DTNsDelay Tolerant Networks

• Fall, Kevin. Intel Research, Berkeley. SIGCOMM 2003 Aug25, 2003. A Delay-Tolerant Network Architecture for Challenged Internets. August 2003.

• Warthman, Forrest. Delay Tolerant Networks (DTNs): A Tutorial. March 2003.

• Jones, Evan P.C. Practical Routing in Delay-Tolerant Networks.

Papers

• TCP/IP service model works great with connected, reliable networks.

• Several implicit assumptions:– E2E Path exists (Connected)– RTT small– Drop probability is small– Symmetric Data Rates

Introduction

The TCP/IP Model

The TCP/IP Model

• Terrestrial Mobile Networks• Exotic Media Networks• Military Ad Hoc Networks• Sensor Networks

Challenged Networks

Terrestrial Mobile Network Example

Path and Link Characteristics• High Latency• Low Data Rate• Disconnection• Long Queuing Times

Challenged Networks

End System Characteristics• Limited Longevity• Low Duty Cycle Operation• Limited Resources

Challenged Networks

Fix TCP/IP?Link Repair Approach

Performance Enhancing Proxy (PEP)Protocol Boosters

Proxies

Electronic MailUS Postal Service

Message Based Overlay ArchitectureBundling

Ideas

Store and Forward

Nodes use persistent storage to store messages indefinitely

Forward when able to do so,Otherwise, wait

DTN

DTN Regions

A DTN is a network of networksThese “sub” networks are called RegionsEach Region has a unique Region ID that is

globally known throughout the DTNDTN Resources are identified by name tuples

(Region ID, Entity ID)DTN Gateways are members of two or more

regions and handles all communication between regions

Overlay: The Bundle Layer

Overlay: The Bundle Layer

DTN Nodes

Custody Transfers

Hosts store bundles in persistent storage until custody can be passed or TTL expires

Hosts request custody transfer to next-hop nodeNext-hop node has option to accept custodyLocal copy removed upon transfer of custodyOnly nodes supporting CT can accept custodyTransport Layer protocol terminates upon

acceptance of custody

Custody Transfers

Overlay: The Bundle Layer

DTN Gateway

DTN vs. TCP/IP

Names and Addresses

Security

IPN (InterPlanetary Network) Example

IPN (InterPlanetary Network) ExampleStep 1: Bundle Creation at Source

IPN (InterPlanetary Network) ExampleStep 2: Transmission by Source

IPN (InterPlanetary Network) ExampleStep 3: First Hop Bundle Processing/Forwarding

IPN (InterPlanetary Network) ExampleStep 4: Second Hop Bundle Processing/Forwarding

IPN (InterPlanetary Network) ExampleStep 5: Bundle Reception at Destination

THE END

Questions?