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VT Reconfiguration. Traffic is dynamic : Traffic intensities change in time.  VT may be inefficient for new traffic. Problem : How can we change the VT to accommodate the new traffic intensities? Solutions : Redesign the VT. Change some lightpaths  Reconfiguration.

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vt reconfiguration
VT Reconfiguration
  • Traffic is dynamic: Traffic intensities change in time. VT may be inefficient for new traffic.
  • Problem: How can we change the VT to accommodate the new traffic intensities?
  • Solutions:
    • Redesign the VT.
    • Change some lightpaths  Reconfiguration.

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

illustrative example

0 1

0 1

3 2

3 2

Illustrative Example

0 1

0 1 2 3

0 0 1 0 0

1 0 0 1 0

2 0 0 0 1

3 1 0 0 0

3 2

0 1 2 3

0 0 0 0 1

1 1 0 0 0

2 0 1 0 0

3 0 0 1 0

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

motivation
Motivation
  • Backbone network
    • Slow changes in traffic Change the virtual topology slowly.

t1 t2

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

earlier approaches
Earlier Approaches
  • Wait until VT becomes inefficient.
  • Run an optimization algorithm  new VT.
  • Run a transformation algorithm.Old VT New VT
    • Branch-exchange method

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

our approach
Our Approach
  • Observe the traffic Adapt VT
  • New VT adjacent to old VT: Only 1 lightpath is different.
  • Simple reconfiguration.
  • Simple transition.

continuously.

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

optimization goals
Optimization Goals
  • Using minimum number of lightpaths.
  • Load balancing.
  • Minimizing the number of changes: transition period’s length traffic rerouting

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

main idea
Main Idea
  • Add or delete 1 lightpath at a time.
  • Add a lightpath if some lightpaths are heavily loaded.
  • Delete a lightpath if some lightpaths are lightly loaded.
  • 2 parameters:
    • High watermark
    • Low watermark

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

implementation
Implementation
  • Traffic loads on links are observed periodically:Observation period T.
  • T should be small enough to follow the changes.
    • Typically few 100s

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

adaptation algorithm
Adaptation Algorithm

Start with initial topology.

Every T seconds do:

Compare the load Li on each

lightpath i with the watermarks.

ifLi > WHthen

add an appropriate lightpath.

else ifLi < WLthen

delete an appropriate lightpath.

else

do not adapt the VT.

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

slide10
MILP
  • Objective: Minimize Lmax
  • Constraints:

(1)

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

milp cont
MILP (cont.)
  • Constraints:

if Lmax > WH then

if Lmin < WL then

(2)

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

comparison
Comparison
  • We compare MILP to a full-reconfiguration method.

Start with initial topology.

Every T’ seconds do:

Find the minimum #lightpaths for the

new traffic pattern.

Find the virtual topology such that:

It has minimum #lightpaths.

It requires minimum #changes from

the previous topology.

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

results milp
Results (MILP)

N = 6

W = 4

Tx = 4

WH = 0.8

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

results milp1
Results (MILP)

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

results heuristic
Results (Heuristic)

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

results heuristic1
Results (Heuristic)

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)

results heuristic2
Results (Heuristic)

Virtual Topology Adaptation in WDM Mesh Networks

(for ECS 259: A. Gencata and B. Mukherjee, UC Davis)