Delay Tolerant Networking

Introduction to DTN:

DTN is the term for Disruption Tolerant Networking (originally stood for Delay Tolerant Networking). Sometimes it is written as Delay/Disruption Tolerant Networking. Networking once involved huge computers that took up a large room and were stationary. Now networking devices are tiny and mobile. Wikipedia has an interesting article about The History of The Internet. There is an interesting article from How Stuff Works that shows how the Internet works and the (OSI) Open Systems Interconnection Reference Model works.

In a DTN network there may be frequent Disruptions or long Delays in the connection between the network devices. Example uses for DTN are mobile computer devices: out at sea, in a cave, on a mountain, rural area, even in outer space. There will be times when these devices have a disruption in their network connection due to atmospheric conditions. For example, the delay could be to a satellite at a distant planet in space and the signal takes a few minutes to arrive. The delay could even be due to delivery by a courier of data on USB, or access to network access points on trains, buses, planes, or LEO (Low Earth Orbit) satellites to deliver the data to different parts of the network. Cisco has a router in low earth orbit called CLEO. There is even DUMBONET where elephants walk around with network access points for an emergency network in a jungle. The network needs to be able to tolerate these delays and disruptions in the connections. Since the devices are not continuously connected, data is transferred by doing a store-and-forward until the data reaches the destination. Routing is a concern in a DTN, because there may be delay in communicating to the next available path in the network.

Information on the DTN Infrastructure:

Functional Specification for DTN Infrastructure Software

DTN Primer

Interesting paper on DTN for Android devices - Delay Tolerant Network on Smartphones: Applications for Communication Challenged Areas

eLearning-DTN has a series of videos about DTN. A simple video explaining DTN is very helpful to get an idea about DTN.

N4C has Generic DTN Documentation

The InterPlanetary Networking Special Interest Group (IPNSIG) has a DTN Tutorial explain how a DTN can be used to form an Interplanetary Internet. The Interplanetary Overlay Network (ION) software distribution is an implementation of Delay-Tolerant Networking (DTN). IOAG Space Internetworking Strategy Group (SISG) & Space Internet Architecture Group (SIAG) has Information on a Recommendation on a Strategy for Space Internetworking and also Operations Concepts for a Solar System Internetwork.

The Delay-Tolerant Networking Research Group (DTNRG) lists various versions of DTN software to use. They also have lots of interesting Documents to read. DTN software is available for Debian and Ubuntu

DTN Software:

The Internet Engineering Task Force (IETF) has an interesting memo on Delay-Tolerant Networking Architecture as well as the Bundle Protocol Specification (which is the core feature of a DTN). Techopedia has an introduction to the Bundle Protocol. The Bundle Protocol (BP) can work over Transmission Control Protocol (TCP). If TCP is not used at the Transmission layer of the OSI model, then Licklider Transmission Protocol (LTP) which goes over User Datagram Protocol (UDP) is used to Transmit the Bundles. Either BP/TCP or BP/LTP/UDP is used for BP transmission.

Top Coder has a challenge from NASA - featuring various Disruption Tolerant Networking Challenges. That page also has a chart explaining the DTN stack elements.

Lawrence Goetz -