Trends and Challenges in Delay Tolerant Network (DTN) or Mobile Opportunistic Network (OppNet)

1.
Trends
and
Challenges
in
Delay
Tolerant
Network
(DTN)
or
Mobile
Opportunis<c
Network
(OppNet)
Special
Talk
on:
Dr.
Mazlan
Abbas,
UTHM
2
April
2014

2. A little bit about the Speaker

3. Outline
• Motivation
• History of DTN
• Trends and Challenges in DTN
• Routing in DTN
• Performance of DTN in Emergency Scenario
• DTN Applications
• Future Work

4. Issues of Communications During Disasters and
Emergency
Terrorist Attack Hurricane
Tsunami Earthquake
Lack of
adequate
communi
cations

5. Opportunistic Networks (OppNets)
To enable communication between source and destination
without the support of a fixed network infrastructure

6. 6
3G
3G
3G
3G Base
station
Normal

7. 7
3G
3G
3G
3G Base
station
During Disaster
X X
XX

8. History of the DTN Motivation

9. Imagine This…
If I say a “Hello” to you and you hear it
after …
9 hours!!!

10. Some Fast facts
Time
taken
by
light
–
Earth
–
Jupiter
:
32.7
min
–
Earth
–
Saturn
:
76.7
min
–
Earth
–
Pluto
:
5.5
hours
–
Earth
–
Voyager1
:
13
hours
–
Earth
–
Voyager2
:
10.4
hours.

11. [Source: TERENA Networking Conference 2000, 24 May 2000, Scott Burleigh, Vint Cerf, Bob Durst, Adrian Hooke, Keith
Scott, Eric Travis, Howard Weiss

12. History of Delay Tolerant Network
• Interplanetary Internet (IPN) is a NASA research project led by
Vint Cerf in 1998.
• The basic idea is to try to make data communications in space/
between planets.
• IPN became the most fundamental basis for DTN architecture
and protocol suite.
• The Interplanetary Internet is a disconnected, store-and
forward ‘network of Internets’ based on a wireless
backbone with huge delays (The delay in sending or
receiving data from Mars takes between 3.5 to 20
minutes at the speed of light) and error prone links
• Failing of IP/TCP in space missions
– End-to-end path exist
– Small delays

13. Delay Tolerant Networking (DTN)
• DTN is a set of protocols that
act together to enable a
standardized method of
performing store-carry-and-
forward communications.
• Characteristics of DTN:
i. Intermittent connectivity
– No end-to-end path between
source and destination
ii. Long variable delay
– Long propagation delays
between nodes
A
B
B
C
C D
Source
Store
Carry
Forward
Store
Carry
Forward
Delay Tolerant Network (DTN) = Mobile Opportunistic Network (OppNet)

14. Opportunistic Mobile Networks (DTN)
Store-Carry-Forward
• Opportunistic networks typically wireless
• Nodes are typically handheld devices carried by people
• No infrastructure required
• Nodes communicate directly with each other

15. Why Ad Hoc Networks ?
• Setting up of fixed access points and backbone
infrastructure is not always viable
– Infrastructure may not be present in a disaster area or
war zone
– Infrastructure may not be practical for short-range
radios; Bluetooth (range ~ 10m)
• Ad hoc networks:
– Do not need backbone infrastructure support
– Are easy to deploy
– Useful when infrastructure is absent, destroyed or
impractical

16. Many Applications
• Personal area networking
– cell phone, laptop, ear phone, wrist watch
• Military environments
– soldiers, tanks, planes
• Civilian environments
– taxi cab network
– meeting rooms
– sports stadiums
– boats, small aircraft
• Emergency operations
– search-and-rescue
– policing and fire fighting

17. Leveraging The Power of Mobile
Phones
• 3.3 billion people worldwide use cell phones
• Mobile phones are integrated with Wi-Fi, cameras, Bluetooth,
and others. – creates a huge number of contact opportunities

18. Smartphones – The Enabler
CameraGPS
WiFi
Big
Storage
CPU
Power

19. 19
3G
WiFi
WiFi
WiFi
3G
3G
3G Base
station
OppNet in Emergency Response Scenario
Public Safety

20. 20
3G
WiFi
WiFi
WiFi
3G
3G
Base
Station down
X X
XXWiFi WiFi
OppNet in Emergency Response Scenario
Public Safety
Smartphones (Nodes) can
be carried by “Pedestrians”
or “Vehicles”
Send “SOS” messages
Send photos of victims or
self
Can we send videos?
What kind of file size?

21. 21
3G
WiFi
WiFi
WiFi
3G
3G
Base
Station down
X X
XXWiFi WiFi
Internet
Internet
Ability to Connect to Internet at
Remote Ends
Public Safety
Question: Can smartphones help
us during Emergency Situation?

22. 22
3G
WiFi
WiFi
WiFi
3G
3G
Base
Station down
X X
XXWiFi WiFi
Internet
Internet
DTN Gateway
DTN Gateway

23. Challenges in Mobile Environments
· Limitations of the Wireless Network
· packet loss due to transmission errors
· variable capacity links
· frequent disconnections/partitions
· limited communication bandwidth
· Broadcast nature of the communications
· Limitations Imposed by Mobility
· dynamically changing topologies/routes
· lack of mobility awareness by system/applications
· Limitations of the Mobile Computer
· short battery lifetime
· limited capacities

24. Other Applications of DTNs
Wildlife monitoring
1
3
2
Communication in
rural villages
Emergency/military

25. Application Scenario – Wildlife
Monitoring
• ZebraNet
Do zebras in the African bush have a pattern of
migration or do
they just move around in a random fashion
across the year?
• A Princeton University project
• Custom tracking collar with GPS (node) is put on the
neck of the zebra.
• Nodes record zebra’s location and stores in memory.
• Nodes carry the data until meet another node.
• Exchanges data with another zebra when in
communication range.
• Mobile base station (MBS) collects data from collars
when researchers are in the field.
• MBS is not fixed, rather it moves and is only
intermittently available
• Physical presence of the researchers is no longer
required at the deployment site in order to collect and
publish zebra mobility pattern data.
• Network connectivity is intermittent and opportunistic

26. Application Scenario –
Communication in Rural Villages
• DakNet
Goal: Bring Internet connectivity to rural areas
• It is aimed at providing cost-effective
connectivity to rural villages in India,
where deploying a standard Internet
access is not cheap.
• Kiosks are built up in villages and are
equipped with digital storage and
short-range wireless communications.
• Mobile Access Points (MAPs)
mounted on buses, motorcycles, etc.,
exchange data with the kiosks
wirelessly.
• MAPs may also download requested
info (news, music, etc.) and bring it to
villages.
• Kiosks connectivity
• Dial-up - slow (28 kbps)
• Short range communication

27. Application Scenario – Military
When M1 and M2 are both
connected, data is
transferred directly.
When the link between M2 and
satellite is disconnected, data is
transferred to HQ for storage and
later delivery to M2.
Ziyi Lu and Jianhua Fan. Delay/Disruption Tolerant Network and its Application in Military Communications, International Conference On Computer Design And Applications (ICCDA
2010), 2010.
When M2 is reconnected, data
stored at HQ is delivered, even if
M1 is disconnected.
Soldiers need to be able to communicate with each other in the battlefield
DTN technology can be used to achieve the communication
even though the end-to-end connection does not exist.

28. Challenges
Challenging Research in DTN/OppNet
ROUTING TRUST

29. C1
C6
C3
C2
C3
C5
Node Mobility
Source
Destination
Example: Disaster relief efforts, mining operations, health campaigns
In emergency situations, entities with any sensing capabilities such as cellphones with
GPS or desktops equipped with surveillance cameras, can be especially valuable for the
OppNet.
C4
Routing Challenges

30. N1
N2
Mobility Pattern
Node Speed
Type of Communication
Transmission Range
Buffer Size Battery LifeTime-to-LiveMessage Size
Routing Mechanism
Number of Nodes
Size of Area
Factors That Impact Performance

31. Mobility Model

32. Random Movement
Random Walk Random Waypoint
Mobility model
Random
movement
Human behavior
based movement
Map-constrained
random
movement
• Each mobile nodes starts at a random
location and staying there for a certain
period of time (pause time) and at the
end of the pause time, the nodes select
a random destination and move to the
selected destination at a random speed.
• Each mobile nodes starts at a random
location and then move to a new location
by randomly choosing a direction and
speed.

33. Map-constrained random
movement
e.g. KLCC (A) to KL Pavilion (B)
• move from stop to stop using
shortest paths
• nodes follow certain route
(e.g. bus)
Mobility model
Random
movement
Human behavior
based movement
Map-constrained
random
movement
Random Map-Based Movement Shortest Path Map-Based Movement Routed Map-Based Movement

34. Can we do better?

35. Closing the Gap
Opportunistic
Networks
Social
Networks+
• Close the gap between
human and network
behavior
• Opportunistically follow the
way humans come into
contact
• Exploit human relationships
• Built more efficient and
trustworthy protocols

36. Human, electronic, and virtual social networks. Embedding the social relationships in the
electronic world identifies at least two levels in an opportunistic environment: an electronic
social network (where relationships depend on the physical properties) and a virtual social
network that builds an overlay atop the electronic social network.

37. Social Network Routing
Social
Contact
The social importance of a
user in facilitating the
communication among other
users
Social
Interest
Users with common interest are
usually friends and tend to
contact each other more
frequently
Social
Relation
Users are formed into groups
according to their social
relationship
A technique for determining the paths that data takes across
networks based on social behavior patterns (social contact,
interest, and relationships)

38. Human Behavior Based
Movement
Mobility model
Random
movement
Human behavior
based movement
Map-constrained
random
movement
EKMAN, F., KER¨A NEN, A., KARVO, J., AND OTT, J. Working Day Movement Model. In Proc. 1st ACM/SIGMOBILE Workshop on Mobility
Models for Networking Research (May 2008).
• Bring more reality of human movement
patterns during a working day
• It produces similar Inter-contact times and
contact durations as real world traces
• All nodes move on a real world map
• There are three major activities:
1. Staying at home – node wake up in the
morning
2. Working at the office - go to the office
and works 8 hours
3. Doing some activity with friends in the
evening
• Use different transportation between activities
(bus, car or walking)
Working Day Movement Model (WDM)

39. Routing

40. Routing
When and where to forward data?
School bus is just
coming
Jack is at
school
John have a
message for
Jack

41. This is
for Mrs.
Wilson
I will give
the copy to
everyone I
meet, and
hopefully it
will reach her
Concept: Floods messages into the
network
Goal: Maximize message delivery
rate
Disadvantages:
• High resources usage (buffer)
• High overhead
Epidemic: Epidemic Routing for Partially
Connected Ad Hoc Networks
[Ref: A. Vahdat and D. Becker. Epidemic Routing for Partially Connected Ad Hoc Networks. Technical Report CS-2000-06, CS. Dept.
Duke Univ., 2000.]
Epidemic
Spray and Wait
Routing protocol
Spray and Focus
Prophet
Mrs. Wilson

42. Concept: Use past encounters to
predict future best
Goal: Improve the performance of
Epidemic
Disadvantage: No guarantee to meet
a better node in a message life time
Prophet: Probabilistic Routing Protocol using
History of Past Encounters and Transitivity
This is
for Mrs.
Wilson
Let me do it. I
will
probability
meet her as
usual
[Ref: A. Lindgren, A. Doria, and O. Schelen. Probabilistic Routing in Intermittently Connected Networks. ACM Mobile Computing
and Communications Review, 2003.]
0.3
S D
A
B
0.5
X
1.0
0.5
?
A or B ?
0.7
Decision based on delivery probability
and transitivity (the probability for a
node to encounter a destination)
Epidemic
Prophet
Routing protocol
Spray and Focus
Mrs. Wilson
Spray and Wait

43. Received messages with different Queue size
Prophet has higher received messages than
Epidemic
Number forwarded messages with different Queue size
Prophet has lower overhead than Epidemic
100m
50m
100m
50m
Epidemic
Epidemic
Prophet
Simulation parameters
Simulation area: 1500 x 300 m
Number of nodes: 50
Mobility model: Random Waypoint
Epidemic Prophet
Prophet
Epidemic
Prophet

44. Concept: Controlled flooding / Limit number of
copies made
Goal: to reduce the overhead of Epidemic
Disadvantage:
• High delay
• Random Movement (If the nodes that receive a
copy of the bundle never cross paths with the
destination, the system fails completely)
Spray and Wait:
Efficient Routing in Intermittently Connected
Mobile Networks: The Multiple-copy Case
This is
for
Mrs.
Wilson
I will spread
four copies
to first four
that I meet,
and
hopefully it
will reach
her
Spray Phase
Source will generate and
distribute a small number
of copies to only a few
relay
Wait Phase
Each relay carries its copy until it
meets the destination and delivers
it directly to the destination (each
relay will forward its copy only to
the destination)
Epidemic
Spray and Wait
Routing protocol
Spray and Focus
Prophet
[Ref: Spyropoulos, T., Psounis, K., and Raghavendra, C. S. Spray and Wait: An Efficient Routing Scheme for Intermittently Connected
Mobile Networks. In Proc. of the ACM SIGCOMM Workshop on Delay-Tolerant Networking (WDTN) , 2005.]
Mrs. Wilson

45. Simulation parameters
Simulation area: 200 x 200 m
Number of nodes: 100, 200
Mobility model: Random Waypoint
Epidemic
Spray & Wait Spray & Wait
Epidemic
The number of transmissions for Spray and Wait are very less
than Epidemic

46. This is
for Mrs.
Wilson
I will spread
four copies to
first four that I
meet, and the
four person will
forward that
copies to
someone else
closer to Mrs.
Wilson, and
hopefully it will
reach her
Spray and Focus:
Efficient Mobility-assisted Routing for Heterogeneous
and Correlated Mobility
Concept: Limit number of copies made /
controlled flooding
Goal: To reduce the delay of Spray and
Wait
[Ref: T. Spyropoulos ,and K. Psounis. Spray and Focus: Efficient Mobility-assisted Routing for Heterogeneous and Correlated Mobility.
Proc. of IEEE Percom International Workshop on Intermittently Connected Mobile Ad Hoc Networks, March 2007.]
Source will generate and
distribute a small number
of copies to only a few
relay
Each relay will forward its copy
to another relay (the selection
of relay is based on single-
copy utility based scheme)
Spray Phase Focus Phase
Epidemic
Spray and Wait
Routing protocol
Spray and Focus
Prophet
Mrs. Wilson

47. [Ref: Jianwei Niu, Jinkai Guo, Qingsong Cai, Norman Sadeh, and Shaohui Guo. Predict and Spread: an Efficcient Routing Algorithm
for Opportunistic Networking. Proc. of IEEE Wireless Communications and Networking Conference (WCNC), March 2011.]
When the value of TTL increases, the delivery latency
decreases
Spray and Focus has lower delivery latency than Spray
and Wait
Spray&Wai
t
Spray&Foc
us
When the value of TTL increases , the delivery ratio
increase
Spray and Focus seem to perform slightly better
than Spray and Wait in term of delivery ratio
Spray&Wai
t
Spray&Foc
us
Simulation parameters
Simulation area: 4500 x 3400 m
Number of nodes: 300
Transmit range: 10 m
Transmit speed: 250 Kbyte/s
Mobility model: Map Route
Movement

48. MaxProp:
Routing for Vehicle-Based Disruption-Tolerant Networks
[Ref: J. Burgess, B. Gallagher, D. Jensen, and B. Levine. MaxProp: Routing for Vehicle-Based Disruption-Tolerant Networks. Proc. of the
25th INFOCOM, 2006.]
This is
for Mrs.
Wilson
My packets
are full, and I
had the
message long
enough, and I
am sure
someone else
gave the
message to
her
Concept: Packet Dropping Policy
(schedule packets transmission to its peers and
determines which packets should be deleted
when buffer space is almost full. Packets are
schedule based on encounter history of nodes
throughout the network)
Goal: To increase the delivery rate and lower
latency
Disadvantage: High processing cost in large scale
networks
Epidemic
Prophet
Spray and Wait
Routing protocol
Spray and Focus
MaxProp

49. S
D
C1
C2
C1
C3
Node Mobility
Source
Destination
Can Opportunistic Network support
Emergency Scenario?
Example: Disaster relief efforts, mining
operations, health campaigns
In emergency situations, entities with any sensing
capabilities such as cellphones with GPS or desktops
equipped with surveillance cameras, can be especially
valuable for the OppNet.

50. Performance Evaluation of Binary Spray and Wait OppNet
Protocol in the Context of Emergency Scenario
Mazlan Abbas, Nur Husna and Norsheila Fisal
PerNEM 2013
In Cooperation with the 3rd International Workshop on IEEE PerCom 2013
Pervasive Networks for Emergency Management
March 22, 2013, San Diego, California, USA
[Note: Check Results in Slideshare - http://www.slideshare.net/mazlan1/per-nem-2013-slideshare ]

51. Future Applications of DTN
(OppNet)

52. OpportunisMc
Network
Weather
Monitoring
Water
Infrastructure
Control
Public
Surveillance
Camera
Abandon their normal daily functions…… and become “helpers”
Help to sense fires
and flooding
Help to sense vehicular
movement and traffic
jams
Help to search
for images of
human victims
During Disaster….
Benevolent OppNet scenario – “Citizens called to arms”

53. OpportunisMc
Network
Weather
Monitoring
Water
Infrastructure
Control
Public
Surveillance
Camera
Recruit “helpers” to analyze wind patters that can contribute to a
faster spread of poisonous chemicals.
Help to sense wind
patterns
Help to sense vehicular
movement and traffic
jams
Help to locate
police and
military
personnel
Before City Siege ….
Malevolent OppNet scenario – “Bad guys gang up”

54. Give it to me, I have
1G bytes phone
flash.
I have 100M bytes of
data, who can carry
for me?
I can also
carry for you!
Thank you but you are
in the opposite
direction!
Don’t give to me! I am
running out of storage.
Reach an
access
point.
Internet
Finally, it
arrive…
Search Roar.mp3
for me
Search Roar.mp3
for me
Search
Roar.mp3 for
meThere is
one in my
pocket…
Consumer Applications

55. Hi what’s up?
There is a mega sale!!
Cool.. I m gonna tell my friend!!
Thanks buddy
Shopping Malls

56. Terminal
Bus
A
Terminal
Bus
B
Terminal
Bus
C
Terminal
Bus
D
Synchronize
with
“local
contents”
Smart Transportation

57. 57
Summary
• Opportunistic Networks (OppNets) are very useful in
the context of emergency scenarios
• We discovered that Binary Spray and Wait Protocol
is one good option for routing
• Smartphones seems to be a good potential
candidate communications tool in emergency
scenarios
• Speedier nodes (vehicles) require smaller Message
size (images rather than videos).

58. Future Work
• Requires actual datasets (emergency scenarios) for
mobility model
• Mixed mobility scenarios (pedestrians plus vehicles)
• Find better battery efficient methods
• Further refinements to Spray & Wait Protocol with
other parameters such as Contact Time etc.
• Implementation on smartphones – e.g. WiFi Direct
802.11ac or Bluetooth

59. EMAIL: mazlan@gmail.com LINKEDIN: my.linkedin.com/in/mazlan/
TWITTER: mazlan_abbas SLIDESHARE: www.slideshare.net/mazlan1
FACEBOOK: www.facebook.com/drmazlanabbas