1. Bidirectional Optical Ring Network Having Enhanced Load Balancing and Protection Dzmitry Kliazovich, Fabrizio Granelli, University of Trento, Italy Copenhagen, Denmark May 22, 2006 Hagen Woesner (woesner@create-net.it) CREATE-NET ONDM 2006

2. Hagen Woesner (woesner@create-net.it) May 22, 2005 Outline Introduction  Last Mile and Metropolitan Networks Traffic Aggregation Core  Network and node architectures  MAC Protocol Candidates  Resilience and Load Balancing Strategies Comparison and Conclusions

3. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Last Mile Networks Which technology will drive Access in networks? FTTx became economically feasible  Up to 100 Mb/s per user Passive Optical Networks  PON (A/B/E/GPON): total bitrate 155 Mb/s and 2.5 Gb/s  SuperPON: 10 or 40 Gb/s Optical transmission is required Switching inside OLT can be done electronically

4. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Metropolitan Area Network (MAN) Traffic Aggregation in Metro Area  Switching and Routing becomes a Communication and Computing Bottleneck!

5. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Traffic Aggregation Core Perform Distributed Switching Shared medium (bandwidth) Drop-and-Continue principle to avoid OEO conversion and corresponding processing Bidirectional Communications Ref.: A. Gumaste and I. Chlamtac, "Light-trails: a novel solution for IP-centric communication," in Workshop on High Performance Switching and Routing (IEEE, New York, 2003). Ref.: D. Kliazovich, F. Granelli, H. Woesner, and I. Chlamtac, “Bidirectional Light- Trails for Synchronous Communications in WDM Networks”, GLOBECOM'05, St. Louis, US, December 2005.

6. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Traffic Aggregation Core Bidirectional Optical Ring Client Node Drop-and-Continue using Optical Couplers

7. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Traffic Aggregation Core Hub-and-spoke Architecture Virtual Link Break creates Two Dual Buses on a bidirectional optical ring allowing spatial reuse Each bus is running OTDM  HUB communicates at full bus speed (100 or 160 Mb/s)  Client node receives/transmits in a single time slot (10 Mb/s) Downstream: point-to-multipoint Upstream: multipoint-to-point Terminates eastern bus downstream Terminates western bus downstream

8. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Hub Node Architecture High-speed transmitters and receivers  Implemented using Short Pulse Lasers (5 - 10 us)

9. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Client Node Architecture Low-cost requirement  Minimum number of transmitters and receivers

10. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Network Initialization Discovery Topology  Hub goes around the ring configuring client nodes in “path-through” mode Place Virtual Link Break  Assume uniform network load initially  Divide ring into two equal by the number of nodes dual buses Assign Home Channels  Client node listens a certain OTDM channel in downstream  Several nodes can share a single channel

11. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Network Communications Point-to-multipoint Downstream reserved for reception Multipoint-to-point Upstream requires contention resolution to ensure collision-free medium access No node is allowed to transmit if the bus is not idle (medium sensing module) – CSMA/CA However CSMA/CA in light trails leads to Unfairness  It always favors the nodes located closer to the beginning of the upstream bus

12. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 MAC Protocol Candidates Reservation-based MAC  Client sends bandwidth request in the upstream  Hub computes a fair share  Bandwidth is granted via downstream Good Fairness (depends on scheduler) Large Reservation-Grant Delay  At least double propagation time between Hub and Client node  Depends of the node relative position with the bus A good candidate for constant bandwidth provisioning  Example: dedicated channels for ISPs

13. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 MAC Protocol Candidates Token-rotation MAC  Tokens generated by Hub in the downstream are rotated into the upstream  Token detection requires optical correlator  Token extraction is done using overwrite operation Medium Access Delay tradeoffs with Round-trip propagation delay, Token rotation and Token holding time Network size defines Utilization and Performance Backpressure Control  CSMA/CA in Medium Access  Hub monitors node’s sending rates  Hub sends backpressure signal to the nodes sending above a fair share On-demand Medium Access

14. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Resilience and Load Balancing Key: Shift Virtual Link Break Single Link Failure or Node Malfunction Robustness  Complete shut down of optical functionality is considered  Distributed algorithm with no Hub coordination Load Balancing between busses  Triggered by Hub based on the bus utilization level

15. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Resilience and Load Balancing 1. Downstream clock and no upstream clock – turn into “loopback” mode 2. No downstream clock – join another bus by flipping optical switches. Then, send signal on the upstream 3. Being in “loopback” switch to “path-through” upon incoming signal on the upstream Tree rules of Distributed Resilience algorithm followed by nodes:

16. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Resilience and Load Balancing Link Failure CN 1 hearing clock on the downstream and no clock on the upstream closes western bus; Being isolated CN 2 and CN 3 try to join eastern bus and send in the upstream; CN 4 hearing an upstream signal turns off light terminator opening the downstream for CN 3 and CN 2 ;

17. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Related Works and Comparison

18. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Conclusions Optical Network Architecture for traffic aggregation in Metropolitan Area Network (MAN) which consists of two dual buses on a bidirectional ring fiber Low-cost Client node architecture MAC candidates: reservation-based, token- rotation or CSMA/CA with backpressure control Resilience strategy able to resolve single link break or node malfunction

19. ONDM 2006 Hagen Woesner (woesner@create-net.it) May 22, 2005 Thank you!