1. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 1 Virtual Topology  Wavelength routed network  Lightpath = a direct connection between nodes.  Physical topology  Virtual topology

2. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 2 VT Design  Given  Physical topology G(V,E)  Traffic intensities between nodes.  Find  Lightpaths to be set-up.  Virtual topology  Objective  Maximize traffic load.  Minimize cost.

3. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 3 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.

4. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 4 Illustrative Example 0 1 2 3 0 0 1 0 0 1 0 0 1 0 2 0 0 0 1 3 1 0 0 0 0 1 2 3 0 0 0 0 1 1 1 0 0 0 2 0 1 0 0 3 0 0 1 0 0 1 3 2 0 1 3 2 0 1

5. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 5 Motivation  Backbone network  Slow changes in traffic  Change the virtual topology slowly. t 1 t 2

6. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 6 Earlier Approaches  Wait until VT becomes inefficient.  Run an optimization algorithm  new VT.  Run a transformation algorithm. Old VT New VT  Branch-exchange method

7. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 7 Our Approach  Observe the traffic Adapt VT  New VT adjacent to old VT: Only 1 lightpath is different.  Simple reconfiguration.  Simple transition. continuously.

8. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 8 Optimization Goals  Using minimum number of lightpaths.  Load balancing.  Minimizing the number of changes:  transition period’s length  traffic rerouting

9. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 9 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

10. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 10 Implementation  Traffic loads on links are observed periodically: Observation period T.  T should be small enough to follow the changes.  Typically few 100s

11. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 11 Adaptation Algorithm Start with initial topology. Every T seconds do: Compare the load L i on each lightpath i with the watermarks. if L i > W H then add an appropriate lightpath. else if L i < W L then delete an appropriate lightpath. else do not adapt the VT.

12. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 12 MILP  Objective: Minimize L max  Constraints: (1)

13. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 13 MILP (cont.)  Constraints: if L max > W H then if L min < W L then (2)

14. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 14 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.

15. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 15 Results (MILP) N = 6 W = 4 Tx = 4 W H = 0.8

16. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 16 Results (MILP)

17. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 17 Results (Heuristic)

18. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 18 Results (Heuristic)

19. Virtual Topology Adaptation in WDM Mesh Networks (for ECS 259: A. Gencata and B. Mukherjee, UC Davis) 19 Results (Heuristic)