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Delay Tolerant Networks

Delay Tolerant Networks. Roland Cheng. Inter-planetary Communication ~100 × 10 6 km. PAN ~1m. LAN ~100 m. MAN ~10 km. WAN ~1,000 km. Internet ~10,000 km. Outline. Review Internet protocol stack Internet vs. Delay Tolerant Networks Lagrange point relays Summary. 5 Layer TCP/IP Model.

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Delay Tolerant Networks

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  1. Delay Tolerant Networks Roland Cheng

  2. Inter-planetary Communication ~100×106 km PAN ~1m LAN ~100 m MAN ~10 km WAN ~1,000 km Internet ~10,000 km Mobile Communication

  3. Outline • Review Internet protocol stack • Internet vs. Delay Tolerant Networks • Lagrange point relays • Summary Mobile Communication

  4. 5 Layer TCP/IP Model Mobile Communication

  5. Outline • Review Internet protocol stack • Internet vs. Delay Tolerant Networks • Lagrange point relays • Summary Mobile Communication

  6. Assumptions in TCP/IP • Small propagation latencies • High data rates • Bidirectional, symmetric channels • Continuous connectivity A B Mobile Communication

  7. Assumptions in DTN • Large propagation delays • Low data rates • Asymmetric channels • Intermittent connectivity Mobile Communication

  8. Bundling Protocol • Place another layer between application and transport layer • Bundling protocol (CFDP) • Keeps all data and meta data needed to transmit a packet until receive ACK (store-and -forwarding) • Transmits data optimistically • Routing of packets should take advantage of scheduled outage • Uses new ARQ algorithms that can handle long delays Mobile Communication

  9. Data Flow Example in DTN Mobile Communication

  10. Outline • Review Internet protocol stack • Internet vs. Delay Tolerant Networks • Lagrange point relays • Summary Mobile Communication

  11. Lagrange Point Relays Sun Earth Mobile Communication

  12. Lagrange Point Relays • A Lagrange point is a solution to the restricted 3-body problem • a small object at a Lagrange point will remain stationary relative to two large, orbiting masses, assuming only gravitational effects • Placing a relay station at L4 and L5 will provide alternative signal paths when no line-of-sight Mobile Communication

  13. Outline • Review Internet protocol stack • Internet vs. Delay Tolerant Networks • Lagrange point relays • Summary Mobile Communication

  14. Summary • TCP/IP is not suitable for interplanetary communication • Large propagation delays, intermittent connectivity • Bundling protocol extends the network stack by providing asynchronous store-and-forwarding service • Lagrange point relays can alleviate LOS occlusions Mobile Communication

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