Contact graph routing in DTN space networks: overview, enhancements and performance

Abstract

Every mission into deep space has a communications system to carry commands and other information from Earth to a spacecraft or to a remote planet and to return scientific data to Earth [1]. Communications systems are central to the success of space missions. Large amounts of data need to be transferred (for example, nearly 25 TB in 2013 concerning the Mars Reconnaissance Orbiter (MRO)), and the demand will grow in the future [1] because of the employment of more sophisticated instruments that will generate more data. This will require the availability of high network transfer rates. Satellite systems already have to cope with difficult communication challenges: long round trip times (RTTs); the likelihood of data loss due to errors on the communication link; possible channel disruptions; and coverage issues at high latitudes and in challenging terrain. These problems are magnified in space communications characterized by huge distances among network nodes, which imply extremely long delays and intermittent connectivity. At the same time, a space communications system must be reliable over time due to the long duration of space missions. Moreover, the importance of enabling Internet-like communications with space vehicles is increasing, realizing the concept of extended Future Internet, an IP (Internet Protocol) pervasive network of networks including interplanetary communication [2], where a wide variety of science information values are acquired through sensors and transmitted.The Delay-and Disruption Tolerant Network (DTN) architecture [3] introduces an overlay protocol that interfaces with either the transport layer or lower layers. Each node of the DTN architecture can store information for a long time before forwarding it. Thanks to these features, a DTN is particularly suited to cope with the challenges imposed by space communication. As summarized in [4], the origin of the DTN concept lies in a generalization of requirements identified for interplanetary networking (IPN), where latencies that may reach the order of tens of minutes, as well as limited and highly asymmetric bandwidth, must be faced.However, other scenarios in planetary networking, called "challenged networks," such as military tactical networking, sparse sensor networks, and networking in developing or otherwise communications-challenged regions, can also benefit from the DTN solution. Delays and disruptions can be handled at each DTN hop in a path between a sender and a destination. Nodes on the path can provide the storage necessary for data in transit before forwarding it to the next node on the path. In consequence, the contemporaneous end-to-end connectivity that Transmission Control Protocol (TCP) and other standard Internet transport protocols require in order to reliably transfer application data is not required.In practice, in standard TCP/IP networks, ABSTRACTDelay-and Disruption Tolerant Networks (DTNs) are based on an overlay protocol and on the store-carry-forward paradigm. In practice, each DTN node can store information for a...

A Practical Deployment of a Communication Infrastructure to Support the Employment of Multiple Surveillance Drones Systems

“…The router is a node that is capable to relay data to other nodes. This type of node has also Delay-Tolerant capabilities [21], as it is capable to store data that should be delivered to nodes that are not immediately reachable. End-devices are generally low-power devices, such as sensor nodes, that communicate with a router or the coordinator but do not forward data.…”

Assessing Contact Graph Routing Performance and Reliability in Distributed Satellite Constellations

“…Although a complex and extensive algorithm, CGR is considered to be among the most mature strategies towards 8 Journal of Computer Networks and Communications forwarding and routing in space DTNs [30]. To the best of authors' knowledge, this section constitutes one of the most detailed overviews of the algorithm in the literature as of today.…”

“…During the last decade, the DTN Bundle protocol, along with different adaptation layers, has been proposed [14][15][16][17][18][19], several routing strategies were studied [20][21][22][23][24][25][26][27][28][29][30], and diverse software stacks were publicly released [31][32][33][34][35]. Furthermore, some of the latter approaches were successfully validated both on LEO [36] and Deep Space missions [37] driven by the UK Space Agency and NASA, respectively.…”

“…An initial performance comparison of these topologies is one of the contributions of this work. For the reliability analysis, the state-of-the-art version of Contact Graph Routing (CGR) algorithm was considered [30]. However, to the best of the authors' knowledge, there is a lack of an in-depth description of the latest CGR algorithm which is only available as part of an open-source DTN implementation [32].…”

A Novel DTN Routing Algorithm in the GEO-Relaying Satellite Network

“…Many routing algorithms evaluate the performance of route by its hop count and transmission delivery time [11] [12] . However it does not consider the link reliability.…”