Download - DELAY-TOLERANT NETWORKS Volodymyr Goncharov Freiburg Uni, WS 2009, Seminar Ad Hoc Netzwerke
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DELAY-TOLERANTNETWORKS
Volodymyr GoncharovFreiburg Uni, WS 2009, Seminar Ad Hoc Netzwerke
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Copyright Notice
Content of this presentation is based on the papers [1], [2]
Images were mostly taken from [2]
[1] RFC4838 2007 Delay-Tolerant Networking Architecture
[2] Warthman, F. 2003 Tutorial. Delay-Tolerant Networks (DTNs)
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Outline
Introduction Concept Internet vs. DTN Features
Protocol and architecture details Challenged networks Evaluation of DTN
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Concept
Delay-Tolerant Network (DTN) is an overlay on top of regional networks
built on top of region-specific lower layers messages are called bundles
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Concept
Delay-Tolerant Network (DTN) is a network of regional networks
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Concept
Delay-Tolerant Network (DTN) was originally designed to support the
InterPlanetary Internet (IPN)
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Internet vs. DTN
Internet is mainly based on packet switching nodes are continuously connected IP protocol is used on the network layer excessive network traffic in case of errors
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Internet vs. DTN
DTN uses the store-and-forwarding method messages might be sent to unavailable end
hosts hop-to-hop retransmission in case of errors
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Internet vs. DTN
DTN isn’t necessarily built on top of TCP/IP
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Internet vs. DTN
Communication on the Internet is mainly based on packet switching
DTNs use store-and-forward message switching very similar to the way email systems work
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Features
Intermittent connectivity Opportunistic contacts Scheduled contacts
Non-conversational protocol Security
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Outline
Introduction Protocol and architecture details
Types of nodes Node names Addressing Security
Challenged networks Evaluation of DTN
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Types of nodes13
Host Router
works within a single DTN region Gateway
connects neighboring networks
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Node names14
based on URIs consist of region and entity ids
Example:dnt://earth.sol.int/src.someclient.com
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Addressing15
unicast dnt://earth.sol.int/src.someclient.com
anycast dnt://earth.sol.int/*.someclient.*
multicast dnt://earth.sol.int/*.someclient.*
broadcast dnt://earth.sol.int/*
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Security16
Network routers participate in authentication
Private and public certificates are used Each message contains a “postage
stamp” keeping a signature of the sending node
A new signature is generated every time the message arrives to the next node
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Outline
Introduction Protocol and architecture details Challenged networks Evaluation of DTN
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Challenged networks18
Terrestrial Mobile Networks may easily become partitioned
Exotic Media Networks longs delays and connection interruptions communication with submarines or low-
earth orbiting satellites, deep space RF communication
Sensor-based Networks scheduled communications to save power
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Outline
Introduction Protocol and architecture details Challenged networks Evaluation of DTN
Test 1 Test 2 Test 3
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Evaluation of DTN20
In the paper “Implementing Delay Tolerant Networking”, authors created and evaluated a DTN network
Tests were run on end-to-end and hop-by-hop configurations
DTN, Mail and SFTP protocols
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Test 121
No disconnections
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Test 222
Periodic disconnectivity of each node Disruptions are cyclical Links are up for one minute, then down
for three Message sizes are 40K
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Test 223
4 types of disruptions: aligned shift (10 sec.) sequential random
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Test 224
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Test 325
10 sec. phase shift scenario 200 KB messages pro-active fragmentation in DTN
into smaller 40KB bundles
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Test 326
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Questions and Discussion27