NASA’s Disruption Tolerant Networking Challenge Series

Welcome to the NASA Disruption Tolerant Networking (DTN) project. DTN is an approach to computer network architecture that seeks to address the technical issues in heterogeneous networks that may lack continuous network connectivity. Examples of such networks are those operating in mobile or extreme terrestrial environments, or planned networks in space. Disruption may occur because of the limits of wireless radio range, sparsity of mobile nodes, energy resources, attack, and noise.

DTN Interactive Stack Elements

Click or mouseover any of the blocks below for more details.

USER APPLICATION
An unlimited variety of user applications can utilize network service based on DTN. The only constraint is that the application must itself be tolerant of potentially long latencies in round-trip communications. Applications that distribute information as soon as it is known - without waiting for queries - and that can act on information they already have in hand - without waiting for responses to queries - are likely to be most successful in a DTN environment. Publish/subscribe architectures are highly delay-tolerant; client/server architectures are usually not.
File Transfer
A delay-tolerant file transfer protocol has been standardized by the Consultative Committee for Space Data Systems (CCSDS): it's named 'CCSDS File Delivery Protocol' (CFDP). The details of the protocol are provided in CCSDS document 727.0-B-4.
DTPC (Delay-Tolerant Payload Conditioning)
Delay-Tolerant Payload Conditioning (DTPC) is a new DTN application service that is currently being standardized within the Consultative Committee for Space Data Systems (CCSDS). It performs several functions that need to be executed only at the original source and final destination of an end-to-end network path, rather than at the intermediate forwarders: user data aggregation and elision, end-to-end acknowledgment and retransmission, and data sequencing and gap detection. In some ways it's analogous to TCP, the Internet's Transmission Control Protocol.
Bundle Protocol (Intra-DTN Routing)
The Bundle Protocol (BP) is the core 'network protocol' of Delay-Tolerant Networking. It is analogous to IP, the Internet Protocol, but with some key differences: outbound data items ('bundles') are retained in local storage, rather than discarded, when the link to the next node in the end-to-end path is suspended, and the 'time to live' of a bundle is measured in seconds rather than in network 'hops'. The details of the protocol are provided in Internet RFC 5050.
LTP (Retransmission)
Licklider Transmission Protocol (LTP) is an ARQ [Automatic Repeat-reQuest] system that ensures the delivery of bundles from one DTN node to another even if link service is intermittently suspended for hours or days and/or the nodes are separated by minutes or hours of signal propagation delay. The details of the protocol are provided in Internet RFCs 5325, 5326, and 5327.
UDP
LTP provides generalized delay-tolerant retransmission service between two DTN nodes - it's not limited to any single type of network link. For research and demonstration of LTP on Earth the most convenient underlying link service is UDP/IP.
TCP (Retransmission)
DTN is designed to let a single end-to-end data exchange span all kinds of network environments, ranging from space links with signal propagation times measured in minutes to reliable Internet connections with round-trip latencies measured in milliseconds. For DTN communications over path segments served by the Internet, TCP is an excellent 'convergence layer' choice.
IP (Intra-Internet Routing)
Ethernet, Wi-Fi, FDDI
Wire, Fiber, R/F
Application Layer
Transport Layer
Network Layer
Physical Layer

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