EVCCM: An Efficient VOIP
Congestion Control Mechanism
Presenter: Ming Cao, Hadi Otrok, Benwen Zhu, Noman Mohammed, Prabir Bhattacharya
Computer Security Laboratory
Concordia Institute for Information Systems Engineering(CIISE)
Concordia university Montreal, QC, Canada
(min_ca, h_otrok, be_zh, no_moham, prabir)@ciise.concordia.ca
Agenda
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VOIP Introduction
What VOIP Clients Need?
What Service Providers Need?
Mechanism Design
Our Model
Our Algorithm and Example
Simulation Results and Future Work
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Acknowledgement
I would like to take this opportunity to express
our sincere gratitude to Professor Prabir
Bhattacharya and Mr. Hadi Otrok for the subject
of game theory. We special thanks for your time
and guidance. We had a lot of fun in
doing this project.
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What is Voice Over Internet Protocol
1. A protocol optimized for the
transmission of voice through the Internet
or other packet switched networks.
2. By 1973, voice was being transmitted
over the early Internet
3. The ability to transmit more than one
telephone call over the same broadband
connection
4. Conference calling, call forwarding,
automatic redial, and caller ID
5. Location independence
6. Integration with other services
available over the Internet
7. video conversation, message or data
file exchange in parallel with the
conversation, audio conferencing
Figure quote from wikipedia
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VOIP Web Service Based Application
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VOIP Challenges
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Network Congestion
Denial of Service
Packet Loss
Available Bandwidth
Reliability
Security
Echo
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VOIP Congestion Problem
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What VOIP Clients Need?
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Connect to the services
Availability
Reliability
Quality of Service
Reasonable Price
Security
Confidentiality
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What Service Providers Need?
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Fair Bandwidth Usage
Availability
Security
Quality of Service
Reputation
User Participation
Mechanism to Control the Traffic
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Challenges of Our Model
• How to motivate selfish client to participate ?
– Incentive (Money Back)
• What the clients should reveal?
– Cost-of-Analysis
• How the incentive should be designed such that
truth telling is the dominant ?
– Mechanism design
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What is Mechanism Design?
• Mechanism Design is the subfield of game theory.
• It uses game theory tools to achieve desired goal.
• The main deference between game theory and
mechanism design is the following:
– Game theory can be used to study what could happen when
independent players act selfishly/maliciously.
– Mechanism design allows a game designer to define rules in
terms of the Provider Object Function(POF) such that
players will play according to these rules.
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Mechanism Design
• Assume that participants are rational:
– Has a set of strategies
– Have a well defined valuation function over the possible
outcomes
– Will always act in a way that maximizes their utility
• We as designers wish to optimize some common
aggregated goal.
• It considers how to implement good system-wide
solutions to problems that involve multiple selfinterested agents with private information.
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Incentive Compatible Mechanism
• A mechanism determines as output and also charges payments
from the participants.
– Utility = Value (outcome)- payment
Example: In an auction for a single-item, the outcome defines
the allocation, and the payment for the winner. Assuming that
agent i has value vi = $10 for the item, then its utility for an
outcome is, ui = vi - p = 10 - p, and the agent has positive
utility for the outcome so long as p < $10
• A mechanism is incentive compatible (=Truthful=strategy
proof) if payments provide incentive to all participants to
always truthfully report all private information.
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Mechanism Design
θ1
...
Player 1
p1
θn
v1 (θi)
Player n
vn (θi)
pn
Mechanism computes payment and
outcome
The Provider Object Function
• Mechanism designs the payment such that truth telling is the
dominant strategy. This is done by giving the nodes a fixed
payment independent of the node’s declaration.
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Summary
• The mechanism asks users to report their private information.
• Based on the information, mechanism computes an output and
a payment which is strategy proof.
• The goal is to design a strategy proof mechanism where each
player selects the strategy truthfully to maximize its utility.
• Knowing that, there is no reason for users to report their true
types!
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Our Contributions
• Solve the congestion issue in a fair and effective way by
allowing users input their best strategies. Server selects users
based on the users’ strategies to allocate the resource to the
qualified candidates.
• Improve the VOIP system performance using a check
method, to allow the remaining available resource allocated
to the second best users so that the system can maximize the
active online candidates.
• We allow users to place their strategies according to their
selfish reasons which maximize the users’ benefits.
• Server selects users based on the users’ cost of analysis
function which maximizes the users’ benefits.
• Our payment methods based on the VCG mechanism
encourages users to participate in the game and increase
their loyalty to the service providers.
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Mechanism Design Model
• User Model <K, Si, Ui >
• K is a finite set of K users
• Each player i K has a non empty finite set of strategies(Si)
• Each player i K has a utility function Ui
Ui(Si) = Ci(Si, o) − Paymenti
• Server Model Provider Objective
Function
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VOIP Bandwidth and QoS model
•Total packet size =
(L2 header: MP or FRF.12 or Ethernet)+ (IP/UDP/RTP
header) + (voice payload size)
•PPS(Packets Per Second) =
(codec bit rate) / (voice payload size)
•Bandwidth = total packet size * PPS
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International Telecommunication
Union(ITU)
ITU-T Recommendation (User Strategy 1)
Median of
Score
Quality of Service
5
Excellent; Complete relaxation possible
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Good Attention necessary
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Faire Moderate effort requires
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Poor Considerable effort required
1
No meaning understood with any feasible effort
ITU E-Model
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User Strategy
• Price Unit they are willing to pay
Quality
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Our Payment Function
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Our Algorithm
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Our Example
ID
Strategy
Price MOS
Cost
Benefits
Payment
POF
167.24
10
Selectio
n
1
180
4.1
2.064
12.76
2*
166
4.1
1.90
0
3
200
4.1
2.29
25.09
174.91
8
S
4
66
3.9
3.01
25.84
40.16
2
S
5
126
3.85
2.28
47.35
108.65
9
S
6(*)
41
3.9
1.87
0.876
40.124
13
7
60
3.9
2.73
19.71
40.29
3
S
8
49
3.9
2.37
11.83
37.17
7
S
9
40
3.9
1.83
0
0
14
10
81
3.61
2.56
19.49
61.51
5
S
11
55
3.9
2.51
14.89
40.11
6
S
12
80
3.9
3.65
39.85
40.15
1
S
13
57
3.9
2.60
16.86
40.14
4
S
14
43
3.9
1.96
2.85
40.15
11
S
15
35
3.9
1.6
0
0
15
0
S
12
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Simulation Results(1)
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Simulation Results(11)
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Simulation Results(1I1)
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Future Work
• Develop a multiple service providers model
• Use data mining technique to helps users to
determine the price and quality with multiple
service providers
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Thank you !
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