DTN performance analysis of multi‐asset Mars‐Earth communications

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On Applications of Disruption Tolerant Networking to Optical Networking in Space

The integration of optical communication links into space networks via Disruption Tolerant Networking (DTN) is a largely unexplored area of research. Building on successful foundational work accomplished at JPL, we discuss a multi-hop multi-path network featuring optical links. The experimental test bed is constructed at the NASA Glenn Research Center featuring multiple Ethernet-to-fiber converters coupled with free space optical (FSO) communication channels. The test bed architecture models communication paths from deployed Mars assets to the deep space network (DSN) and finally to the mission operations center (MOC). Reliable versus unreliable communication methods are investigated and discussed; including reliable transport protocols, custody transfer, and fragmentation. Potential commercial applications may include an optical communications infrastructure deployment to support developing nations and remote areas, which are unburdened with supporting an existing heritage means of telecommunications. Narrow laser beam widths and control of polarization states offer inherent physical layer security benefits with optical communications over RF solutions. This paper explores whether or not DTN is appropriate for space-based optical networks, optimal payload sizes, reliability, and a discussion on security

Performance Assessment of Aggregation and Deaggregation Algorithms in Vehicular Delay-Tolerant Networks

Vehicular Delay-Tolerant Networks (VDTNs) are a new approach for vehicular communications where vehicles cooperate with each other, acting as the communication infrastructure, to provide low-cost asynchronous opportunistic communications. These communication technologies assume variable delays and bandwidth constraints characterized by a non-transmission control protocol/ internet protocol architecture but interacting with it at the edge of the network. VDTNs are based on the principle of asynchronous communications, bundleoriented communication from the DTN architecture, employing a store-carryand- forward routing paradigm. In this sense, VDTNs should use the tight network resources optimizing each opportunistic contact among nodes. At the ingress edge nodes, incoming IP Packets (datagrams) are assembled into large data packets, called bundles. The bundle aggregation process plays an important role on the performance of VDTN applications. Then, this paper presents three aggregation algorithms based on time, bundle size, and a hybrid solution with combination of both. Furthermore, the following four aggregation schemes with quality of service (QoS) support are proposed: 1) single-class bundle with N = M, 2) composite-class bundle with N = M, 3) single-class bundle with N > M, and 4) composite-class bundle with N > M, where N is the number of classes of incoming packets and M is the number of priorities supported by the VDTN core network. The proposed mechanisms were evaluated through a laboratory testbed, called VDTN@Lab. The adaptive hybrid approach and the composite-class schemes present the best performance for different types of traffic load and best priorities distribution, respectively

Multicolor Licklider Transmission Protocol: An LTP Version for Future Interplanetary Links

The Licklider Transport Protocol (LTP) is the "convergence layer" of choice in Interplanetary networks based on Delay-/Disruption-Tolerant architecture. It was designed for long-delay scheduled-intermittent links, offering either a reliable or an unreliable service, with "red" and "green" parts, respectively. The aim of this article is to present multicolor LTP, an LTP version consisting in a series of enhancements of which the most significant are the use of monochrome sessions, the introduction of an additional orange color offering a "notified" service, and the definition of default link colors. After a thorough examination of basic LTP mechanisms for all color variants, this article discusses two scenarios where orange seems particularly appealing: video streaming and optical interplanetary links. Numerical results offer further insight into the complex LTP mechanisms and also highlight the difference between LTP retransmissions and bundle protocol retransmissions, the latter benefitting from routing reprocessing. Multicolor LTP has already been implemented as an interplanetary overlay network (ION) plug-in and its enhancements have been proposed to Consultative Committee for Space Data Systems Space Internetworking Services Delay-/Disruption-Tolerant Networking working group for a possible inclusion in the next version of LTP specifications (LTPv2)

Security Analysis of DTN Architecture and Bundle Protocol Specification for Space-Based Networks

A Delay-Tolerant Network (DTN) Architecture (Request for Comment, RFC-4838) and Bundle Protocol Specification, RFC-5050, have been proposed for space and terrestrial networks. Additional security specifications have been provided via the Bundle Security Specification (currently a work in progress as an Internet Research Task Force internet-draft) and, for link-layer protocols applicable to Space networks, the Licklider Transport Protocol Security Extensions. This document provides a security analysis of the current DTN RFCs and proposed security related internet drafts with a focus on space-based communication networks, which is a rather restricted subset of DTN networks. Note, the original focus and motivation of DTN work was for the Interplanetary Internet . This document does not address general store-and-forward network overlays, just the current work being done by the Internet Research Task Force (IRTF) and the Consultative Committee for Space Data Systems (CCSDS) Space Internetworking Services Area (SIS) - DTN working group under the DTN and Bundle umbrellas. However, much of the analysis is relevant to general store-and-forward overlays

Review on free-space optical communications for delay and disruption tolerant networks

The increase of data-rates that are provided by free-space optical (FSO) communications is essential in our data-driven society. When used in satellite and interplanetary networks, these optical links can ensure fast connections, yet they are susceptible to atmospheric disruptions and long orbital delays. The Delay and Disruption Tolerant Networking (DTN) architecture ensures a reliable connection between two end nodes, without the need for a direct connection. This can be an asset when used with FSO links, providing protocols that can handle the intermittent nature of the connection. This paper provides a review on the theoretical and state-of-the-art studies on FSO and DTN. The aim of this review is to provide motivation for the research of an optical wireless satellite network, with focus on the use of the Licklider Transmission Protocol. The assessment presented establishes the viability of these networks, providing many examples to rely on, and summarizing the most recent stage of the development of the technologies addressed.info:eu-repo/semantics/publishedVersio

Networked Operations of Hybrid Radio Optical Communications Satellites

In order to address the increasing communications needs of modern equipment in space, and to address the increasing number of objects in space, NASA is demonstrating the potential capability of optical communications for both deep space and near-Earth applications. The Integrated Radio Optical Communications (iROC) is a hybrid communications system that capitalizes on the best of both the optical and RF domains while using each technology to compensate for the other's shortcomings. Specifically, the data rates of the optical links can be higher than their RF counterparts, whereas the RF links have greater link availability. The focus of this paper is twofold: to consider the operations of one or more iROC nodes from a networking point of view, and to suggest specific areas of research to further the field. We consider the utility of Disruption Tolerant Networking (DTN) and the Virtual Mission Operation Center (VMOC) model

Performance evaluation of Licklider Transmission Protocol over Free Space Optical communication testbeds

Optical communication systems can reach transmission data rates of several Gbps but in near-Earth scenarios they are also affected by link intermittency and disruption, so that the use of the Delay-/Disruption-Tolerant Networking architecture and related protocols, such as the Licklider Transmission Protocol (LTP), seems particularly promising. For this reason, the German Aerospace Center (DLR), in accordance with Unibo, decided to devote this thesis to this topic. First, the Institute of Communication and Navigation of DLR provided us with tracks representing the dynamic state of an FSO channel between a Low Earth Orbit satellite and a ground station. Starting from these, we applied a Reed Solomon (255, 223) error correcting code and further processing to obtain “erasure vectors” (EV) representing the binary state (on/off) of the channel at a sample rate of 10 kHz. To emulate the channel in accordance with the EV traces, we developed “detemu”. Then, by using DTNperf, detemu and DTNME (the bundle protocol implementation by NASA MSFC), we performed a series of tests with LTP “red” (reliable). We developed a Python program called “LTP performance analyser” to automatically compute statistics about session durations, retransmission cycles and penalization times. Preliminary results showed that the session duration was significantly decreased by setting the retransmission time out time to 100ms instead of 1.1s, with a corresponding very significant goodput increase for a given session parallelism. We also found that by increasing the parallelism above a threshold, depending on channel characteristics and other factors, there is no advantage in terms of goodput, even if the full channel utilization is not reached, as explained in the thesis. Summarizing, LTP proved to be extremely robust to high loss ratios and an excellent match to FSO links in near-Earth scenarios

A Data Delivery Mechanism for Disconnected Mobile Applications

Previous attempts to bring the data of the internet to environments that do not have continuous connectivity to the internet have made use of special hardware which requires additional expenditure on installation. We will develop a software-based infrastructure running on existing Android smartphones to exchange application data between a disconnected user’s phone and corresponding application servers on the internet. The goal of this project is to implement client and server modules for this infrastructure to run on a disconnected phone and the internet respectively. These modules will multiplex application data to be sent into packages and distribute the data present in received packages to applications. This project will define and implement the package format and end-to-end delivery guarantees for the transmitted application data. In practice, the data will be transported physically by a mobile device like the phone of a bus driver traveling between disconnected and connected areas. Therefore, the guarantees will be based on the assumption of an opportunistic, high latency, and unreliable store-and-forward network between the client and server

Delay/Disruption Tolerant Networking Enhancements for Streaming Data

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