Delay/Disruption Tolerant Networks

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Delay/Disruption Tolerant Networks

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Todays Internet

• interconnecting communication devices across the
  globe.
• using a homogeneous set of communication
  protocols, called TCP/IP.
• connectivity relies primarily on wired links.

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Evolving Wireless Networks Outside the Internet

• terrestrial civilian networks connecting mobile
  wireless devices including personal
  communicators, intelligent highways, and sensors.
• wireless military battlefield networks connecting
  troops, aircraft and satellites.
• outer-space networks

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Concept of a DTN

• A DTN is a network of regional networks.
• It is an overlay on top of regional networks,
  including the Internet.
• Characteristics
• intermittent connectivity
• long or variable delay
• asymmetric data rates
• high error rates

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DTN Examples
                                                
 

• ZebraNet at Princeton
• DakNet at MIT
• DiselNet at UMass

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Challenges

• Link layer
• Network layer
• Transport layer
• Application layer

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Link Layer

• Network heterogeneity
• Intermittent connectivity -gt Discovery problem

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Network Layer

• Addressing
• Routing and mobility
• Buffer management

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Transport Layer

• Arbitrary delay
• Non-conversational protocol
• Reliability

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DTN Routing

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Categories

• Deterministic
• Stochastic

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Deterministic Routing

• Routing in a delay tolerant network by S. Jain,
  K. Fall and R. Patra, Sigcomm 2004.

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Traffic Carried by Contact Type
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Delay Comparison
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DTN with City Buses
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Results
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Epidemic Routing

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Partially-Connected Ad Hoc Networks

• Mobile Sensor Networks
• Smart Dust
• Disaster Recovery/Military Deployment

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Goals

• Efficiently distribute messages through partially
  connected ad hoc networks in a probabilistic
  fashion
• minimize the amount of resources consumed in
  delivering any single message
• maximize the percentage of messages that are
  eventually delivered to their destination

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Issues

• Routing under uncertainty
• Resource allocation
• Performance latency, storage, communication
  cost, and energy consumption
• Reliability
• Security

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An Epidemic Routing Protocol

• 32 bit message id
• source IP local message ID
• Hop count
• the maximum number of epidemic exchanges

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Performance - Scenario

• 50 mobile nodes in 1500m by 300m
• Speed 0 to 20 m/sec.
• Message length 1 KB
• Traffic
• 45 nodes send one message to other 44 nodes.
• Total 45 44 1980.
• Each message is initiated every second.
• Buffer size 2000 packets
• Drop policy FIFO

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Delivery Rate with Infinite TTL
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Summary
with DSR
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Delivery Rate with Hop Limit
with 50 meter transmission range
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Delivery Rate with Buffer Limit
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Enhancement with Next Hop Info.

• Drop Random
• Drop Least Recently Received
• Drop Oldest
• Drop Least Encountered

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Performance