Delay Tolerant Networking

1. Introduction to Delay Tolerant Networks Delay Tolerant Networking Dave Wick RVS Group University of Berne

2. Introduction to Delay Tolerant Networks Overview • Motivating a Delay Tolerant Network • DTN Framework • Routing Ideas • Real World Applikation: Zebranet • Summary & Outlook

3. Introduction to Delay Tolerant Networks Overview • Motivating a Delay Tolerant Network • DTN Framework • Routing Ideas • Real World Applikation: Zebranet • Summary & Outlook

4. Mars Mars Mars Jupiter u b Earth Introduction to Delay Tolerant Networks Outer Space Network

5. Introduction to Delay Tolerant Networks What is a DTN? • Network with intermittent connectivity • Long & variable delays • Asymmetric data rates • High error rates • Consists of heterogenious networks

6. Introduction to Delay Tolerant Networks Why do we need DTN research? • To cover regions with no infrastructure • Networks with pedestrians • Intelligent highways • Military battlefield • Challange for academic research • First the technology, then the need

7. Introduction to Delay Tolerant Networks Challenges of a DTN • Naming & addressing • Routing • Data transmission (retransmission, flow control) • Application interface • Security • QoS (prioritisation) • Timesynchronization

8. Introduction to Delay Tolerant Networks Overview • Motivating a Delay Tolerant Network • DTN Framework • Routing Ideas • Real World Applikation: Zebranet • Summary & Outlook

9. Introduction to Delay Tolerant Networks The DTN framework • Overlay architecture • Network of regional networks • Gateways, routers and hosts • Delay tolerant between & within regions • Unique identifiers {region id, host id} Gateway Region B Region A Address {region b, host x}

10. Apps Apps Bundle layer Region specific layers Region specific layers Region specific layers Introduction to Delay Tolerant Networks The DTN framework • Bundle concept • Bundlelayer between app- & region specific layers • Use of ‚bundles‘ instead of packets • Bundle store & forward-routing • Custody transfer • Security • Prioritization • No routing algorithm proposed

11. Introduction to Delay Tolerant Networks Overview • Motivating a Delay Tolerant Network • DTN Framework • Routing Ideas • Real World Applikation: Zebranet • Summary & Outlook

12. Introduction to Delay Tolerant Networks Routing algorithms • Epidemic routing • CAR, Context Aware Routing • DTC, Disconnected Transitive Communication • MoVe, Motion Vector Routing

13. Introduction to Delay Tolerant Networks Assumptions

14. Introduction to Delay Tolerant Networks Context Aware Routing • Calculates delivery probability for every known host • Broadcast information in cloud • Using the underlying proactive routing protocol • Every node maintains a table containing the probabilities • Send message directly if destination is in cloud • Else send message to host with highest probability • If host is unknown, deliver to host with highest mobility

15. Introduction to Delay Tolerant Networks Delivery probability • Adaptive weighted utility function • Change rate of connectivity • Probability of colocation with destination-host • Weights are adapted at runtime

16. Introduction to Delay Tolerant Networks CAR roundup • Assets & drawbacks • Low number of messages on propagation • Lightweight algorithm • Table setup required • Learning phase required • Doesn‘t scale well

17. Introduction to Delay Tolerant Networks Disconnected Transitive Communication • Based as well on calculation of a utility • Extension with additional measures • 3 phases to collect information and send data • Utility calculation • Most recently noticed • Most frequently noticed • Future plans • Power • Rediscovery interval • Source defined utility function

18. Introduction to Delay Tolerant Networks DTC roundup • Assets & drawbacks • More independent measures • Adaptive, individual utility function • Capsuled utility calculation • Heavy traffic on demand • No implementation

19. Destination Source Node B Introduction to Delay Tolerant Networks Motion Vector • Routing based on actual movement of the node • Needs location information of itself and destination • Motionvector based on past locations • Broadcast hello-message to neighbors • Send to host with closest distance (cd) cd ß

20. Introduction to Delay Tolerant Networks MoVe roundup • Assets & drawbacks • No history, no learning needed • Easy to implement algorithm • Position data needed • Performs very badly in real world

21. Introduction to Delay Tolerant Networks Overview • Motivating a Delay Tolerant Network • DTN Framework • Routing Ideas • Real World Applikation: Zebranet • Summary & Outlook

22. Introduction to Delay Tolerant Networks Zebranet • The goal is tracking of zebras in wildlife • Position, direction, heart rate, body temperature etc. • Constraints • One year of operation • Low weight (<1 kg) • Wide range (>1000 km2) • No fixed basestation • High data delivery rate

23. Base station (mobile) Introduction to Delay Tolerant Networks Zebranet implementation • Collar design • Low & high range radio • Solar panels, battery • 4 mbit flash memory • Routing • Flooding • History based Zebras

24. Introduction to Delay Tolerant Networks Overview • Motivating a Delay Tolerant Network • DTN Framework • Routing Ideas • Real World Applikation: Zebranet • Summary & Outlook

25. Introduction to Delay Tolerant Networks Summary & Outlook • Framework allows to implement new algorithms quite fast • Routing performance depends strongly on chosen scenario • Realworld applications are rare and have experimental character • Focus on improvement of existing protocols • Decrease chattyness • Improve buffer allocation & deletion • Message duplication for more efficient delivery • Refine routing algorithms • Merging different routing approaches