1. Recovery Time of Degraded Throughput in Best-Effort CWDM Networks with ROADMs Graduate School of Engineering, Osaka Prefecture University, Japan Shogo Kawai

2. 2 Contents Introduction Experimental IP-over-CWDM Network with ROADMS Recovery Time of Degraded Throughput When Removing Congestion Congestion Removing by Adding a Lightpath Congestion Removing by Adding a Static Bypass Route Conclusion

3. 3 Introduction Rapid increase of traffic demands Network types Optical LAN, Campus networks and factory networks CWDM technologies are effective No wavelength stability control The devices are low cost Important tasks by the network administrators Avoid traffic congestion The demand changes

4. 4 ROADM (Reconfigurable Optical Add/Drop Multiplexer) Optical couplers and splitters The wavelength number was limited We proposed stackable ROADM (S-ROADM) [5] Evaluate the traffic congestion removing performance Lightpath reconfiguration IP routing reconfiguration [5] Md. Nooruzzaman, Y. Harada, O. Koyama, and Y. Katsuyama, Proposal of stackable ROADM for wavelength transparent IP-over-CWDM networks, IEICE Trans. Commun, vol. E91-B, No.10, pp. 3330-3333, 2008.

5. 5 Performance required to the Network SLA (Service Level Agreement) Transmission services should satisfy SLS (Service Level Specification) Performance parameters throughputs, delay, packet loss, connection setup time, service availability, routing stability and recovery time User classifications[10] Premium, Gold, Silver and Bronze When the Ethernet-based IP transmissions are assumed in the IP-over-CWDM network, the service level class belongs to Bronze

6. 6 Experimental IP-over-CWDM Network with ROADMS S-ROADM Common- ROADM with couplers and splitters ROADM Optical Trancivers Layer 3 Switch

7. 7 Recovery Time of Degraded Throughput When Removing Congestion The congestion removing performance Recovery time to keep throughput The recovery time is 10s for Bronze users [10] IP Packets are routed by OSPF (Open Shortest Path First) CS (Control System) connected to Node1 monitor the port throughput of the L3SWs send control signal to ROADMs and L3SWs 2 possibilities Lightpath reconfiguration by ROADMs IP routing reconfiguration

8. 8 Congestion Removing by Adding a Lightpath Lightpath set LS 0 Only one direct lightpath L2 connects Node1 and 3 congestion occurs in L2 L11 and L12 are reconfigured to make L11 If the traffics can be transmitted without L11 and L12 (a) Lightpath set LS 0 (b) Lightpath set LS 1

9. 9 Experimental Results Packet Stream S1 TX1(Node1) Rx1(Node3) Increased by 0.1Gbps every 5s Packet Stream S2 Tx2(Node1) Rx2(Node3) 0.5Gbps (constant) Threshold 0.95Gbps A1(L2)=1Gbps Control signal sent by CS Congestions were removed A1(L2)=0.5Gbps=S2 A2(L11)=S1 The routing for S1 was changed by the CS Total throughput sent from Node1=1.1Gbps Total throughput received at Node3 = 1Gbps Congestion occurred Single lightpath had a bit rate of 1Gbps

10. 10 Congestion Removing by Adding a Lightpath After the control signals were observed It took 8s on a packet detection base to remove the congestion, includes the establishing time by OSPF. 10s after the port throughput exceeded the threshold The congestion related time was 10s at longest The recovery time specified for Bronze users

11. 11 Congestion Removing by Adding a Static Bypass Route Streams S1 and S2 Congestion occurs in L2 The routing for S2 is changed so as to send S2 through a bypass route Sending a file containing the commands to add the destination, nexthop, and the preference to the L3SWs

12. 12 Experimental Results S1 : Increased by 0.2Gbps S2 : Constant at 0.2Gbps Control signal sent Static bypass route was created Total throughput received at Node 3 was below 1.1Gbps The routing for S2 was changed Congestion occurred in L2 for about 3s

13. 13 Conclusion Congestion removing performance has been investigated and examined in an experimental 5-node IP-over-CWDM network with S-ROADMs By adding a new lightpath can provide effective adjustment of large traffic By adding a static bypass route can provide fine granularity adjustment of traffic It is found that the congestion related time was 10 s at longest, which is equal to the recovery time specified by the SLA Thus, the S-ROADMs enable us to keep the throughput by the lightpath reconfigurations or adding a static bypass route within the recovery time by the SLA Further Study : the recovery time depends on the traffic pattern, the control procedures and others, requiring further study to satisfy the SLA in more general traffic