Delay/Disruption-Tolerant Network

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DNR
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Delay/Disruption-Tolerant Network

Post by DNR »

As a part of my studies in to SIPRNET, RIPRNET, WiFi, and just plain old TCP/IP, I have included this short tut on DTN,another network protocol.

DTN

Delay/Disruption-Tolerant Network Testing Using a LEO Satellite
http://esto.nasa.gov/conferences/estc20 ... m_A4P2.pdf
or
http://esto.gsfc.nasa.gov/conferences/e ... icA4P2.pdf

This paper describes the first DTN bundle protocol testing from space, using the United Kingdom Disaster Monitoring Constellation (UK-DMC) satellite in Low
Earth Orbit (LEO). The mismatch problems between the different conditions of the private dedicated space-to-ground link and the shared, congested, ground-to-ground links are discussed. DTN, with its ability to transfer files on a hop-by-hop basis across
different subnets, is presented as a technology that can be used to alleviate this problem.

Delay/Disruption Tolerant Networking (DTN) has been
defined as an end-to-end store-and-forward architecture
capable of providing communications in highly-stressed
network environments. To provide the store-and-forward
service, a “bundle” protocol (BP) sits at the application layer of
some number of constituent internets, forming a store-andforward
overlay network [1]. Key capabilities of the BP
include:
• Custody-based retransmission – the ability to take
responsibility for a bundle reaching its final destination
• Ability to cope with intermittent connectivity.
• Ability to cope with long propagation delays.
• Ability to take advantage of scheduled, predicted, and
opportunistic connectivity (in addition to continuous
connectivity).
• Late binding of overlay network endpoint identifiers to
constituent internet addresses

The UK-DMC satellite’s onboard payloads include:
• The Cisco router in Low Earth Orbit (CLEO). CLEO
has been used for network testing and is its own
experiment to simply show that a commercial-off-theshelf
router could survive and function in orbit. CLEO
is not used for DTN bundle testing.

one SSDR(Solid-State Data Recorders) based around a StrongARM
Processor,with Motorola MPC8260 PowerPC
processors is used for DTN testing.
These run the RTEMS operating system, which
supports the POSIX API and BSD sockets.
These have a constrained operating system
firmware size limit of 1 MByte, and storage
capacities of 1 GByte and 512MByte RAM

There is an uplink of 9600 bits per second, and
downlink of 8.134 Mbps – this is highly asymmetric.
Both links use the proven IPv4/Frame Relay/HDLC
encapsulation developed for space by Keith Hogie .
IPv6 has been tested over these links, using the
onboard CLEO router (the off-the-shelf cisco router!)
The IP-based transport protocol used for downloading images is SSTL’s
original implementation of Saratoga, running over UDP.

the DTN-bundle-receiving intelligence only needed to
be present in the ground station implementation of the
Saratoga client and the DTN bundle agent. The Saratoga
client in the ground station queries the UK-DMC satellite for a
directory of files, and then requests any files with a “.dtn”
extension and an associated satellite image file. (File naming
conventions are discussed in detail later.) The satellite image
file and associated metadata files are transferred to the ground,
where the Saratoga client reassembles the bundles and then
presents them to the full DTN bundle agent

All network layer communications used IPv4, with the simulated
space/ground data link implemented using Frame Relay/HDLC.

Reliability, error detection, and checksums
The current Bundle Protocol specification does not address
reliability, in that it has no checksum support for error
detection and rejection of corrupted bundles. That means that
one cannot determine if the bundle information received at
each hop was received error-free. Error detection is a very
basic networking concept that was overlooked in the bundle
protocol design. The current proposed workaround is to use the
bundle security specification and to wrap the bundle using a
reliability-only cipher rather than a security cipher that
provides a reliability check as a side-effect of security [13].
However, the bundle security specification was not
implemented here. Thus, there were no reliability checks. If
checksums had been implemented as part of the core DTN
bundle specification, the “holes to fill” implementation
problem would have been discovered early on, and corrupt
bundles would not have been transferred through our entire
DTN network. (remember, this is not TCP/IP protocol anymore)

synchronization problem was experienced during initial
ground testing. All DTN bundle agents were originally
configured and tested at NASA GRC in Cleveland, Ohio. One
bundle agent was sent to Guildford, England. A second was
sent to Universal Space Networks (USN) in Alaska. When
performing initial DTN bundle transfers from SSTL to GRC to
USN, it was noted that the machine clocks had drifted
sufficiently enough to result in the bundle time stamps being
out of synchronization. The DTN bundles were therefore
rejected due to time-stamp mismatch.

The lack of integrity checksums in the Bundle Protocol and
the need for DTN network synchronization have shown to be
real deployment issues during our initial tests.

---EOF---

Content-Based Networking:
DTN, AMS, Sharednet
http://trs-new.jpl.nasa.gov/dspace/bits ... 6-2684.pdf

DARPA DTN
Phase 2 Kickoff
Arlington, VA
9 August 2006
Scott Burleigh
Systems Engineering Section
Jet Propulsion Laboratory, California Institute of Technology

DARPA Content-Based Networking
Summary of Requirements
1. Want to push data, so that it’s there as soon as it’s needed.
• Minimize latency.
2. But don’t want to push everything to everybody; targets must pull
what they need.
• Minimize bandwidth consumption.
3. Must retain data until user is ready to use it, and not decrypt until
then.
• Minimize need for repeated transmission.
• Minimize security exposure.

Concept
• For secure data retention within the network fabric:
DTN Bundle Protocol (BP).
• To strike a balance between data “push” and “pull”:
AMS publish/subscribe functionality.
• For secure data cache at the edge of the network:
Sharednet relevant common operational picture.
• Sharednet client registers as an AMS node.
– Uses AMS to subscribe on user’s behalf.
– Receives remotely published data via Remote AMS (RAMS) gateway.
– Caches data locally, securely, pending retrieval by the user.
• Messages are exchanged among RAMS gateways via Bundle
Protocol, over whatever underlying transport is available.

Middleware developed by JPL for the US Navy and Marine Corps
• Objective:
– Distribute the C2 information needed to assemble a relevant common
operational picture (COP).
– Provide the distribution framework required to facilitate collaborative planning
and increased situational awareness (i.e. storage, translators, and agents).

Cross platform interoperability must be supported.
• Java & C++ clients
• Linux, Mac OS, Solaris, Windows

– DTN retains data at routers while waiting for links.
– Sharednet retains data at edge nodes while waiting for queries.

--- EOF ---

NASA Tests First Deep-Space Internet
http://www.jpl.nasa.gov/news/news.cfm?release=2008-216

Unlike TCP/IP on Earth, the DTN does not assume a continuous end-to-end connection. In its design, if a destination path can't be found, the data packets are not discarded. Instead, each network node keeps custody of the information as long as necessary until it can safely communicate with another node. This store-and-forward method, similar to basketball players safely passing the ball to the player nearest the basket, means that information does not get lost when no immediate path to the destination exists. Eventually, the information is delivered to the end user.

---EOF---
Delay Tolerant Networks, a tutorial
http://www.ipnsig.org/reports/DTN_Tutorial11.pdf

---

http://www.hq.nasa.gov/office/hqlibrary ... adoc.htm#D

---

NASA Tests First Deep-Space Internet
http://www.nasa.gov/topics/technology/f ... 81118.html

NASA and Vint Cerf, a vice president at Google, Inc., in Mountain View, Calif., partnered 10 years ago to develop this software protocol. The DTN sends information using a method that differs from the normal Internet's Transmission-Control Protocol/Internet Protocol, or TCP/IP communication suite, which Cerf co-designed.

---

OTHER
Mixmaster Protocol Version 2
http://www.abditum.com/mixmaster-spec.txt

Mixmaster is based on D. Chaum's mix-net protocol.
A mix (remailer) is a service that forwards messages, using public key
cryptography to hide the correlation between its inputs and outputs.
Sending messages through sequences of remailers achieves anonymity and
unobservability of communications against a powerful adversary

Message transmission can be protected against traffic analysis by the
mix-net protocol. A mix (remailer) is a service that forwards
messages, using public key cryptography to hide the correlation
between its inputs and outputs.

The mix-net protocol [Chaum 1981] allows one to send messages while hiding
the relation of sender and recipient from observers
(unobservability). It also provides the sender of a message with the
ability to remain anonymous to the recipient

Only the last remailer in the chain can determine whether packets are
part of a certain message. To all the others, they are completely
independent

In order to obfuscate the link between incoming and outgoing messages,
Mixmaster uses a pooling scheme. Messages that are to be forwarded
anonymously are stored in a pool. In regular intervals the remailer fires
and sends some random messages from the pool to either the next hop or
their final recipients

Every time a message is placed in the pool, the remailer chooses a random
number from a geometric distribution and creates that many dummy messages
which are also placed in the pool.

Similarly, prior to each execution of the mixing algorithm described in
section 3.1, the remailer selects a random number from a different geometric
distribution and adds that many dummy messages to the pool as well.

--EOF---


DNR
-
He gives wisdom to the wise and knowledge to the discerning. He reveals deep and hidden things; he knows what lies in Darkness, and Light dwells with him.

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