Efficient Routing Protocol in Delay Tolerant Networks (DTNs)

Modern Internet protocols demonstrate inefficient performance in those networks where the connectivity between end nodes has intermittent property due to dynamic topology or resource constraints. Network environments where the nodes are characterized by opportunistic connectivity are referred to as Delay Tolerant Networks (DTNs). Highly usable in numerous practical applications such as low-density mobile ad hoc networks, command/response military networks and wireless sensor networks, DTNs have been one of the growing topics of interest characterized by significant amount of research efforts invested in this area over the past decade. Routing is one of the major components significantly affecting the overall performance of DTN networks in terms of resource consumption, data delivery and latency. Over the past few years a number of routing protocols have been proposed. The focus of this thesis is on description, classification and comparison of these protocols. We discuss the state-of-the-art routing schemes and methods in opportunistic networks and classify them into two main deterministic and stochastic routing categories. The classification is based on forwarding decisions in routing methods adopted with or without the knowledge about the network topology and nodes trajectories. The protocols in each class have their own advantages and shortcomings. In the stochastic routing protocols category, simple flooding-based protocols are feasible approaches in those networks where there is a little or no information about the network topology and there is no resource restriction. Epidemic routing is a flooding- based protocol relying upon the distribution of messages through the networks to deliver information to their destinations. To demonstrate the performance of the epidemic routing protocol for information delivery in networks with intermittent connectivities, we provide several simulation experiments and show that this protocol with reasonable aggregate resource consumption, ensures eventual message delivery in networks, using minimal assumptions regarding nodes trajectories, network topology and connectivity of underlying networks and only based on sufficient number of random pair-wise exchanges of messages among mobile nodes. In the following, we introduce the recently proposed network coding concept and discuss coding-based information delivery advantages in wireless networks. Network coding is a recently introduced paradigm to efficiently disseminate data in wireless networks in which data flows coming from multiple sources are combined to increase throughput, reduce delay, and enhance robustness against node failures. Finally, we present some simulation experiments to show the superiority of network coding for information delivery in wireless networks, compared to pure flooding-based mechanisms. /Kir1

Comparative analysis of attack detection methods in Delay Tolerant Network

Delay Tolerant Network is a new kind of wireless network which includes Radio Frequency (RF) and acoustic (sonar) technologies. DTN developed for an interplanetary network where the speed of light is slow. DTN is derived from deep space communication. DTN is distinguished as long delay and intermittent connectivity. The Delay Tolerant Network is more vulnerable to different kinds of attacks like flooding attack, blackhole and greyhole attacks, due to limited connectivity. There is no end-to-end connectivity between source & destination in DTN. So that it uses a store, carry and forward mechanism to transfer the data from one node to another node. The Delay Tolerant Network was developed to solve technical problems in the end-to-end network. DTN is becoming more and more important because communication networks are ubiquitous today. It provides automotive communication solutions. DTN is a decentralized and self-managed system with unique network attributes; however, attributes such as high mobility nodes, network uplinks and downlinks, and separate routing can cause network vulnerabilities. These vulnerabilities include the host being compromised, which in turn will bring security risks, because the compromised host may destroy the routing protocol in the network. This article analyses the various types of attack detection methods

Comparative analysis of attack detection methods in Delay Tolerant Network

Delay Tolerant Network is a new kind of wireless network which includes Radio Frequency (RF) and acoustic (sonar) technologies. DTN developed for an interplanetary network where the speed of light is slow. DTN is derived from deep space communication. DTN is distinguished as long delay and intermittent connectivity. The Delay Tolerant Network is more vulnerable to different kinds of attacks like flooding attack, blackhole and greyhole attacks, due to limited connectivity. There is no end-to-end connectivity between source & destination in DTN. So that it uses a store, carry and forward mechanism to transfer the data from one node to another node. The Delay Tolerant Network was developed to solve technical problems in the end-to-end network. DTN is becoming more and more important because communication networks are ubiquitous today. It provides automotive communication solutions. DTN is a decentralized and self-managed system with unique network attributes; however, attributes such as high mobility nodes, network uplinks and downlinks, and separate routing can cause network vulnerabilities. These vulnerabilities include the host being compromised, which in turn will bring security risks, because the compromised host may destroy the routing protocol in the network. This article analyses the various types of attack detection methods

Information-centric communication in mobile and wireless networks

Information-centric networking (ICN) is a new communication paradigm that has been proposed to cope with drawbacks of host-based communication protocols, namely scalability and security. In this thesis, we base our work on Named Data Networking (NDN), which is a popular ICN architecture, and investigate NDN in the context of wireless and mobile ad hoc networks. In a first part, we focus on NDN efficiency (and potential improvements) in wireless environments by investigating NDN in wireless one-hop communication, i.e., without any routing protocols. A basic requirement to initiate informationcentric communication is the knowledge of existing and available content names. Therefore, we develop three opportunistic content discovery algorithms and evaluate them in diverse scenarios for different node densities and content distributions. After content names are known, requesters can retrieve content opportunistically from any neighbor node that provides the content. However, in case of short contact times to content sources, content retrieval may be disrupted. Therefore, we develop a requester application that keeps meta information of disrupted content retrievals and enables resume operations when a new content source has been found. Besides message efficiency, we also evaluate power consumption of information-centric broadcast and unicast communication. Based on our findings, we develop two mechanisms to increase efficiency of information-centric wireless one-hop communication. The first approach called Dynamic Unicast (DU) avoids broadcast communication whenever possible since broadcast transmissions result in more duplicate Data transmissions, lower data rates and higher energy consumption on mobile nodes, which are not interested in overheard Data, compared to unicast communication. Hence, DU uses broadcast communication only until a content source has been found and then retrieves content directly via unicast from the same source. The second approach called RC-NDN targets efficiency of wireless broadcast communication by reducing the number of duplicate Data transmissions. In particular, RC-NDN is a Data encoding scheme for content sources that increases diversity in wireless broadcast transmissions such that multiple concurrent requesters can profit from each others’ (overheard) message transmissions. If requesters and content sources are not in one-hop distance to each other, requests need to be forwarded via multi-hop routing. Therefore, in a second part of this thesis, we investigate information-centric wireless multi-hop communication. First, we consider multi-hop broadcast communication in the context of rather static community networks. We introduce the concept of preferred forwarders, which relay Interest messages slightly faster than non-preferred forwarders to reduce redundant duplicate message transmissions. While this approach works well in static networks, the performance may degrade in mobile networks if preferred forwarders may regularly move away. Thus, to enable routing in mobile ad hoc networks, we extend DU for multi-hop communication. Compared to one-hop communication, multi-hop DU requires efficient path update mechanisms (since multi-hop paths may expire quickly) and new forwarding strategies to maintain NDN benefits (request aggregation and caching) such that only a few messages need to be transmitted over the entire end-to-end path even in case of multiple concurrent requesters. To perform quick retransmission in case of collisions or other transmission errors, we implement and evaluate retransmission timers from related work and compare them to CCNTimer, which is a new algorithm that enables shorter content retrieval times in information-centric wireless multi-hop communication. Yet, in case of intermittent connectivity between requesters and content sources, multi-hop routing protocols may not work because they require continuous end-to-end paths. Therefore, we present agent-based content retrieval (ACR) for delay-tolerant networks. In ACR, requester nodes can delegate content retrieval to mobile agent nodes, which move closer to content sources, can retrieve content and return it to requesters. Thus, ACR exploits the mobility of agent nodes to retrieve content from remote locations. To enable delay-tolerant communication via agents, retrieved content needs to be stored persistently such that requesters can verify its authenticity via original publisher signatures. To achieve this, we develop a persistent caching concept that maintains received popular content in repositories and deletes unpopular content if free space is required. Since our persistent caching concept can complement regular short-term caching in the content store, it can also be used for network caching to store popular delay-tolerant content at edge routers (to reduce network traffic and improve network performance) while real-time traffic can still be maintained and served from the content store

Network coding-based survivability techniques for multi-hop wireless networks

Multi-hop Wireless Networks (MWN) have drawn a lot of attention in the last decade, and will continue to be a hot and active research area in the future also. MWNs are attractive because they require much less effort to install and operate (compared to wired networks), and provide the network users with the flexibility and convenience they need. However, with these advantages comes a lot of challenges. In this work, we focus on one important challenge, namely, network survivability or the network ability to sustain failures and recover from service interruption in a timely manner. Survivability mechanisms can be divided into two main categories; Protection and restoration mechanisms. Protection is usually favored over restoration because it usually provides faster recovery. However, the problem with traditional protection schemes is that they are very demanding and consume a lot of network resources. Actually, at least 50% of the used resources in a communication session are wasted in order to provide the destination with redundant information, which can be made use of only when a network failure or information loss occurs. To overcome this problem and to make protection more feasible, we need to reduce the used network resources to provide proactive protection without compromising the recovery speed. To achieve this goal, we propose to use network coding. Basically, network coding allows intermediate network nodes to combine data packets instead of just forwarding them as is, which leads to minimizing the consumed network resources used for protection purposes. In this work we give special attention to the survivability of many-to-one wireless flows, where a set of N sources are sending data units to a common destination T. Examples of such many-to-one flows are found in Wireless Mesh Networks (WMNs) or Wireless Sensor Networks (WSNs). We present two techniques to provide proactive protection to the information flow in such communication networks. First, we present a centralized approach, for which we derive and prove the sufficient and necessary conditions that allows us to protect the many-to-one information flow against a single link failure using only one additional path. We provide a detailed study of this technique, which covers extensions for more general cases, complexity analysis that proves the NP-completeness of the problem for networks with limited min-cuts, and finally performance evaluation which shows that in the worst case our coding-based protection scheme can reduce the useful information rate by 50% (i.e., will be equivalent to traditional protection schemes). Next, we study the implementation of the previous approach when all network nodes have single transceivers. In this part of our work we first present a greedy scheduling algorithm for the sources transmissions based on digital network coding, and then we show how analog network coding can further enhance the performance of the scheduling algorithm. Our second protection scheme uses deterministic binary network coding in a distributed manner to enhance the resiliency of the Sensors-to-Base information flow against packet loss. We study the coding efficiency issue and introduce the idea of relative indexing to reduce the coding coefficients overhead. Moreover, we show through a simulation study that our approach is highly scalable and performs better as the network size and/or number of sources increases. The final part of this work deals with unicast communication sessions, where a single source node S is transmitting data to a single destination node T through multiple hops. We present a different way to handle the survivability vs. bandwidth tradeoff, where we show how to enhance the survivability of the S-T information flow without reducing the maximum achievable S-T information rate. The basic idea is not to protect the bottleneck links in the network, but to try to protect all other links if possible. We divide this problem into two problems: 1) pre-cut protection, which we prove it to be NP-hard, and thus, we present an ILP and a heuristic approach to solve it, and 2) post-cut protection, where we prove that all the data units that are not delivered to T directly after the min-cut can be protected against a single link failure. Using network coding in this problem allows us to maximize the number of protected data units before and after the min-cut