Transcript Introduction to Delay Tolerant Networks

Introduction to
Delay Tolerant Networks
Tzu-Chieh Tsai
Department of Computer Science, National Cheng Chi University
Outline
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Introduction
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How does it works?
Key Properties of DTNs
Potential Applications
Summary
Future Wireless Internet
Slide from “DTNs and Sensor Networks”, Myung-Ki Shin at Future Internet Camp, August 2007.
Introduction
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Core function of communication network
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Traditional routing solutions
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Routing
Find a path from a source to some destinations
Assume that there exists an end-to-end path between
communicating nodes
Delay/disruption tolerant networks
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Communication is possible even if end-to-end connectivity is
never achievable
Exploiting node’s mobility
Using store-carry-forward fashion
How does it work?
Traditional Routing
D
Data
S
How does it work?
Store Carry
Forward
D
Carry
S
Data
R
Forward
Store
Bagel = Source
Ants = Relay
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Fact 1: Wireless is everywhere !
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Fact 1: Wireless is everywhere !
Fact 2: We need mobility!
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Fact 1: Wireless is everywhere !
Fact 2: We need mobility!
Fact 3: Storage is cheap and vast!
Opportunistic Networks
Opportunistic Networks vs Internet
Key Properties of DTNs
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High Latency
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Low Data Rate
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Because of the disconnection.
Short Range Contact
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It is hard to find an end-to-end path.
Long Queuing Delay
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Due to the long latency of data delivery.
Disconnection
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Any two nodes may never meet each other.
Only one-hop communication is guaranteed.
Dynamic Network Topology
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Different types of user behavior will result in dramatically different
network conditions.
Outline
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Introduction
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How does it works?
Key Properties of DTNs
Potential Applications
Summary
Potential Applications
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Telemedicine for Developing Regions
DTN-based Social Network Service
Communication in the Presence of Oppressive
Governments
File Sharing and Bulk Data Transfer
Share Air Minutes
Telemedicine for Developing Regions
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Store-Carry-forward Voice-over-IP telemedicine system
Improve the possibility for doctors to give correct
diagnose and prescribe treatment from remote location
Benefit
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Can be used by those who lack computer skills.
Open source software is relatively cheap.
Can be deployed without fixed infrastructure
Challenge
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Long delay would causes some disruption in voice quality.
M. Chetty, W. Tucker, and E. Blake.
Developing locally relevant applications for rural areas: A south african example. In SAICSIT, 2004.
DTN-based Social Network Service
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DTN-based Short Message Service
Example: A farmer can send a advertisement message to
his friends, and the friends can help to propagate the
message through the social network.
Benefit
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A more convenient way to find and exchange information than
traditional face-to-face communication
Challenge
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Need to find incentive mechanisms to convince end user to
use the system
B. E. Kolko, E. J. Rose, and E. J. Johnson.
Communication as information-seeking: the case for mobile social software for developing regions. In Proc. of WWW ’07, 2007.
Communication in the Presence of
Oppressive Governments
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Anonymous Delay Tolerant Networks
Opportunistic forwarding message between people
Much more difficult for government agencies to track the
communication.
Benefit
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Using mobility and delay of transmission to increase anonymity.
Challenge
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How to avoid rogue agents injecting fake acknowledgements to
purge messages from the network?
R. Dingledine, N. Mathewson, and P. Syverson. Tor:
The second-generation onion router. In Proceedings of the 13th USENIX Security Symposium, August 2004.
File Sharing and Bulk Data Transfer
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Use the cellular network to transmit the request for
some content, and then use delay tolerant techniques to
deliver the data to the mobile device.
It’s more beneficial if the data access patterns are
somehow localized such that users in a certain area are
more likely to request a certain data item.
Benefit
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File data would rapidly be shared between a large part of
population with less resource usage.
Challenge
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Copyright and DRM issues
N. Laoutaris, G. Smaragdakis, R. Sundaram, and P. Rodriguez.
Delay-Tolerant Bulk Data Transfer on the Internet. In Proceedings of ACM SIGMETRICS 2009, Seattle, WA, June 2009.
Share Air Minutes
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Allowing the contract users to share their excess air
minutes to the prepaid card users.
The shared phone acting as the server then diverts the
voice traffic to the cellular network via the phone’s
cellular link.
Benefit
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Contract users sell their unused minutes
Pre-pay users could still use the calling service
Operators can gain the value of the resold minutes.
Challenge
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How to deal with the micro-payments?
P. Hui, R. Mortier, K. Xu, J. Crowcroft, and V. O. Li.
Sharing airtime with shair avoids wasting time and money. In Proc. of HotMobile 2009, February 2009.
Outline
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Introduction
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Research Issues
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How does it works?
Key Properties of DTNs
Mobility Pattern Analysis
Routing Protocol Design
Potential Applications
Summary
Summary
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Characteristics of DTN
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DTN routing
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No end-to-end path
Intermittent connectivity
Dynamic topology
Long delay
Flooding-based: redundancy
Forwarding-based: require topology information
Potential Application
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Urban area: DTN-based Social Network Service
Developing region: Low cost communication solutions