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

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

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

“Store, carry and forward” modelUtilize redundancy to increase the success

probabilityBut,

flooding overhead

Epidemic routing

4

Based on Epidemic Routing SchemeUse “delivery predictability” to reduce

flooding overhead

Delivery predictabilityPinit: an initialization constant

Nodes that are often encountered have a high delivery predictability.

PROPHET routing

5

]1,0[ )1( ,),(),(),( initinitoldbaoldbaba PPPPP

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)

1, , /S D S DP T T

Fixed time interval

UPDOWN

UPDOWN

Time line

Contact between A and C

Contact between B and C

T

Super stars avoidance (load balance)Contact Duration Ratio( Prophet CD)

PROPHET Enhancements (PROPHET_CD)

7

1, , ,

1

/N

S D S D S ii

P T T

Total contact

duration of Node S

T

A

B

C D C

C

Time line

Use coding skill to increase success probability

Apply Network Coding on the packet

Network Coding

8

DTNSIM : A Java-based simulatorA Real-world wireless trace

ZebraNet1ZebraNet2 (decreasing 30% contact

durations)

Simulation

9

ZebraNet1 ZebraNet2Avg contact duration/pair/day(sec) 22,211 12,825

Avg # of contacts/pair/day 2.06 2.06Number of nodes 34 34

Trace Name ZebraNet1, ZebraNet2CBR Traffic (1 MB/msg) 1 msg/hour

Contact bandwidth 1 MB/sH (hop count limit) 5

m(computation depth) 4T (time interval) 2 dayNumber of pairs 1, 10, 20, 30

Buffer size 400 MBSimulation time 16 day

Pinit / γ / ω 0.75 / 0.98 / 0.25

Simulation Settings

10

ZabraNet1

PROPHET vs. Enhanced PROPHET

11

CA,C CA,D

CB,

C

Time line

Node ANode B

PROPHET vs. Enhanced PROPHET

12

0

0.2

0.4

0.6

0.8

1

0 200000 400000 600000 800000 1e+006

Del

iver

y R

atio

CC

DF

Latency (seconds)

PROPHETPROPHET_CUPROPHET_CD

30 node pairs

ZebraNet2

PROPHET vs. Enhanced PROPHET

13

Routing comparison

14

Routing comparison: various error rate

16

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

Thank you

18