Delay Tolerant Networking

From Wikipedia, the free encyclopedia

Delay-Tolerant Networking (DTN) is an approach to computer network architecture that seeks to address the technical issues in mobile or extreme environments that lack continuous network connectivity.

Recently, Disruption-Tolerant Networking has become a favorable term since it applies to more situations, and this term has gained currency in the United States military and DARPA, who have funded many DTN projects. Disruption may occur because of the limits of wireless radio range, sparsity of mobile nodes, energy resources, attack, and noise.

Contents

[edit] History

Further information: History of delay tolerant networking

In the 1970s, spurred by the micronization of computing, researchers began developing technology for routing between non-fixed locations of computers. While the field of ad-hoc routing was inactive throughout the 1980s, the wide-spread use of wireless protocols reinvigorated the field in the 1990s as mobile ad-hoc routing and vehicular ad-hoc networking became areas of increasing interest.

With the growing interest in mobile ad-hoc routing and the proposal of the Interplanetary Internet by Vint Cerf, relating to the necessity of networking technologies that can cope with the significant delays and packet corruption of deep-space communications, the 2000s brought about increased interest in DTNs, including a growing number of academic conferences on delay and disruption tolerant networking. This field saw many optimizations on classic ad-hoc and delay-tolerant networking algorithms and began to examine factors such as security, reliability, verifiability, and other areas of research that are well understood in traditional computer networking.

[edit] Routing

Further information: Routing in delay tolerant networking

The ability to transport, or route, data from a source to a destination is a fundamental ability all communication networks must have. Delay and disruption-tolerant networks (DTNs), are characterized by their lack of connectivity, resulting in a lack of instantaneous end-to-end paths. In these challenging environments, popular ad hoc routing protocols such as AODV[1] and DSR[2] fail to establish routes. This is due to these protocols trying to first establish a complete route and then, after the route has been established, forward the actual data. However, when instantaneous end-to-end paths are difficult or impossible to establish, routing protocols must take to a "store and forward" approach, where data is incrementally moved and stored throughout the network in hopes that it will eventually reach its destination[3][4][5]. A common technique used to maximize the probability of a message is successfully transfered is to replicate many copies of the message in hopes that one will succeed in reaching its destination[6].

[edit] Other concerns

[edit] Bundle Protocols

In efforts to provide a shared framework for algorithm and application development in DTNs, RFC 4838 and RFC 5050 were published in 2007 to define a common abstraction to software running on disrupted networks. Commonly known as the Bundle Protocol, this protocol defines a series of contiguous data blocks as a bundle -- where each bundle contains enough semantic information to allow the application to make progress where an individual block may not. Bundles are routed in a store and forward manner between participating nodes over varied network transport technologies (including both IP and non-IP based transports). The transport layers carrying the bundles across their local networks are called bundle convergence layers. The bundle architecture therefore operates as an overlay network, providing a new naming architecture based on Endpoint Identifiers (EIDs) and coarse-grained class of service offerings.

Protocols using bundling must leverage application-level preferences for sending bundles across a network. Due to the store and forward nature of delay-tolerant protocols, routing solutions for delay tolerant networks can benefit from exposure to application-layer information. For example, network scheduling can be influenced if application data must be received in its entirety, quickly, or without variation in packet delay. Bundle protocols collect application data into bundles that can be sent across heterogeneous network configurations with high-level service guarantees. The service guarantees are generally set by the application level, and the RFC 5050 Bundle Protocol specification includes 'bulk', 'normal', and 'expedited' markings.

[edit] Security

Addressing security issues has been a major focus of the bundle protocol.

Security concerns for delay-tolerant networks vary depending on the environment and application, though authentication and privacy are often critical. These security guarantees are difficult to establish in a network without persistent connectivity because the network hinders complicated cryptographic protocols, hinders key exchange, and each device must identify other intermittently-visible devices.[7][8] Solutions have typically been modified from mobile ad hoc network and distributed security research, such as the use of distributed certificate authorities and PKI schemes. Original solutions from the delay tolerant research community include the use of identity-based encryption, which allows nodes to receive information encrypted with their public identifier. [9]

[edit] Research efforts

Various research efforts are currently investigating the issues involved with DTN:

[edit] Footnotes

  1. ^ Perkins, C. & Royer, E. (1999), “Ad-hoc on-demand distance vector routing”, The Second IEEE Workshop on Mobile Computing Systems and Applications 
  2. ^ Johnson, D. & Maltz, D. (1996), “Dynamic source routing in ad hoc wireless networks”, Mobile Computing, Kluwer Academic, pp. 153 - 181 
  3. ^ John Burgess, Brian Gallagher, David Jensen, and Brian Neil Levine. MaxProp: Routing for vehicle-based disruption-tolerant networks. In Proc. IEEE INFOCOM, April 2006.
  4. ^ Philo Juang, Hidekazu Oki, Yong Wang, Margaret Martonosi, Li Shiuan Peh, and Daniel Rubenstein. Energy-efficient computing for wildlife tracking: design tradeoffs and early experiences with zebranet. SIGOPS Oper. Syst. Rev., 36(5):96–107, 2002.
  5. ^ Augustin Chaintreau, Pan Hui, Jon Crowcroft, Christophe Diot, Richard Gass, and James Scott. Impact of human mobility on opportunistic forwarding algorithms. IEEE Transactions on Mobile Computing, 6(6):606–620, 2007.
  6. ^ Vahdat, Amin & Becker, David (2000), “Epidemic routing for partially connected ad hoc networks”, Technical Report CS-2000-06, Duke University 
  7. ^ "Anonymity and security in delay tolerant networks" A. Kate, G. Zaverucha, and U. Hengartner. 3rd International Conference on Security and Privacy in Communication Networks (SecureComm 2007)
  8. ^ "Security Considerations in Space and Delay Tolerant Networks" S. Farrell and V. Cahill. Proceedings of the 2nd IEEE International Conference on Space Mission Challenges for Information Technology
  9. ^ "Practical security for disconnected nodes" Seth, A. Keshav, S. 1st IEEE ICNP Workshop on Secure Network Protocols (NPSec), 2005.