Delay/disruption Tolerant Networking Protocols Research Articles

Transmission Efficiency of Licklider Transmission Protocol (LTP) and Bundle Protocol (BP) in DTN Architecture

From Near-Earth orbit (NEO) to Earth-Sun Lagrangian points will continue to be a majority of Near Earth missions ranging from Near-Earth orbit (NEO) to Earth-Sun Lagrangian points will continue to be a majority of future space missions. A few works have been done with delay/disruption tolerant networking (DTN) technology for Near-Earth orbit (NEO)-space center and deep space communications and provided feasibility for its adoption in NEO-space and deep space missions. [1] However, no much work has been done to fully evaluate the transmission efficiency of DTN in such an environment, especially in the presence of long link disruption, data corruption and lost rate, and link asymmetry. In this paper, we present an experimental performance evaluation of DTN architecture and protocol stack, with Licklider transmission protocol (LTP) serving as a convergence layer adapter (CLA) underneath bundle protocol (BP), in typical NEO-satellite system and deep space communication infrastructures accompanied by a very long link delay, various packet corruption and lost rates, and channel rate symmetry and asymmetry. In addition, we present an experimental research of the transmission efficiency of DTN custody transfer with long link delay. The experiment was conducted by performing realistic file transfers over a virtual server-based test-bed.

Geo-DMP: A DTN-Based Mobile Prototype for Geospatial Data Retrieval

Geospatial information is gaining immense interest and importance as we enter the era of highly developed transportation and communication. Despite the proliferation of cellular network and WiFi, on some occasions, users still face barriers to accessing geospatial data. In this paper, we design and implement a distributed prototype system with a delay/disruption tolerant network (DTN), named Geo-DMP, for cooperatively and opportunistically sharing and exchanging named geospatial contents in a device-to-device fashion. First of all, we construct a lightweight “content agent” module to bridge the gap between the application layer and the underlying DTN protocol stack. Afterwards, to profile the mobility history of users in practical geospatial environments, we present a map segmentation scheme based on road network and administrative subdivision information. Subsequently, we associate the regional movement history information with the content retrieval process to devise a hierarchical and region-oriented DTN routing scheme for both requests and responses. Finally, we conduct extensive experiments with real-world trajectories and complete implementations on the emulation platform composed of virtual machines. The experiments corroborate that Geo-DMP has the capability of successfully retrieving geospatial contents for users for most of the time under mobile circumstances with episodic connectivity. Moreover, en-route caches can be efficiently exploited to provision contents from multiple sources with less network resource consumption and shorter user-perceived latencies.

Performance of Bundle Protocol (BP) for deep space communications with long link disruptions

Near Earth missions and deep space missions will continue to be a major future space mission. A long link disruption is inevitable in space communications because of spacecraft rotation, planetary bodies and limited relay capability. A few works have been done with delay/disruption tolerant networking (DTN) technology for deep space communications and provided feasibility for its adoption in LEO- space and deep space missions. However, not much work has been done to fully evaluate the performance of DTN in such an environment, especially in the presence of custody and long link transfer. In this article, we present an experimental performance evaluation of DTN architecture and protocol stack with DTN custody transfer and long link break underneath bundle protocol (BP), in typical LEO-satellite and deep space communication infrastructures accompanied. The experiment was conducted by performing realistic file transfers over a PC-based test-bed.

Queueing analysis of DTN protocols in deep-space communications

Delay/disruption tolerant networking (DTN) [1] is proposed as an internetworking architecture for reliable data delivery despite a long propagation delay and/or lengthy link disruptions. DTN targets challenging networking environments where traditional networking protocols such as the terrestrial Transmission Control Protocol/Internet Protocol (TCP/IP) typically do not work effectively. The challenging problem of mission control and data delivery in space communications is a typical application scenario of the DTN technology. Reliable and highly efficient data delivery of DTN relies heavily on the bundle protocol (BP) [2]. BP is intended to establish an overlay network that is able to withstand intermittent data link connectivity in the delivery of DTN data units, termed bundles. BP adopts a store-and-forward mechanism and a custody transfer option for transmission reliability.

Optimal RTO Timer for Best Transmission Efficiency of DTN Protocol in Deep-Space Vehicle Communications

The delay/disruption-tolerant network (DTN) was proposed as an end-to-end networking architecture for file delivery service in a stressed communication environment. A typical application of DTN technology is for reliable data delivery in deep-space vehicle communications. The main protocol of DTN, i.e., bundle protocol (BP), utilizes a store-and-forward mechanism and a custody transfer option for transmission reliability. However, little work has been done on the performance evaluation of DTN's BP in deep-space communications. In this paper, we present a study of the retransmission timeout (RTO) timer setting for the use of BP for reliable file (or data) transmission over a relay-based deep-space vehicle communication infrastructure characterized by extremely long latency, lossy data links, and highly asymmetric channel rates. Unlike most studies proposed for terrestrial Internet for which the RTO timer is set equal to or longer than the round-trip time (RTT), we propose to set the RTO timer shorter than the RTT and expect that it will increase delivery efficiency per unit of time. We intend to find an RTO timer setting for maximum data delivery performance of BP, which is considered to be an optimal RTO timer, for deep-space missions. For the first time, analytical models are built for delivery performance involving the RTO timer. Using the built models, we tune the RTO timer toward the highest data delivery performance. The models are validated by running text file transfer experiments using a PC-based testbed and tuning the RTO timer toward the best performance of BP. A performance comparison between the optimal RTO timer proposed in this study and the existing commonly used RTO timers is also presented.

Public‐key infrastructure validation and revocation mechanism suitable for delay/disruption tolerant networks

Public-key infrastructure (PKI) is based on public-key certificates and is the most widely used mechanism for trust and key management. However, standard PKI validation and revocation mechanisms are considered major reasons for its unsuitability for delay/disruption tolerant networking (DTN). DTN requires mechanism to authenticate messages at each node before forwarding it in the network. So, certificate revocation lists (CRLs) being distributed in DTN network will need to be authenticated and validated for issuer certificate authority (CA) at each node. In this study, the authors propose new validation and revocation mechanism which is compliant with DTN semantics and protocols. This study also proposes a new design for CRL in compliance with standard PKI X.509 standard to make the proposed mechanism easy to implement for DTN. The new designed CRL is of reduced size as it contains fewer entries as compared with standard X.509 CRL and also arranges the revocation list in the form of hash table (map) to increase the searching efficiency.

Performance modeling of licklider transmission protocol (LTP) in deep-space communication

Delay/disruption tolerant networking (DTN) offers a solution to communications in “challenged” networks. Some work has been seen in evaluating the performance of DTN protocols based on simulated or emulated file transfer experiments. However, there is a need for a model of the performance of the DTN Licklider transmission protocol (LTP), which particularly targets reliable data transmission in deep space. In this paper, we present a performance model of LTP-based DTN data transmission in challenging communications characterized by extremely long signal propagation delay, lengthy link disruptions, and highly lossy channels that are typical of deep-space links. The model is verified by file-transfer experiments using a PC-based testbed.

Analytical characterization of licklider transmission protocol (LTP) in cislunar communications

The performance of delay/disruption tolerant networking (DTN) protocols in cislunar and deep-space communication systems has previously been studied by simulation. However, little work has been seen in characterizing in an analytical manner the performance of DTN protocols for space with respect to asymmetric channel rates. We present a performance characterization of the recently developed DTN Licklider transmission protocol (LTP) convergence layer adapter (CLA) (or simply LTPCL) over cislunar space channels with data-rate asymmetry. Analytical models are built to characterize LTPCL with respect to the minimum number of bundle protocol (BP) bundles that should be aggregated to avoid delay in acknowledgment (ACK) transmission and the optimal number of bundles to be aggregated for the best transmission efficiency of BP/LTPCL, with the effect of full overhead at all layers taken into consideration. The models are validated by file transfer experiments running BP/LTPCL protocols using a PC-based testbed.

Evaluation of the Average Packet Delivery Delay in Highly-Disrupted Networks: The DTN and IP-like Protocol Cases

Delay/Disruption-Tolerant Networking (DTN) represents an innovative communication paradigm that enables the communication over Intermittently-Connected Networks (ICNs). ICNs are characterized by unpredictable or scheduled contacts among nodes, high latency, and high bit error rates. DTNs, unlike TCP/IP protocols, make use of store-and-forward techniques in order to cope with intermittent link issues. In this letter, a simple model is proposed to compute the average packet delivery delay in ICNs. Both the IP-like paradigm used by traditional TCP/IP protocols and DTN are considered. The results provide theoretical insights into the applications of these two approaches to ICNs. Numerical results and simulations are presented, too.

Performance of DTN protocols in space communications

Delay/disruption tolerant networking (DTN) was developed to enable automated network communications despite the long link delay and frequent link disruptions that generally characterize space communications. The performance of DTN convergence layer adapter (CLA) protocols over asymmetric space communication channels has not yet been comprehensively characterized. In this paper, we present an experimental performance evaluation of DTN CLA protocols for reliable data transport over a space communication infrastructure involving asymmetric channel rates, with particular attention to the recently developed Licklider transmission protocol (LTP) CLA (i.e., LTPCL). The performance of LTPCL is evaluated in comparison with other two reliable CLAs, TCP CLA and a hybrid of TCP CLA and LTPCL, for long-delay cislunar communications in the presence of highly asymmetric channel rates. LTPCL is also evaluated and analyzed in a deep-space communication scenario characterized by a very long link delay and lengthy link disruptions.

A store-carry-process-and-forward paradigm for intelligent sensor grids

Store-carry-and-forward DTN (Delay/Disruption Tolerant Networking) protocols offer new possibilities in scenarios where there is intermittent connectivity, asymmetric bandwidths, long and variable latency and ambiguous mobility patterns. In this article we propose a new paradigm –store-carry-process-and-forward – based on mobile code to improve the integration of wireless sensor networks and grid computing infrastructures. We describe the implementation of a delay tolerant grid service, the computer element, to give computing access to an intermittently connected wireless sensor network. The result is an intelligent system which adapts dynamically to intermittent disconnections and improves multi-application coexistence. Finally, we present as an example a real case application which provides general purpose grid access to a multi-application mobile robot node sensor network.

Licklider Transmission Protocol (LTP)-Based DTN for Cislunar Communications

Delay/disruption-tolerant networking (DTN) technology offers a new solution to highly stressed communications in space environments, especially those with long link delay and frequent link disruptions in deep-space missions. To date, little work has been done in evaluating the performance of the available “convergence layer” protocols of DTN, especially the Licklider Transmission Protocol (LTP), when they are applied to an interplanetary Internet (IPN). In this paper, we present an experimental evaluation of the Bundle Protocol (BP) running over various “convergence layer” protocols in a simulated cislunar communications environment characterized by varying degrees of signal propagation delay and data loss. We focus on the LTP convergence layer (LTPCL) adapter running on top of UDP/IP (i.e., BP/LTPCL/UDP/IP). The performance of BP/LTPCL/UDP/IP in realistic file transfers over a PC-based network test bed is compared to that of two other DTN protocol stack options, BP/TCPCL/TCP/IP and BP/UDPCL/UDP/IP. A statistical method of t-test is also used for analysis of the experimental results. The experiment results show that LTPCL has a significant performance advantage over Transmission Control Protocol convergence layer (TCPCL) for link delays longer than 4000 ms regardless of the bit error rate (BER). For a very lossy channel with a BER of around 10-5, LTPCL has a significant goodput advantage over TCPCL at all the link delay levels studied, with an advantage of around 3000 B/s for delays longer than 1500 ms. LTPCL has a consistently significant goodput advantage over UDPCL, around 2500-3000 B/s, at all levels of link delays and BERs.

Experimental Evaluation of TCP-Based DTN for Cislunar Communications in Presence of Long Link Disruption

Delay/disruption tolerant networking (DTN) technology is considered a new solution to highly stressed communications in space environments. To date, little work has been done in evaluating the effectiveness and performance of the available DTN protocols when they are applied to an interplanetary Internet, especially in presence of a long link disruption. In this paper, we present an experimental investigation of the DTN architecture with a Bundle Protocol (BP) running over TCP-based convergence layer (TCPCL) protocol in a simulated cislunar communication environment characterized by a long link disruption. The intent of this work is to investigate the effectiveness of the TCPCL-based DTN protocol in coping with long link disruptions, through realistic file transfer experiments using a PC-based test-bed. The experiment results show that the DTN protocol is effective in handling a long link disruption experienced in data transmission accompanied by a cislunar link delay and a high BER. The performance of the DTN is most adversely affected by link disruption time in comparison to the effect of link delay and BER. For the transmissions with a very long link disruption of hours, the variations in goodput are nominal with respect to the change in cislunar link delay.

TCP Convergence Layer-Based Operation of DTN for Long-Delay Cislunar Communications

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.

HYMAD: Hybrid DTN-MANET routing for dense and highly dynamic wireless networks

Delay/Disruption-Tolerant Network (DTN) protocols typically address sparse intermittently connected networks whereas Mobile Ad-hoc Network (MANET) protocols address the fairly stable and fully connected ones. But many intermediate situations may occur on mobility dynamics or radio link instability. In such cases, where the network frequently splits into evolving connected groups, none of the conventional routing paradigms (DTN or MANET) are fully satisfactory. In this paper we propose HYMAD, a Hybrid DTN-MANET routing protocol which uses DTN between disjoint groups of nodes while using MANET routing within these groups. HYMAD is fully decentralized and only makes use of topological information exchanges between the nodes. The strength of HYMAD lies in its ability to adapt to the changing connectivity patterns of the network. We evaluate the scheme in simulation by replaying synthetic and real life mobility traces which exhibit a broad range of connectivity dynamics. The results show that HYMAD introduces limited overhead and outperforms the multi-copy Spray-and-Wait DTN routing protocol it extends, both in terms of delivery ratio and delay. This hybrid DTN-MANET approach offers a promising venue for the delivery of elastic data in mobile ad-hoc networks as it retains the resilience of a pure DTN protocol while significantly improving performance.