost of energy consumption at the core-nodes, this routing algorithm has better performances in terms of delivery probability and the average delay.

Delay Tolerant Network (DTN) is developed to cope with intermittent connectivity and long delay in wireless networks. Due to limited bandwidth, connectivity and buffer space, DTN is vulnerable to flooding attack where malicious nodes flood the network with excess data to deplete the network resources. In this paper, we propose a detection scheme for flooding attack that piggybacks on an existing encounter record (ER)-based scheme of detecting blackhole attack. Nodes are required to exchange their histories of ER which record the sent messages during their previous encounters. As a result, flooding adversaries who send too many messages or replicas can be detected. Malicious nodes may hide their flooding by deleting unfavorable ERs. However, this leads to inconsistency in the sequence number and timestamp of the ERs. We use these observations to design the final scheme. Simulation results show that our solution can detect flooding attack at high accuracy. Due to the piggybacking feature, our scheme can be incorporated with existing security work to form a more robust misbehavior detection system that can detect multiple attacks with little additional overhead.

As mobile ad hoc networks (MANETs) grow more popular and are deployed as solutions in various applications such as road safety (vehicular networks), wildlife tracking (wireless sensor networks) and device-to-device communications in 5G, the need for efficient routing that is robust against malfunctioning or malicious network nodes is increasing. We propose a security aware fuzzy enhanced ant colony optimization (SAFEACO) routing algorithm, which makes use of a fuzzy logic module to identify misbehaving nodes and exclude them from the routing process. We evaluate the SAFEACO routing algorithm, by comparing it with another modern and widely known approach and found that it shows superior performance in all relevant metrics, such as packet delivery ratio, delay and overhead. Due to its ability to identify misbehaving nodes, SAFEACO also provides a higher level of robustness against black hole and Sybil attacks.

Congestion control is an important factor for performance improvement in wireless sensor networks (WSNs). Congestion occurs due to various reasons including a variation in the data rate between incoming and outgoing links, buffer size, flooding attacks and multiple inputs and minimum output capability. Various outcomes of congestion in sensor networks include immense packet loss or packet drop, fast energy depletion, unfairness across the network, reduced node performance and increased delay in packet delivery. Hence, there is an extreme need to check channel congestion in order to enhance the performance with better congestion management. The job of choosing a suitable congestion control technique is a challenging task for the network designer. In this article, the authors traverse through the underlying conceptual ideas on congestion control schemes which come under six unique models. This article highlights a survey on the existing works done so far on congestion control domains in sensor networks. A comparative analysis based on Quality of Service parameters has been discussed.

Location Privacy breach in Wireless Sensor Networks (WSNs) cannot be controlled by encryption techniques as all the communications are signal based. Signal strength can be analyzed to reveal many routing information. Adversary takes advantage of this and tracks the incoming packet to know the direction of the packet. With the information of location of origin of packets, the Source is also exposed which is generating packets on sensing any object. Thus, the location of subject is exposed. For protecting such privacy breaches, routing schemes are used which create anonymization or diverts the adversary. In this paper, we are using `Dummy' packets that will be inserted into real traffic to confuse the adversary. The dummy packets are such inserted that they encircle the Sink or Base Station. These Dummy packets are send with a value of TTL (Time To Live) field such that they travel only a few hops. Since adversary starts backtracking from the Sink, it will be trapped in the dummy traffic. In our protocol, we are confusing adversary without introducing any delay in packet delivery. Adversary uses two common methods for knowing the source i.e. Traffic Analysis and Back-tracing. Mathematically and experimentally, our proposal is sound for both type of methods. Overhead is also balanced as packets will not live long.