SPONTANEOUS SOCIAL-NETWORKING
ON SMARTPHONES USING
DELAY-TOLERANT NETWORKS
CP4101 B.COMP DISSERTATION (H101850 )
CHEN JUNCHENG
SUPERVISOR: PROF CHAN MUN CHOON
AGENDA
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Motivation
Application Description
Challenges Faced (and Solutions)
Evaluation
Testing
Demo
2
RISE IN SMARTPHONE SALES
• Sale of smartphones has overtaken personal
computers in the year 2010
Source: International Data Corporation 3
RISE OF SOCIAL PROXIMITY APPS
• Applications where users discover others nearby
and interact with them
Application
Description
Downloads
Rating
Badoo
Chatting, dating, making
friends with people nearby
10m+
4.5
Skout
Discovering and meeting
new people around
10m+
4.1
Circle
Finding people nearby
with mutual interests
5m+
4.4
Sonar
Connect with friends and
like-minded people
nearby
1m+
4.1
As of: 2nd November 2013
4
Millions of dollars
RISE OF SOCIAL PROXIMITY APPS
Projected Growth:
$1.9 billion
Market for social proximity apps
5
SOCIAL PROXIMITY APPS
IMPLEMENTATION
• Location (typically GPS) data uploaded to a central
server
• Server determines who/what is nearby
• Client downloads the list of neighbors
• Client displays the neighbors to the user
6
PROBLEMS
• Battery consumption: Use of 3G + GPS is heavy on
battery
• Server-Reliance: Fails to function in absence of
internet connectivity
• Bandwidth consumption: 3G consume user’s data
bandwidth
• Network congestion: Cell towers are overloaded
with small packets in network
7
THE FLITBY APPLICATION
• Build a Facebook-like application that is server-less
• Works without internet connectivity
• Use peer-to-peer communication in order to
exchange social data
• Saves battery by eliminating 3G and GPS usage
• Vision: people flit by one another and
spontaneously sharing social data using the
application, therefore it is called Flitby
8
P2P COMMUNICATION
• Phone-to-phone communications such as WifiDirect and Bluetooth
• Proximity is inherent – if I can contact you, you must
be nearby
• Shortcoming: only support one-hop transfers which
is very limited
• Solution: Use Mobile Delay-Tolerant Network (DTN)
9
MOBILE DELAY-TOLERANT NETWORK
• Network of all mobile users
• Topology changes rapidly because of high user mobility
• Users exchange data when they are within range of
one another
• These connections are intermittent and short-lived in nature
• No direct paths may exist between any two nodes
• Messages are stored and forwarded opportunistically for
multi-hop communication
A
B
C
10
EXAMPLE OF HOW FLITBY WORKS
Functionality #2:
Guys! Free ice cream
sandwich
Functionality
#1:here
Propagate social
at the Ice Cream
Store!
Post a status
data
11
EXAMPLE OF HOW FLITBY WORKS
Functionality #4:
Functionality #5:
#3:
View status post
Oh my with
god! Really?
Log
encounters
Make
comments
associated
with
other
users
and
like
them!
encounter
12
CHALLENGE #1
• State Inconsistencies
• In a decentralized network, it takes time for social data to
propagate through the network
• Therefore, it is usually the case that clients have a subset of
the global state and this can be inconsistent.
• Merging of subsets during chance encounters can warp the
meaning of messages
13
CHALLENGE #1
Juncheng
Dora
Bill
Tom
Does anyone know if
there’s a lecture next
Monday?
Most recent first
J
D
B
T
14
CHALLENGE #1
Juncheng
Dora
Bill
Tom
Does anyone know if
there’s a lecture next
Monday?
J
D
B
T
15
CHALLENGE #1
Juncheng
Dora
Bill
Tom
Does anyone know if
there’s a lecture next
Monday?
Yes, there’s school on
Monday. Deepavali is
on Saturday.
J
D
B
T
16
CHALLENGE #1
Juncheng
Dora
Bill
Tom
Does anyone know if
there’s a lecture next
Monday?
Yes, there’s school on
Monday. Deepavali is
on Saturday.
Nope, it’s supposed to
be a public holiday in
lieu of Deepavali being
on Sunday
J
D
B
T
17
CHALLENGE #1
Juncheng
Dora
Bill
Tom
Does anyone know if
there’s a lecture next
Monday?
Yes, there’s school on
Monday. Deepavali is
on Saturday.
Nope, it’s supposed to
be a public holiday in
lieu of Deepavali being
on Sunday
I agree!
J
D
B
T
18
CHALLENGE #1
Juncheng
Dora
Bill
Tom
Does anyone know if
there’s a lecture next
Monday?
Yes, there’s school on
Monday. Deepavali is
on Saturday.
Nope, it’s supposed to
be a public holiday in
lieu of Deepavali being
on Sunday
I agree!
J
D
B
T
19
CHALLENGE #1
Juncheng
Dora
Bill
Tom
Does anyone know if
there’s a lecture next
Monday?
Yes, there’s school on
Monday. Deepavali is
on Saturday.
Nope, it’s supposed to
be a public holiday in
lieu of Deepavali being
on Sunday
I agree!
Uhm… So which is it?
J
D
B
T
20
CHALLENGE #1
Juncheng
Dora
Bill
Tom
Does anyone know if
there’s a lecture next
Monday?
Yes, there’s school on
Monday. Deepavali is
on Saturday.
Nope, it’s supposed to
be a public holiday in
lieu of Deepavali being
on Sunday
I agree!
Uhm… So which is it?
The problem is that we did not capture the context of the comments!
21
CHALLENGE #1
• Solution
• Present information in a coherent manner to the user
• Tapping on a particular comment should show the context in
which that comment was made
22
CHALLENGE #1
Juncheng
Dora
Bill
Tom
Does anyone know if
there’s a lecture next
Monday?
Yes, there’s school on
Monday. Deepavali is
on Saturday.
Nope, it’s supposed to
be a public holiday in
lieu of Deepavali being
on Sunday
I agree!
Uhm… So which is it?
23
CHALLENGE #1
Juncheng
Dora
Bill
Tom
Does anyone know if
there’s a lecture next
Monday?
Yes, there’s school on
Monday. Deepavali is
on Saturday.
Nope, it’s supposed to
be a public holiday in
lieu of Deepavali being
on Sunday
I agree!
Uhm… So which is it?
24
CHALLENGE #1
Juncheng
Dora
Bill
Tom
Does anyone know if
there’s a lecture next
Monday?
Yes, there’s school on
Monday. Deepavali is
on Saturday.
Nope, it’s supposed to
be a public holiday in
lieu of Deepavali being
on Sunday
I agree!
Uhm… So which is it?
25
CHALLENGE #1
Juncheng
Dora
Bill
Tom
Does anyone know if
there’s a lecture next
Monday?
Yes, there’s school on
Monday. Deepavali is
on Saturday.
Nope, it’s supposed to
be a public holiday in
lieu of Deepavali being
on Sunday
I agree!
Uhm… So which is it?
26
CHALLENGE #2
• Communication Challenges
• Exchange of information relies upon often brief contacts
with other users
• Not enough time to exchange all data
• Social network data is monotonically increasing
• Infeasible to exchange all data with users
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CHALLENGE #2
• Solution
• Given that connection time is short-lived
• Exchange of information should be prioritized based on one’s
interest (friends or otherwise)
• Reduce redundancy and only send new information in form of
deltas
• Any connection/encounters with any other clients is purely
opportunistic
• Spread other non-priority data once priority data is exchanged
• Mobility patterns of users may also be used to prioritize
exchanges but this topic itself is its own research topic
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CHALLENGE #2
Client A
Client B
send friends list,
status IDs with last modified time,
comment IDs with last modified time
loop
[while there are updates for A's friends' statuses/comments]
send status delta
Priority Data
acknowledgement
loop
[while there are status/comment updates to be sent]
send status delta
Non-priority Data
acknowledgement
close connection
29
CHALLENGE #3
• Facebook Synchronization
• Good idea to synchronize social networking data back to
Facebook periodically
• However, Facebook doesn’t allow arbitrary timestamps on
status/comment posts.
• It is difficult to coordinate the clients to preserve the order of
comments
30
CHALLENGE #3
. ..
Aggregates and syncs
Flitby Proxy
Facebook Servers
Solution: Use a proxy server to store
social networking data from clients and
commit to Facebook periodically.
(Unimplemented)
31
CHALLENGE #4
• Privacy
• Flitby uses opportunistic routing through intermediate nodes
• Intermediate nodes can access other people’s data
• Negotiating cryptographic keys is difficult due to large
delay.
• Solution
• Use a server to negotiate/distribute cryptographic keys.
(Unimplemented)
32
FLITBY ARCHITECTURE
Flitby Android Application
User Activities
(GUI)
Facebook Android
SDK API
Syncher
User
Data
User
Discovery
DTN
Middleware
API
Facebook Servers
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DATABASE
•
•
•
•
•
User Table
Group Table
Status Table
Comment Table
Encounter Table
34
EVALUATION
• Devices used:
• Samsung Galaxy SII (v4.3.1)
• Samsung Galaxy SIII (v4.1.2)
• Nexus 4 (v4.3)
• Wi-Fi used:
• IEEE 802.11g
• Development Environment:
• Android Developer Tools v22.0.5-757759
35
EVALUATION
• Time taken for DTN messages of varying sizes to be
sent from node to node. (Using TCP over Wi-Fi)
5000
y = 0.9841x + 420.21
R² = 0.9993
time taken (ms)
4500
4000
3500
3000
2500
2000
1500
1000
500
0
0
500
1000
1500
2000
2500
Data size (kB)
3000
3500
4000
4500
36
EVALUATION
• Throughput of DTN based on previous data
• For comparison: In the US, 3G has a data bandwidth of
3.84Mbps/1.44Mbps (practical download/upload rate)
Data Size (kB)
Throughput (Kbps)
256
3046.973048
512
4432.532912
1024
5736.91607
2048
6726.659592
4096
7361.685488
37
EVALUATION
• Using Samsung Galaxy S2 and 3G network
• 10 trials were conducted
• Time recorded was time taken for the first screen to
completely load
First startup
Subsequent
startup
Flitby
5.97s
1.11s
Facebook
9.89s
6.63s
38
TESTING
• Android Strict Mode
Client A
• option in the application
that would detect & log
undesirable practices
Client B
Client C
Client D
Make a
status post
synchronize post
synchronize post
synchronize post
Key:
Application open
Make
comment c1
• Manual Testing
synchronize c1
• 1 phone test case
• 2 phones test case
• Systems Testing
synchronize c1
Make
comment c2
Make
comment c3
synchronize c3
synchronize c3
loop
[not synchronized]
synchronize
synchronize
synchronize
synchronize
synchronize
Make
comment c4
loop
[not synchronized]
synchronize
39
WHAT FLITBY LOOKS LIKE
This is your profile information
These are the people you
have encountered with
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WHAT FLITBY LOOKS LIKE
This is your profile information
Type in a new status here
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WHAT FLITBY LOOKS LIKE
Status Post Owner
Status Post
Write a response here
Comments
42
DEMO
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CONCLUSION
• We were able to develop Flitby as a decentralized
social application that functions with DTN
• We tackled 2 of the problems presented in this
presentation
• Communication Challenges (Application Routing Protocol)
• State Inconsistencies (View Hierarchy)
• Future work could involve:
• Expanding the social network feature sets
• Improving Privacy
• Synchronization of social data back to Facebook
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END
• Thank you for your attention!
• Questions?
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