On The Interaction Between Overlay Routing and Underlay Routing

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On The Interaction Between Overlay Routing and
Underlay Routing

• Yong Liu, Honggang Zhang,
• Weibo Gong, Don Towsley

Presented by Honggang Zhang
Univ. of Massachusetts Amherst
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Motivation Interactions Between Application
Level Network and Physical Network

• physical network control
• routing, congestion control,

• add an overlay

• and another

• Result?
• interactions?
• controllers mismatch?

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Outline

• Problem Formulation
• Simulation Study
• Game-theoretic Study
• Conclusions

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Routing in Underlay Network

• Routing on physical network level
• Inter-domain BGP, etc.
• Intra-domain OSPF, MPLS, etc.
• determine routes for all source-destination
  traffic demand pairs
• minimize network-wide delay, cost, etc.

traffic demand pair A-gtB traffic demand pair
A-gtC traffic demand pair C-gtB
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Routing in Overlay Network
Overlay demand A-gtB logical routes A-gtC-gtB and
A-gtB

• An overlay network choose routes at application
  level to minimize its own delay or cost

C
A

• Overlay
• gains advantage
• better path delay, loss, throughput, etc
• is selfish
• potential performance degradation to other
  non-overlay traffic

B
C
D
E
A
B
demand pair A-gtC
demand pair C-gtB demand pair A-gtB
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Considering overlay and underlay together ?

• How do they interact with each other?
• How does selfish behavior of overlay routing
• affect overall network performance?
• affect non-overlay traffic performance?
• affect its own performance?

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Interactions Between Overlay Routing and
Underlay Routing
Overlay Routing Optimizer To minimize overlay
cost
Underlay Routing Optimizer To minimize overall
network cost
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Related Work

• On Selfish Routing in Internet-like
  Environments, L. Qiu, Y. R. Yang, Y. Zhang, and
  S. Shenker, ACM/SIGCOMM, August 2003
• "Can ISPs Take the Heat from Overlay
  Networks?,R. Keralapura, N. Taft, C. N. Chuah,
  and G. Iannaccone, ACM/HotNets-III, November
  2004

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Our Approach

• Focusing interaction in a single AS
• Considering two routing models for overlay and
  one routing model for underlay
• Simulating the interaction dynamic process
• Studying this process in a Game-theoretic
  framework

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Routing Models

• Overlay routing model
• Selfish source routing
• Individual user controls infinitesimal amount of
  traffic, to minimize its own delay
• Optimal overlay routing
• A central entity minimizes the total delay of all
  overlay traffic demands

• Underlay routing model
• Optimal underlay routing
• A central entity minimizes the total delay of all
  network traffic, e.g. Traffic Engineering MPLS

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Simulation Study Optimal Overlay and Optimal
Underlay
14 node tier-1 POP network (Medina et.al.
2002) bimodal normal model of traffic demand 3
overlay nodes
Node without overlay
Node with overlay
Link
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Simulation Study ( case 1 8 overlay traffic)
Optimal Overlay and Optimal Underlay

• Iterative process
• Underlay takes turn at step 1, 3, 5,
• Overlay takes turn at step 2, 4, 6,

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Simulation Study (case 2 10 overlay traffic)
Optimal Overlay and Optimal Underlay

• Iterative process
• Underlay takes turn at step 1, 3, 5,
• Overlay takes turn at step 2, 4, 6,

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Game-theoretic Study

• Two-player non-zero sum game

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Game-theoretic Study
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Optimal Underlay Routing v.s. Optimal Overlay
Routing

• Overlay
• One central entity calculates routes for all
  overlay demands, given current underlay routing
• Assumption it knows underlay topology and
  background traffic

X(k)
1-X(k)
We denote overlays routing decision with a
single variable X(k) overlays flow on path ACB
after round k
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Best-reply Dynamics

• There exists unique Nash equilibrium x,
• x globally stable x(k) ?x, from any initial
  x(1)

When x(1)0, overlay performance improves
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Best-reply Dynamics

• There exists unique Nash equilibrium x,
• x globally stable x(k) ?x, from any initial
  x(1)

When x(1)0.5, overlay performance degrades
Overlay Delay Evolution
Overlay Routing Evolution
Underlays turn
delay
Overlays turn
x(k)
BAD INTERACTION!
x(k)gtx(k1)gtx
x
x(k)ltx(k1)ltx
Round k
Round k
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Conclusions Open Issues

• Selfish overlay routing can degrade performance
  of network as a whole
• Interactions between blind optimizations at two
  levels may lead to lose-lose situation
• Future work
• larger topology analysis/experimentation
• overlay routing and inter-domain routing
• interactions between multiple overlays
• implications on design overlay routing
• regulation between overlay and underlay

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Thank you!Questions?