Load Balancing in Protection Switching of Optical Networks

1. Load Balancing in Protection Switching of Optical Networks Hongkyu Jeong, Gyu-Myoung Lee Information and Communications Univ. (ICU) Student ID : 20022130, 2000520 E-mail: paul@icu.ac.kr, gmlee@icu.ac.kr

2. Outline • Introduction • Proposed Path Selection • Mechanism • Simulation Assumptions • Numerical Results and Analysis • Conclusion and Future Works • References

3. Introduction • Traffic of multimedia data has been increasing • Survivability of optical network has become one of the pivotal issues • In the real world, 1+1 or 1:1 protection mechanism commonly has been adopted • Resource utilization of those protection schemes is at most 50% low when applied to optical networks • Sharing rate of backup path is noticeably low • Recently, traffic engineering concept of GMPLS is introduced • Improvement on network resource utilization through load-balancing is becoming the important issue

4. Introduction (cont.) • Analyze four path selection models • Preconfigured protection scheme • Assumption • Load is the call request to reserve wavelength for working path (WP) and backup path (BP) • Achieve higher utilization rate of BP • By introducing the concept of load-balancing where selecting policies are adopted for models • Achieve 100% restoration • By not selecting the BP that has the WP within the same SRLG

5. Proposed Path Selection Mechanism • First, find shortest path set • Second, select three disjointed shortest paths in the shortest path set by each specific policy • Most shortest path is used for WP • If there are call requests which have same source node and destination node pair, same paths are used for reserving WP and BP • Third, when a call request is arrived at a source node, the node finds a wavelength for WP • Reserve or reject Fig.1 Simplified flow of proposed mechanism

6. Proposed Path Selection Mechanism (cont.) • Fourth, nodes preferentially finds a wavelength for BP which can be shared • If there is no sharable wavelength, unused wavelength is reserved for BP • If there is no unused wavelength, the call request is rejected • Only when it is possible to reserve both WP and BP • Call request is accepted and wavelength reserving mechanism is completed Fig.1 Simplified flow of proposed mechanism

7. Simulation Assumptions Table 1. path selection policies of four different models • Find shortest path set from a node to other node • Select shortest paths for WP and BP by the policy of each model • For the selected model, case 1 and case 2 are alternately selected as shown in Table 1

8. Simulation Assumptions (cont.) • Each link capacity (W) • Unlimited in the case of evaluating sharing rate • 32 and 64 wavelengths are used to evaluate the call request blocking rate • The number of node N is 16 • Call request is 8*load (load is positive integer) • Each node has no wavelength converter • WP and BP are disjointed path • When we look for a sharable wavelength for BP, the wavelength should not be shared by BPs that have the WP which belongs to the same SRLG

9. Simulation Assumptions (cont.) • Torus topology (Fig.2) • It has not only many paths but also similar lengths (number of nodes to be passed) from a source to a destination • Similar characteristics which topologies in the real world possess • For each call requests, the WP and BP are randomly chosen from the shortest path set • For each experiment we run 50 times simulation, and then take the average Fig.2 A 2-dimensioinal 4X4 Torus Toplogy

10. Simulation Assumptions (cont.) • Sharing rate: , where : Accepted request for reserving BP : Wavelength used for reserving BP • Blocking rate: , where : Number of call requests : Number of accepted call requests

11. Numerical Results and Analysis • Fig.3 • Shows model 2,3, and 4 which adopt load-balancing scheme manifest higher sharing rate compared to model1 which does not adopt the load-balancing scheme • Shape of graph is regular at each model • Sharing rate of model 4 • Improved on average 30% compared with that of model 1 Fig.3 Backup Path Sharing Rate of model 1~4

12. Numerical Results and Analysis (cont.) • Fig.4 (W=32) • Model 2,3, and 4 have lower blocking rate than that of model 1 • Model 4 has average 23% lower blocking rate • Achieve higher network throughput • Expectation: growing load balancing effect • More nodes, links, and wavelengths per link Fig.4 Call Request Blocking Rate of model 1~4

13. Numerical Results and Analysis (cont.) • Fig. 5 (W=64) • Improved load balancing effect by doubling the number of wavelengths to 64 • Model 4 shows 26% lower blocking rate on average than that of model 1 Fig.5 Call Request Blocking Rate of model 1~4

14. Conclusion and Future works • Introduce the concept of load balancing into protection mechanism • Achieve 30% higher sharing rate and 23% (w=32), 26% (w=64) lower blocking rate compared to the commonly used 1:1 protection mechanism (model 1) • Maintain 100% restoration capability • Future Works • Apply proposed mechanism to various mesh topologies • Use the concept of threshold in order to enhance the positive effect of load balancing

15. References [1] Ayan Banerjee et al. “Generalized Multiprotocol Label Switching: An Overview of Signaling Enhancements and Recovery Techniques”, IEEE Communication Magazine, July 2001 [2] Ayan Banerjee et al. “Generalized Multiprotocol Label Switching: An Overview of Routing and Management Enhancements”, IEEE Communication Magazine, Jan. 2001 [3] S. Ramamurthy and Biswanath Mukherjee, “Survivable WDM mesh networks, partⅠ – protection”, INFOCOM ’99, March 1999, Page(s): 744 -751 vol.2 [4] <draft-many-inference-srlg-00.txt>, IETF draft

16. Thank you !Q & A