Performance Evaluation of DTN Routing Protocols in Vehicular Network Environment

Delay/disruption tolerant networking (DTN) is a class of network techniques developed to accommodate long link delay and frequent link disruptions. Little work has been done in evaluating the effectiveness and performance of the DTN protocols when they are applied for an interplanetary Internet (IPN). In this paper, we present an experimental evaluation of Transmission Control Protocol Convergence Layer (TCPCL)-based operation of DTN-2 (i.e., TCPCL/TCP) for long-delay cislunar communications, partially in comparison with Licklider Transmission Protocol (LTP)-based LTP/User Datagram Protocol (UDP). The experiment is conducted by transmitting a text file using the DTN protocol stack over a PC-based simulation test-bed. According to the experimental results, the TCPCL-based DTN protocol works effectively over less error-prone cislunar links with short delay and has performance advantage over LTP-based DTN. Along with the increase in link delay and channel noise, the performance of TCPCL-based DTN is getting far behind the LTP-based DTN. The TCPCL-based DTN protocol can successfully handle an experimented short link disruption around 30 s-120 s, even with an existence of a very long link delay and a high channel Bit-Error-Rate (BER), but its performance is poor compared to that of the LTP-based DTN.

The storage resources and communication opportunities in space delay/disruption tolerant networks (DTN) are usually very limited. Moreover, as the links in space DTN are often subject to long delay, intermittent connectivity and asymmetric bandwidth, end-to-end continuous path may not be guaranteed and messages may stay at intermediate nodes for a long time. Thus, congestion in space DTN, which takes the form of persistent storage exhaustion, is inevitable. Due to the intrinsic features of space DTN, congestion control should be performed with local information before congestion occurs and limited storage and communication resources should be allocated to messages that have the highest probability to be delivered to destination. Based on these principles, a local information-based congestion control (LCC) scheme for space DTN is proposed in this paper. Firstly, LCC attempts to relieve the storage pressure by using alternative paths i.e. non-best paths when the network is about to congest. Secondly, LCC adopts a utility function based on the reciprocal of hop counts to destination to assist forwarding decision and queue management. Simulation results show that with the combination of LCC typical space DTN routing algorithm can achieve higher message delivery ratio and more uniform traffic distribution.

Delay/disruption tolerant network (DTN), in which the network connectivity is intermittent and the node buffer size is limited, is a promising approach to model space networks. In this study, the authors focus on the space deterministic DTNs whose mobility and connectivity are predictable. A rate adaptation scheme based on adaptive modulation and coding (AMC) is adopted. Based on the analysis of data delay in DTN, the authors propose two routing algorithms, namely local information‐based routing (LIR) and local and neighbour information‐based routing (LNIR) for space DTNs. Queuing information in partial nodes is used in routing selection. The two proposed algorithms outperform the traditional least delay routing (LDR) in average end‐to‐end delay, packet loss ratio and traffic distribution. With the same network load, the average delay of LDR, LIR and LNIR are 44.43s, 22.82s and 14.08s while the packet loss ratio of three algorithms are 6.37, 0.76 and 0.00%. Simulation result also shows the superiority of AMC over fixed modulation and coding (FMC) in space DTNs. When the DTN is heavily loaded, the delay of AMC is 15 s smaller than that of FMC. At the same time, the packet loss ratio of AMC is one‐sixth that of FMC.

“Challenged networks” often violate the TCP design key assumption of continuous path availability from the source to the sink node. These networks are the preferred target of Delay/Disruption Tolerant Networking (DTN), which aims at providing a more robust network architecture. Against disruptions, however, even standard TCP offers a certain level of robustness, through its many retransmission algorithms. This intrinsic TCP resilience against disruptions is retained and enhanced if TCP is inserted in a DTN architecture. Focusing on this, the aim of the paper is to present an in-depth analysis of TCP and DTN bundle protocol retransmission algorithms that are triggered by channel disruptions, thus providing the reader with a comprehensive view of the many mechanisms involved and their complex interactions. The first sections, devoted to the description of TCP and DTN algorithms, are completed by the presentation of some numerical evaluations obtained by means of a Linux testbed. They refer to a GEO satellite environment and clarify the previous algorithm descriptions. Moreover, they also offer the reader some useful insights on both TCP and DTN resilience to disruptions, considering some performance metrics, like the “maximum tolerable disruption length” and the “restart delay”, introduced and explained in the paper.

The introduction of intelligent devices with short range wireless communication techniques has motivated the development of Mobile Ad hoc NETworks (MANETs) during the last few years. However, traditional end-to-end based routing algorithms designed for MANETs are not much robust in the challenged networks suffering from frequent disruption, sparse network density and limited device capability. Such challenged networks, also known as Intermittently Connected Networks (ICNs) adopt the Store-Carry-Forward (SCF) behavior arising from the mobility of mobile nodes for message relaying. In this article, we consider the term ICNs as Delay/Disruption Tolerant Networks (DTNs) for the purpose of generalization, since DTNs have been envisioned for different applications with a large number of proposed routing algorithms. Motivated by the great interest from the research community, we firstly review the existing unicasting issue of DTNs because of its extensive research stage. Then, we also address multicasting and anycasting issues in DTNs considering their perspectives. A detail survey based on our taxonomy over the period from 2006 to 2010 is not only provided but also a comparison is given. We further identify the remaining challenges and open issues followed by an evaluation framework proposed for routing in DTNs. Finally, we summarize our contribution with three future research topics highlighted.

Vehicle-to-vehicle networks have gained significant interest in recent times from researchers all around the world. V2V/V2I are emerging as an efficient solution for achieving road safety and securely transmitting data from one vehicle to other. However, in such opportunistic environments such as a sparse vehicular network where disruption, dynamic network topology, fast vehicle movement, and environmental conditions are the major concerns, data forwarding is extremely challenging. Traditional ad-hoc routing protocols like Ad hoc On-Demand Distance Vector (AODV) and Dynamic Source Routing (DSR) fail to deliver in such laborious conditions. Routing protocols of Delay/Disruption Tolerant Networks(DTN) exploit the Store-Carry-Forward Mechanism (SCF) strategy in these cases. Taking advantage of temporary connections to disseminate information is the focus of DTN. DTN helps to increase information propagation coverage in sparse areas where there are very few devices. In this paper, we first compare the performance of AllJoyn framework and Direct Delivery protocol in a single-hop scenario and then draw the attention towards a multi-hop scenario by comparing other three routing protocols that use DTN as the underlying paradigm. These protocols are Flooding, Epidemic, and PRoPHET. The performances are evaluated by transmitting the files of size 1, 4, and 10 MB from a static sender to a mobile receiver in the multi-hop scenario. We also develop an Android application that contains the implementation of these routing protocols along with file sharing functionality. From the outcomes of this experiment, it can be said that Epidemic routing protocol performs the best in our considered multi-hop scenario in terms of transfer delay, coverage, and throughput whereas, Direct Delivery routing protocol performs better than AllJoyn in single-hop communication.

In this paper, we evaluate and compare the performance of single-copy and multiple-copy routing protocols in a realistic Vehicular Delay Tolerant Network (VDTN) scenario. The simulations are conducted with the Opportunistic Network Environment (ONE) simulator. The performance is analyzed using delivery probability, overhead ratio, average latency, average number of hops and average buffer time metrics. The simulation results show that multiple-copy protocols perform better in terms of delivery probability compared with singlecopy protocol. The single-copy protocol uses the highest average number of hops and higher average latency compared with multiple-copy protocols. Maxprop achieves the highest delivery ratio and lowest average latency. Spray and wait results are the lowest for overhead ratio, but the longest for average buffer time. First contact have a short buffer time, but it uses a big number of hops.

Delay/Disruption Tolerant Networking (DTN) is an approach suitable for networks where end-to-end connections are not guaranteed. In this paper, the energy-based routing with rendezvous is proposed to improve delivery probability of important messages in DTN-based UAV networks. The main idea for achieving this goal is to introduce the rendezvous mode for DTN-based UAV networks, whether to hover or to follow. Simulation was performed using Opportunistic Network Environment (ONE). The simulation results showed that the proposed routing scheme with rendezvous has a larger delivery probability for important messages despite their sizes, compared to the previous routing scheme without rendezvous.

DTN (Delay/Disruption Tolerant Networking) inserts a new layer between the application layer (L7) and the transport layer (L4) for reliable communication on long-delay, intermittent, or lossy inks. Such a new layer, however, should provide not only a single rich service but also various rich services. We are proposing Layer-5 (L5) inserted between L7 and L4 to provide multiple rich services. One of the rich services of L5 is the L5 temporally-spliced path (L5-TSP). It is an application-to-application path composed of multiple L4 paths, which may not exist at the same time, spliced in L5 in the nodes called splicers. This paper proposes L5-TSP Protocol (L5-TSPP) for reliable communication on lossy links. L5-TSPP places splicers at both ends of a lossy link. It uses TCP on reliable links while UDP on lossy links. It uses partial acknowledgement to enable end nodes to know progress of communication. L5-TSPP is implemented on Linux. It takes 61 msec for connection establishment in L5-TSPP while 530 msec in TCP at packet loss rate of 10 % on a lossy link. It takes 18 sec to send a 1GB file in L5-TSPP while 73 sec in TCP at packet loss rate of 1 %.

The dissemination of redundant copies of a message is one of the techniques used in Delay/Disruption Tolerant Networks (DTN) to improve the delivery rate and to decrease the incurred delay. Nevertheless, many of these copies remain in the buffer of intermediate nodes even after the message is delivered to the destination. In this paper, we propose mechanism to remove obsolete messages for DTN routing protocols. Furthermore, we compare its performance with other state-of-art techniques under two different realistic scenarios and using two datasets of human mobility traces. Through the obtained results, we observed a better performance of the tested DTN routing protocols in most scenarios in terms of delivery ratio and overhead messages, when compared to others related works.

The Delay/Disruption Tolerant Networking (DTN) aims to provide inter-operable communications with wide range of networks which have poor performance characteristics. In this paper, we propose a message suppression method for Vehicular DTN (VDTN). The simulations for two scenarios are conducted considering obstacles (buildings), where Message Suppression with Road Side Units (MSRs) are present or not present. We consider 802.11p standard and send bundle messages in a realistic scenario of east side of Tokyo station area in Japan imported from open street map. We use the packet delivery ratio, duplicated bundle messages and end-to-end delay as evaluation metrics. We can observe that our proposed method can reduce the duplicated bundle messages, even if the number of vehicles is increased. Moreover, our message suppression method has almost the same packet delivery ratio with the Epidemic conventional method.

Information Retrieval (IR) systems aim to retrieve data that satisfies certain requirements and constitute an important service in many types of networks, including Delay/Disruption Tolerant Networks (DTNs). In current DTN based IR systems, the data that satisfies a query is assumed to be stored on a single node. Therefore, once a node receives a query in which it has the corresponding data, the query can be resolved completely. However, in scenarios where a query requires data from multiple nodes, these IR systems may fail. Henceforth, in this paper, we propose Distributed Data-Centric Information Retrieval (DDC-IR), a data centric IR system that supports all query types; e.g., continuous and complex. More importantly, it is designed specifically to operate in DTNs. It also incorporates a new packet, aka Query Reply Packet, that includes both a query and one or more replies. We show how this packet facilitates efficient query resolution and enables data centric routing. In addition, it uses caching so that nodes store popular queries that has the effect of speeding up query resolution. We have conducted an extensive simulation study to compare DDC-IR to state of the art IR systems using the popular Random Waypoint model and a trace-file containing student movements on a campus. The results show that DDC-IR is able to resolve 50 % more queries and has an 80 % lower buffer occupancy level than existing IR systems. We also tested DDC-IR in networks with varying sizes. For networks with 100 nodes, DDC-IR is able to resolve queries while current IR systems fail to resolve any queries. In particular, when the number of nodes increases, current IR systems fail to resolve any queries, whilst DDC-IR is able to resolve complex and continuous queries. The influence of the number of sub-queries on query resolution time is also studied. Specifically, when the number of sub-queries in a complex query increases from five to nine, DDC-IR uses 50 % more time to resolve a query. In comparison, prior IR systems fail to resolve any queries.

Recently, there has been focus on augmenting Delay/Disruption Tolerant Networks (DTNs) with easily deployable stationary relay nodes making an unconnected infrastructure to facilitate the data delivery by increasing forwarding opportunities. Relay nodes are capable of downloading, storing, and forwarding the data messages from/to the mobile nodes. Placing the relay nodes is an important issue in DTNs as the performance of the network is dependent to their positions. Relay placement is an NP-hard problem hence it makes it a more complicated issue in DTNs. Existing works in the literature are based on simulation which are suffering from computational complexities dictated by simulation. Moreover, they are optimizing the relay placement only based on specific scenarios. In this paper, we propose a generic analytical model in order to evaluate the performance of DTNs in presence of relay nodes. Our model is dependent on the mobile nodes' mobility pattern, and we consider the case when the mobile nodes move according to the random waypoint model. In order to use the proposed model for placing the relays efficiently, we utilize two heuristic approaches. The first approach is based on optimization of the network performance using simulated annealing and the second one relies on a greedy approach to find the best location for each relay one at a time. Our simulation results show that our approaches outperform the simulation based approaches in terms of data delivery performance.

Existing Internet protocols assume persistent end-to-end connectivity, which cannot be guaranteed in disruptive and high-latency space-terrestrial networks. To operate over these challenging networks, Delay/Disruption Tolerant Networking (DTN) architecture has been proposed. Although recent advances, evaluating DTN routing in large-scale networks spanning prolonged time-evolving topologies remain an unsolved issue. In this work, we introduce DtnSim, an event-driven DTN simulation tool that leverages routing models with flight-software routing algorithms implementations. This paper describes how DtnSim allows to conveniently and intuitively determine network flow metrics which otherwise would require complex prototyping and prolonged experiment times.

Message in delay/disruption tolerant network (DTN) is often transmitted in the store/carry/forward mode. In this mode, the transmission process includes two important steps (beaconing and forwarding). Both processes consume much energy which is very precious for the wireless application. At present, most of the works considers just one step in the controlling process (some ignore the beaconing control and some ignore the forwarding control). In addition, state-of-the-art works often assume that there is only one destination for a specific message. In this paper, we consider the optimal forwarding and beaconing control problem at the same time in DTN, where multiple destinations exist. In particular, based on whether those destinations are willing to relay message for others, we consider the selfish and altruistic cases, respectively. Based on these settings, we mathematically characterize this problem as an optimal control problem. The controlling parameters are the forwarding rate and beaconing rate, respectively. Then, we solve the problem by Pontryagin’s Maximum Principle, and mathematically prove that both the optimal forwarding and beaconing policies conform to the threshold form. Next, we check the accuracy of the theoretical models by simulations based on both synthetic and real motion traces. Finally, we check the result in a real scenario with 100 students, and show that the optimal policy can really improve the performance.