1. Chien-Shiu Lin, Wei-Shyh Chang, Ling-Jyh Chen, Cheng-Fu Chou, and Ting-Kai Huang

2. Delay /Disruption Tolerant Networks (DTNS) attracted increasing attention recently. What’s the crucial factors for a successful routing algorithms in Delay/Disruption Tolerant Networks? Motivation 2

3. Analysis of several kinds of routing schemes Epidemic routing PROPHET routing NC routing Propose two enhancements for PROPHET Contact utilization (PROPHET_CU) Contact duration ratio (PROPHET_CD) Our contributions 3

4. “Store, carry and forward” model Utilize redundancy to increase the success probability But, flooding overhead Epidemic routing 4

5. Based on Epidemic Routing Scheme Use “delivery predictability” to reduce flooding overhead Delivery predictability P init : an initialization constant Nodes that are often encountered have a high delivery predictability. PROPHET routing 5

6. The number of contacts vs. the duration of contact Contact Utilization (Prophet_CU) PROPHET Enhancements (PROPHET_CU) 6 Total contact duration of pair (S,D) Fixed time interval UP DOWN UP DOWN Time line Contact between A and C Contact between B and CT

7. Super stars avoidance (load balance) Contact Duration Ratio( Prophet CD) PROPHET Enhancements (PROPHET_CD) 7 Total contact duration of Node S T A B CDC C Time line

8. Use coding skill to increase success probability Apply Network Coding on the packet Network Coding 8

9. DTNSIM : A Java-based simulator A Real-world wireless trace ZebraNet1 ZebraNet2 (decreasing 30% contact durations) Simulation 9 ZebraNet1ZebraNet2 Avg contact duration/pair/day(sec)22,21112,825 Avg # of contacts/pair/day2.06 Number of nodes34

10. Trace NameZebraNet1, ZebraNet2 CBR Traffic (1 MB/msg)1 msg/hour Contact bandwidth1 MB/s H (hop count limit)5 m(computation depth)4 T (time interval)2 day Number of pairs1, 10, 20, 30 Buffer size400 MB Simulation time16 day P init / γ / ω0.75 / 0.98 / 0.25 Simulation Settings 10

11. ZabraNet1 PROPHET vs. Enhanced PROPHET 11 C A,C C A,D C B,C Time line Node A Node B

12. PROPHET vs. Enhanced PROPHET 12 30 node pairs

13. ZebraNet2 PROPHET vs. Enhanced PROPHET 13

14. Routing comparison 14

15. Routing comparison 15 10 node pairs 30 node pairs

16. Routing comparison: various error rate 16

17. We propose enhancement schemes on PROPHET. Contact duration is an important factor We study several DTN routing schemes and suggest suitable network environment for each routing protocol. Epidemic routing is sensitive to network loading. NC has best delivery ration in congestion situation. NC routing is vulnerable in network with high error rate Conclusion 17

18. Thank you 18