Delay and Disruption Tolerant Networking MACHETE Model

To verify satisfaction of communication requirements imposed by unique missions, as early as 2000, the Communications Networking Group at the Jet Propulsion Laboratory (JPL) saw the need for an environment to support interplanetary communication protocol design, validation, and characterization. JPL's Multi-mission Advanced Communications Hybrid Environment for Test and Evaluation (MACHETE), described in Simulator of Space Communication Networks (NPO-41373) NASA Tech Briefs, Vol. 29, No. 8 (August 2005), p. 44, combines various commercial, non-commercial, and in-house custom tools for simulation and performance analysis of space networks. The MACHETE environment supports orbital analysis, link budget analysis, communications network simulations, and hardware-in-the-loop testing. As NASA is expanding its Space Communications and Navigation (SCaN) capabilities to support planned and future missions, building infrastructure to maintain services and developing enabling technologies, an important and broader role is seen for MACHETE in design-phase evaluation of future SCaN architectures. To support evaluation of the developing Delay Tolerant Networking (DTN) field and its applicability for space networks, JPL developed MACHETE models for DTN Bundle Protocol (BP) and Licklider/Long-haul Transmission Protocol (LTP). DTN is an Internet Research Task Force (IRTF) architecture providing communication in and/or through highly stressed networking environments such as space exploration and battlefield networks. Stressed networking environments include those with intermittent (predictable and unknown) connectivity, large and/or variable delays, and high bit error rates. To provide its services over existing domain specific protocols, the DTN protocols reside at the application layer of the TCP/IP stack, forming a store-and-forward overlay network. The key capabilities of the Bundle Protocol include custody-based reliability, the ability to cope with intermittent connectivity, the ability to take advantage of scheduled and opportunistic connectivity, and late binding of names to addresses

CNES-NASA Disruption-Tolerant Networking (DTN) Interoperability

Future missions requiring robust internetworking services may use Delay-Disruption-Tolerant Networking (DTN) technology. CNES, NASA, and other international space agencies are committed to using CCSDS standards in their space and ground mission communications systems. The experiment described in this presentation will evaluate operations concepts, system performance, and advance technology readiness for the use of DTN protocols in conjunction with CCSDS ground systems, CCSDS data links, and CCSDS file transfer application

Applying DTN to Mobile Internet Access: a Case Study

Internetin mobiilikäyttö on yleistynyt voimakkaasti. Internet-protokollat on kuitenkin kehitetty kiinteän verkon viestintää varten ja niiden suorituskyky, erityisesti TCP:n, kärsii olosuhteissa, joissa kiinteää yhteyttä verkkoon ei ole saatavilla. EU-tutkimusprojekti nimeltä CHIANTI perustettiin tutkimaan mahdollisuutta paremman suorituskyvyn tarjoamiseksi mobiilikäyttäjille. Sen pyrkimyksenä on kehittää tietoliikenneratkaisu, jossa välityspalvelimet suojaavat käyttäjiä verkkoyhteyden katkoksilta. DTN on tietoliikennearkkitehtuuri joka on kehitetty viestinvälitykseen vaativissa olosuhteissa, esim. avaruusviestinnässä, ja mahdollistaa viestien välityksen pitkien viiveiden ja katkonaisten verkkoyhteyksien yli. Diplomityöni tarkoitus oli selvittää, voitaisiinko CHIANTI-projektin mukaiset välityspalvelimet toteuttaa hyödyntäen DTN-tutkimusryhmän kehittämää DTN-sovellusta. Työtä varten olen kehittänyt ja toteuttanut yksinkertaisen protokollan, jolla voidaan välittää HTTP-pääteyhteyksiä kahden DTN-solmun kautta. Protokollatoteutuksen avulla voidaan mitata DTN-toteutuksen suorityskykyä ja sitä kautta arvioida sen soveltuvuutta CHIANTI-projektin kannalta. Tätä varten mitattiin DTN-toteutuksen tiedonsiirtokapasiteettia sekä sen aiheuttamaa lisäviivettä HTTP-tiedostonsiirtoihin. Mittaustulokset osoittivat, että DTN-toteutus pystyy vain rajalliseen tiedonsiirtoon, suurin mitattu siirtonopeus oli vain noin 1,5 megatavua sekunnissa ja kaikissa tapauksissa DTN:n käyttö lisäsi yhteysviivettä yli 100 millisekunnilla. Tulosten valossa työssä todetaan, että tarkasteltu DTN-toteutus on hieman rajallinen suorituskyvyltään mutta silti käyttökelpoinen ja omaa potentiaalia jatkokehitykseen.Mobile use of Internet is increasing rapidly. Internet-protocols, in particular TCP, have been designed for operation with fixed connections and perform poorly in conditions of intermittent connectivity. CHIANTI is an EU-funded research project established to offer better performance for mobile Internet users. DTN is a communications architecture that has been developed to enable communications over long delays and intermittent connectivity, such as in space communications. The purpose of this work is to investigate applicability of the reference DTN implementation developed by the DTN Reseach Group to the needs and aims of CHIANTI. For this purpose I have developed a simple protocol to relay endpoint HTTP connections over a DTN link in order to be able to measure DTN performance and assess its usefulness for CHIANTI purposes. To this end, throughput capacity and delay caused by DTN are measured. Results of measurements indicate limited throughput performance of around 1.5 megabytes per second and over 100 millisecond additional delay to endpoint communications even in best cases. In light of attained results this work concludes that the DTN implementation used in this work has limited performance but could still prove useful, and has potential for further development

Geographic Centroid Routing for Vehicular Networks

A number of geolocation-based Delay Tolerant Networking (DTN) routing protocols have been shown to perform well in selected simulation and mobility scenarios. However, the suitability of these mechanisms for vehicular networks utilizing widely-available inexpensive Global Positioning System (GPS) hardware has not been evaluated. We propose a novel geolocation-based routing primitive (Centroid Routing) that is resilient to the measurement errors commonly present in low-cost GPS devices. Using this notion of Centroids, we construct two novel routing protocols and evaluate their performance with respect to positional errors as well as traditional DTN routing metrics. We show that they outperform existing approaches by a significant margin.Comment: 6 page

Survey of Inter-satellite Communication for Small Satellite Systems: Physical Layer to Network Layer View

Small satellite systems enable whole new class of missions for navigation, communications, remote sensing and scientific research for both civilian and military purposes. As individual spacecraft are limited by the size, mass and power constraints, mass-produced small satellites in large constellations or clusters could be useful in many science missions such as gravity mapping, tracking of forest fires, finding water resources, etc. Constellation of satellites provide improved spatial and temporal resolution of the target. Small satellite constellations contribute innovative applications by replacing a single asset with several very capable spacecraft which opens the door to new applications. With increasing levels of autonomy, there will be a need for remote communication networks to enable communication between spacecraft. These space based networks will need to configure and maintain dynamic routes, manage intermediate nodes, and reconfigure themselves to achieve mission objectives. Hence, inter-satellite communication is a key aspect when satellites fly in formation. In this paper, we present the various researches being conducted in the small satellite community for implementing inter-satellite communications based on the Open System Interconnection (OSI) model. This paper also reviews the various design parameters applicable to the first three layers of the OSI model, i.e., physical, data link and network layer. Based on the survey, we also present a comprehensive list of design parameters useful for achieving inter-satellite communications for multiple small satellite missions. Specific topics include proposed solutions for some of the challenges faced by small satellite systems, enabling operations using a network of small satellites, and some examples of small satellite missions involving formation flying aspects.Comment: 51 pages, 21 Figures, 11 Tables, accepted in IEEE Communications Surveys and Tutorial

Emulating opportunistic networks with KauNet Triggers

In opportunistic networks the availability of an end-to-end path is no longer required. Instead opportunistic networks may take advantage of temporary connectivity opportunities. Opportunistic networks present a demanding environment for network emulation as the traditional emulation setup, where application/transport endpoints only send and receive packets from the network following a black box approach, is no longer applicable. Opportunistic networking protocols and applications additionally need to react to the dynamics of the underlying network beyond what is conveyed through the exchange of packets. In order to support IP-level emulation evaluations of applications and protocols that react to lower layer events, we have proposed the use of emulation triggers. Emulation triggers can emulate arbitrary cross-layer feedback and can be synchronized with other emulation effects. After introducing the design and implementation of triggers in the KauNet emulator, we describe the integration of triggers with the DTN2 reference implementation and illustrate how the functionality can be used to emulate a classical DTN data-mule scenario

Routing in a many-to-one communication scenario in a realistic VDTN

In this paper, we evaluate and compare the performance of different routing protocols in a many-to-one communication within a Vehicular Delay Tolerant Network (VDTN). Seven groups with three stationary sensor nodes sense the temperature, humidity and wind speed and send these data to a stationary destination node that collect them for statistical and data analysis purposes. Vehicles moving in Tirana city roads in Albania during the opportunistic contacts will exchange the sensed data to destination node. The simulations are conducted with the Opportunistic Network Environment (ONE) simulator. For the simulations we considered two different scenarios where the distance of the source nodes from the destination is short and long. For both scenarios the effect of node density, ttl and node movement model is evaluated. 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 the increase of node density increases the delivery probability for all protocols and both scenarios, and better results are achieved when shortest-path map-based movement model is used. The increase of ttl slightly affects the performance of all protocols. By increasing the distance between source nodes and destination node, delivery probability is decreased almost 10% for all protocols, the overhead for sprayandwait protocol does not change, but for other protocols is slightly increased and the average number of hops and average latency is increased.Peer ReviewedPostprint (author's final draft

Robust streaming in delay tolerant networks

Delay Tolerant Networks (DTN) do not provide any end to end connectivity guarantee. Thus, transporting data over such networks is a tough challenge as most of Internet applications assume a form of persistent end to end connection. While research in DTN has mainly addressed the problem of routing in various mobility contexts with the aim to improve bundle delay delivery and data delivery ratio, little attention has been paid to applications. This paper investigates the support of streaming-like applications over DTN. We identify how DTN characteristics impact on the overall performances of these applications and present Tetrys, a transport layer mechanism, which enables robust streaming over DTN. Tetrys is based on an on the fly coding mechanism able to ensure full reliability without retransmission and fast in-order bundle delivery in comparison to classical erasure coding schemes. We evaluate our Tetrys prototype on real DTN connectivity traces captured from the Rollerblading tour in Paris. Simulations show that on average, Tetrys clearly outperforms all other reliability schemes in terms of bundles delivery service