1. Routing and Wavelength Assignment in Wavelength-Convertible Waveband-Switched Networks Routing and Wavelength Assignment in Wavelength-Convertible Waveband-Switched Networks Fang-Sheng Lin* Ching-Fang Hsu Te-Lung Liu

2. Outline • Introduction • Related Work • Reconfigurable MG-OXC architecture • Waveband Assignment with Path-Graph (WAPG) algorithm • The Proposed Scheme • Problem Definition • Least-Configuration with Bounded Conversion (LCBC) algorithm • Performance Evaluation • Conclusions

3. Introduction (1/5) • Owning to the development of DWDM systems, the number of wavelengths gets larger and larger. • Traditional OXCs which switch traffic only at wavelength granularity will need a great deal of wavelength ports. • higher complexity • difficulty associated withcontrollingand management of such large OXCs

4. Introduction (2/5) • The main idea of Waveband Switching (WBS) is to aggregate a set of wavelengths into abandand switch the band using a single port whenever possible.

5. Introduction (3/5) • The wavelength continuityconstraint on lightpath establishment existing in wavelength routed networks also apply to WBS networks. • One possible way to relax the wavelength continuity constraint is to use wavelength converters at the switching node.

6. Introduction (4/5) • It is more practical and cost-effective to share a set of limited range wavelength converters at each node.

7. Introduction (5/5) • Focused on sub-pathgrouping strategy, we proposed a new heuristic algorithm to solve the dynamic RWA problem of wavelength-convertible WBS networks efficiently.

8. BXC Wavelength Conversion Bank WXC BTW WTB WXC Layer … … … … … … βY BXC Layer BTF FTB … … Y … … … … FXC Layer αX FXC X … … Related Work (1/4) - Reconfigurable MG-OXC • The Multi-granular Optical Cross-Connect (MG-OXC) architecture with wavelength conversion bank [1]

9. Related Work (2/4) - Reconfigurable MG-OXC • There is a unique issue related to using wavelength converters: • In WBS networks, an instantiation of wavelength conversion requires all wavelengths in a waveband to be de-multiplexed and results in extra ports consumption. • Hence, inefficient banding and employment of wavelength converters may cause more blocking of future requests due to the limitation of the OXC ports.

10. Related Work (3/4) - WAPG algorithm • The authors in [1] proposed a heuristic algorithm called Waveband Assignment with Path-Graph (WAPG) to address the effect on the blocking performance and efficient usage of wavelength converters in WBS networks.

11. Related Work (4/4) - WAPG algorithm • WAPG • Find out a wavelength-continuous path similar First-Fit algorithm first. • If no wavelength-continuous path can be found, find a non-wavelength-continuous path using minimum number of converters. • However, it may cause undesired port usage.

12. The Proposed Scheme (1/5)- Problem definition • The network topology • G=(V, E) • Each fiber link has W wavelengths, which are partitioned into B uniform wavebands. • According to the index continuity, a fixed number K of wavelengths are chosen to be grouped into a band

13. The Proposed Scheme (2/5)- Problem definition • For the wavelength-convertible WBS networks, the major objectives of dynamic RWA problem include • to minimize the configuration (switching) cost, i.e., the total number of ports used, • to utilize wavelength conversion in a most efficient manner, and • to achieve a magnificent network performance at the same time.

14. The Proposed Scheme (3/5)- Least-Configuration with Bounded Conversion • We proposed a new heuristic algorithm, called Least-Configuration with Bounded Conversion (LCBC), based on • the fixed routing algorithm, • the layered graph approach, and • a well-designed cost function

15. Layer 0 transmission edge Layer 1 conversion edge Layer 2 Layer W-1 The Proposed Scheme (4/5)- Least-Configuration with Bounded Conversion …. An illustration of layered graph modeling

16. The Proposed Scheme (5/5)- Least-Configuration with Bounded Conversion • The proposed cost function Wavelength conversion degree The weight factor The extra port consumption at node v while λ is the input channel and λ' is the output channel [9] Link capacity ψ= 0, no wavelength conversion performed 1, wavelength conversion occurred

17. Performance Evaluation (1/4) • USAnet • 46 nodes and 76 links. • Every node is assumed to be a MG-OXC. • Adopting the share-per-node architecture • 25 wavelengths converters per node

18. Performance Evaluation (2/4) • Traffic pattern • A Poisson process with mean γ • Exponentially distributed connection duration time whose mean is 1 time unit • All existing connections can not be rearranged.

19. Performance Evaluation (3/4) 93.8% 3.8% β vs. blocking probability (W=80, K=10)

20. 26% 51.1% 97.8% Performance Evaluation (4/4) Blocking probability vs. arrival rate (W=80, K=10, β=0.75)

21. Conclusions (1/2) • In this paper, we proposed a heuristic algorithm, named LCBC, to solve the problem of dynamic RWA in wavelength-convertible WBS networks. • Adopting fixed routing as the routing selection algorithm, we transform the wavelength selection problem into an equivalent shortest-path problem in an auxiliary graph. • Moreover, we proposed a cost function to calculate an appropriate weight to each edge, such that limited resource, including BTW/WTB ports and wavelength converters, could be utilized more efficiently.

22. Conclusions (2/2) • To investigate the efficiency, we developed the simulation to observe the performance of LCBC and that of WAPG with various β, and conversion degree. • LCBC can achieve much significant blocking performance gain.

23. Thank you!