Delay tolerant networking

1. Delay Tolerant Networking
Presented by,
Apoorva Hebbar

2. Overview
• Introduction
• Why DTN?
• Overview of concepts of DTN
• Conclusion

3. Today’s Internet
• Successful at interconnecting communication
devices across the globe.
• Based on TCP/IP protocol suite and wired links
• Low error rates
• Provides reliable data delivery.

4. DTN!
• Proposed solution: delay tolerant networking
architecture
• Provide a network architecture independent messaging
service.
• Operates above transport layer for various network
architectures.
• It provides store and forward functionality for dissimilar
and special networks.
• DTN required to store messages in non-volatile memory
when reliable delivery is required.
• DTN provides name-mapping via globally unique tuples.

5. Why DTN?
It provides:
–Continuous, bidirectional end-to-end path
–Short round-trips
–Symmetric data rates
–Low error rates
–Avoid irregular delays

6. Store-And-Forward Approach
 Here complete messages or a chunk of it is transferred and stored in
nodes until it reaches the destination.
 Each node is associated with a persistent storage device (like hard disk),
where it can store the messages.
– A communication link may not be available for a long time
– One node may send or receive data much faster or more reliably than
the other node
– A message, once transmitted, may need to be retransmitted if error
occurs.

7. Intermittent Connectivity
• Assume communicating devices (nodes) in
motion and/or operation with limited power
• When nodes must conserve power or
preserve secrecy, links are shut down ->
intermittent connectivity.
• On the Internet, intermittent connectivity
causes loss of data, while DTNs isolate delay
with a store-and-forward technique

8. Opportunistic Contacts
• Network nodes may need to communicate
during opportunistic contacts, in which a
sender and receiver make contact at an
unscheduled time.

9. Scheduled Contacts
• If potentially communicating nodes move along predictable paths, they
can predict or receive time schedules of their future positions and thereby
arrange their future communication sessions.
• Require time-synchronization.

10. Bundle Layer
• A Delay Tolerant Network can be considered
as an overlay on the existing regional
networks. This overlay is called as the bundle
layer,with which application programs can
communicate across multiple regions.

11. Bundle & Bundle Encapsulation
• Bundles (messages) consist of
– A source-application’s user data
– Control information, provided by the source
application for the destination application
– A bundle header, inserted by the bundle layer

12. A Non-Conversational Protocol
• DTN bundle layers communicate between
themselves using simple sessions with minimal or no
round-trips.
• Any acknowledgement from the receiving node is
optional, depending on the class of service selected.

13. DTN Nodes
• An entity with a bundle layer
– Host – sends and/or receives bundles, but does not forward them.
Optionally supports custody transfers.
– Router – forwards bundles within a single DTN region. Optionally
supports custody transfers.
– Gateway – forwards bundles between two or more DTN regions. Must
support custody transfers.

14. Delay Isolation via Transport-Layer
Termination
• DTN routers and gateways terminate transport
protocols at the bundle layer.

15. Routing Protocols
Routing in Delay Tolerant Networks can be
broadly classified into 3 types,
Dissemination based.
 Incentive based.
 History Based.

16. DTN-Region,Names &
Addresses
• A region composing a DTN, in which
communication characteristics are
homogeneous
• Has a unique region ID
Each DTN node has a two-part name,
consisting of a region ID and an entity ID
• {region id, entity id}

17. Security
• Forwarding nodes are authenticated as well as
user identities and the integrity of messages
• Sender information is authenticated by
forwarding nodes
• Both users and forwarding nodes have private
and public key-pairs and certificates

18. Conclusion• DTN is a proposed protocol standard which allows interoperability between special and challenged
networks with an easy to use API.
• Currently a hot topic, especially with NASA.
References:
• http://www.dtnrg.org/wiki
• www.ipnsig.org/reports/DTN_Tutorial11.pdf
• http://web.umr.edu/~tk424/CpE401_EE401_Spring_2006/Project/Papers-
Routing_in_DTN/Routing%20in%20a%20Delay%20Tolerant%20Networking.pdf
• http://web.umr.edu/~tk424/CpE401_EE401_Spring_2006/Project/Papers-
Routing_in_DTN/Probabilistic%20routing%20in%20intermittently%20connected%20networks.pdf
• http://web.umr.edu/~tk424/CpE401_EE401_Spring_2006/Project/Papers-
Routing_in_DTN/MobiHoc%20Poster-
Probabilistic%20routing%20in%20intermittently%20connected%20networks.pdf
• http://web.umr.edu/~tk424/CpE401_EE401_Spring_2006/Project/Papers-
Routing_in_DTN/Adaptive%20Routing%20for%20Intermittently%20Connected%20Mobile%20Ad%
20Hoc%20Networks.pdf
• http://web.umr.edu/~tk424/CpE401_EE401_Spring_2006/Project/Papers-
Routing_in_DTN/Delay%20Tolerant%20Mobile%20Networks%20(DTMNs)_%20Controlled%20Flood
ing%20Schemes%20in%20Sparse%20Mobile%20Networks.pdf
• http://web.umr.edu/~tk424/CpE401_EE401_Spring_2006/Project/Papers-
Routing_in_DTN/Knowledge%20Based%20Opportunistic%20Forwarding%20in%20Vehicular%20Wi
reless%20Ad%20Hoc%20Networks.pdf

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