| Delay
Tolerant Networking |
Introduction
Increasingly,
network applications must communicate with counterparts across disparate networking
environments characterized by significantly different sets of physical and operational
constraints; wide variations in transmission latency are particularly troublesome.
The proposed Interplanetary Internet, which must encompass both terrestrial and
interplanetary links, is an extreme case. An architecture based on a "least
common denominator" protocol that can operate successfully and (where required)
reliably in multiple disparate environments would simplify the development and
deployment of such applications. The highly successful architecture and supporting
protocols of today's Internet are ill suited for this purpose. But Delay Tolerant
Networking will crossover this bottle-neck. In this seminar the fundamental principles
that would underlie a delay-tolerant networking (DTN) architecture and the main
structural elements of that architecture, centered on a new end-to-end overlay
network protocol called Bundling is examined. The
US Defense Advanced Research Projects Agency (DARPA), as part of its "Next
Generation Internet" initiative, has recently been supporting a small group
at the Jet Propulsion Laboratory (JPL) in Pasadena, California to study the technical
architecture of an "Interplanetary Internet". The idea was to blend
ongoing work in standardized space communications capabilities with state of the
art techniques being developed within the terrestrial Internet community, with
a goal of facilitating a transition as the Earth's Internet moves off-planet.
The "Interplanetary Internet" name was deliberately coined to suggest
a far-future integration of space and terrestrial
communications infrastructure
to support the migration of human intelligence throughout the Solar System. Joining
the JPL team in this work was one of the original designers of the Internet and
co-inventor of the "Transmission Control Protocol/Internet Protocol"
(TCP/IP) protocol suite. Support for the work has recently transitioned from DARPA
to NASA.
An architecture based on a "least
common denominator " protocol that can operate successfully and reliably
in multiple disparate environments would simplify the development and deployment
of Interplanetary Internet. It is this analysis that lead to the proposal of Delay-Tolerant
Network (DTN) architecture, an architecture that can support deep space applications,
centered on a new end-to-end overlay network protocol called 'Bundling'. The architecture
and protocols developed for the project could also be useful in terrestrial environments
where the dependence on real time interactive communication is not possible. The
Internet protocols are ill suited for this purpose, while the overlay protocol
used in DTN architecture serves to bridge between different stacks at the boundaries
between environments in a standard manner, in effect providing a general -purpose
application-level gateway infrastructure that can be used by any number of applications.
DTN is an architecture based on Internet-independent middleware: use exactly those
protocols at all layers that are best suited to operation within each environment,
but insert a new overlay network protocol between the applications and the locally
optimized stacks.
Research on extending
Earth's Internet into interplanetary space has been underway for several years
as part of an international communications standardization body known as the Consultative
Committee for Space Data Systems (CCSDS). CCSDS is primarily concerned with communications
standards for scientific satellites, with a focus more on the needs of near-term
missions. To extend this horizon into the future, and to involve the terrestrial
internet research and engineering communities, a special Interplanetary Internet
study was proposed and subsequently sponsored in the United States by NASA's Jet
Propulsion Laboratory (JPL) and DARPA's Next Generation Internet Initiative
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