29-06-2012, 03:43 PM
Delay- and Disruption- Tolerant Networking
[attachment=26145]
Many important Internet transport protocols
fail in environments without contemporaneous
end-to-end connectivity.
Here, we review the delay- and disruptiontolerant
networking (DTN) approach to dealing
with this problem, with an emphasis on the
“prestandards” work of the Internet Research
Task Force’s (IRTF) Delay-Tolerant Networking
Research Group (DTNRG; www.dtnrg.org).
The Birth of DTN
During 2001 and 2002, IPN researchers investigated
how they could apply the IPN architecture
Alex McMahon and Stephen Farrell • Trinity College Dublin
Delay- and disruption-tolerant networking (DTN) grew out of attempts to
develop an Interplanetary Internet but has evolved into an active area of
networking research, with applications in space networking, military tactical
networking, and networking for various challenged communities. The DTN
Research Group provides an open forum in which DTN researchers and
developers can collaborate to further develop this experimental technology.
NOVEMBER/DECEMBER 2009 83
Delay- and Disruption-Tolerant Networking
to other situations in which communications
were subject to delays
and disruptions. In August 2002, the
IPNRG published an updated version
of the draft as “Delay-Tolerant
Network Architecture: The Evolving
Interplanetary Internet” (see www.
ietfid/draft-irtf-ipnrg-arch-01.
The Bundle Protocol
BP was specifically developed conformant
to the DTN architecture.
It essentially runs at the application
layer and generally follows the
overlay-network approach. Although
BP can run over TCP/IP, it can also
run over other, lower-layer protocols
(so-called convergence layers)
— for example, proprietary protocols
deployed in sensor networks or, for
deep-space deployments, LTP. BP’s
key capabilities include custodybased
retransmission; an ability to
cope with intermittent connectivity;
an ability to take advantage of
scheduled, predicted, and opportunistic
connectivity (in addition to
continuous connectivity); and late
binding of overlay network endpoint
identifiers (EIDs) to convergence
layer-specific addresses, such
as IP addresses. Devices implementing
BP are called DTN nodes.
Bundles and Fragments
Bundles contain a primary block and
one or more other blocks of data.
The primary block contains basic
information, such as the destination
EID, which is required for bundle
routing and forwarding. Each
block can contain either application
data or other information used to
deliver the containing bundle to its
destination. Blocks hold information
typically found in the header
or payload portion of protocol
data units in other protocol architectures.
DTN Adoption
Several wireless sensor networks
have deployed DTN, and many other
DTN deployments are described
elsewhere,12 including using DTN
for underwater acoustic networking,
meteorological and animal
tracking, and various other sensor
networks. Since 2003, DARPA has
had a DTN program with the aim to
develop and field network services
that deliver critical information
reliably even when no end-to-end
path exists through the network.
DARPA based phases one and two
of its program on the Spindle (Survivable
Policy-Influenced
Networking:
[attachment=26145]
Many important Internet transport protocols
fail in environments without contemporaneous
end-to-end connectivity.
Here, we review the delay- and disruptiontolerant
networking (DTN) approach to dealing
with this problem, with an emphasis on the
“prestandards” work of the Internet Research
Task Force’s (IRTF) Delay-Tolerant Networking
Research Group (DTNRG; www.dtnrg.org).
The Birth of DTN
During 2001 and 2002, IPN researchers investigated
how they could apply the IPN architecture
Alex McMahon and Stephen Farrell • Trinity College Dublin
Delay- and disruption-tolerant networking (DTN) grew out of attempts to
develop an Interplanetary Internet but has evolved into an active area of
networking research, with applications in space networking, military tactical
networking, and networking for various challenged communities. The DTN
Research Group provides an open forum in which DTN researchers and
developers can collaborate to further develop this experimental technology.
NOVEMBER/DECEMBER 2009 83
Delay- and Disruption-Tolerant Networking
to other situations in which communications
were subject to delays
and disruptions. In August 2002, the
IPNRG published an updated version
of the draft as “Delay-Tolerant
Network Architecture: The Evolving
Interplanetary Internet” (see www.
ietfid/draft-irtf-ipnrg-arch-01.
The Bundle Protocol
BP was specifically developed conformant
to the DTN architecture.
It essentially runs at the application
layer and generally follows the
overlay-network approach. Although
BP can run over TCP/IP, it can also
run over other, lower-layer protocols
(so-called convergence layers)
— for example, proprietary protocols
deployed in sensor networks or, for
deep-space deployments, LTP. BP’s
key capabilities include custodybased
retransmission; an ability to
cope with intermittent connectivity;
an ability to take advantage of
scheduled, predicted, and opportunistic
connectivity (in addition to
continuous connectivity); and late
binding of overlay network endpoint
identifiers (EIDs) to convergence
layer-specific addresses, such
as IP addresses. Devices implementing
BP are called DTN nodes.
Bundles and Fragments
Bundles contain a primary block and
one or more other blocks of data.
The primary block contains basic
information, such as the destination
EID, which is required for bundle
routing and forwarding. Each
block can contain either application
data or other information used to
deliver the containing bundle to its
destination. Blocks hold information
typically found in the header
or payload portion of protocol
data units in other protocol architectures.
DTN Adoption
Several wireless sensor networks
have deployed DTN, and many other
DTN deployments are described
elsewhere,12 including using DTN
for underwater acoustic networking,
meteorological and animal
tracking, and various other sensor
networks. Since 2003, DARPA has
had a DTN program with the aim to
develop and field network services
that deliver critical information
reliably even when no end-to-end
path exists through the network.
DARPA based phases one and two
of its program on the Spindle (Survivable
Policy-Influenced
Networking: