1. FlowSense: Monitoring Network Utilization with Zero Measurement Cost Curtis Yu 1, Cristian Lumezanu 2, Yueping Zhang 2, Vishal Singh 2, Guofei Jiang 2, Harsha V. Madhyastha 1 1 UC Riverside, 2 NEC Labs America

2. SDN enables centralized control 2

3. A B SDN enables reactive control of network 3 C

4. State-of-the-art measurement  Active measurements  Injection of probes  Passive measurements  Expensive instrumentation and infrastructure setup  SDN measurements  Additional control traffic 4

5. FlowSense: measuring with zero cost  Leverage existing control traffic to measure network  No additional traffic introduced  Network informs system of changes  As accurate as switch polling 5

6. OpenFlow overview Flow Arrival: 1) Packet of new flow arrives 2) PacketIn message sent 3) FlowMod message sent 4) New rule installed Flow Completion: 1) Rule expires 2) Remove rule 3) FlowRemoved message sent 6 RuleMatchOutput 1Greensw2 RuleMatchOutput sw1sw2

7. Messages have utilization info  PacketIn  Signals new flow on port (t 1 )  FlowRemoved  Duration of entry in flow table (10s)  Amount of traffic matched (400 MB)  Can infer utilization contributed by flow on link 7 t1t1 t 1 + 10s Flow: PacketIn FlowRemoved

8. t1t1 t2t2 t3t3 t4t4 t5t5 t6t6 Time Estimating utilization in FlowSense 8 f1f1 f2f2 f3f3 CheckpointFlows LeftTotal UtilizationCheckpointFlows LeftTotal Utilization t4t4 240 MB/s CheckpointFlows LeftTotal Utilization t4t4 150 MB/s t5t5 110 MB/s CheckpointFlows LeftTotal Utilization t4t4 070 MB/s t5t5 030 MB/s t6t6 020 MB/s

9. FlowSense system design  Parser  Captures and analyzes control traffic  Utilization Monitor  Runs FlowSense algorithm  Utilization Table  Database of checkpoints 9

10. Evaluating FlowSense  Goals  Accuracy  Timeliness  Dataset  Testbed of NEC OpenFlow switches  Real-world traffic trace from a campus network switch 10

11. Accuracy testbed 11  1 continuous flow  3 separate short flows

12. FlowSense is as accurate as polling 12

13. Revisiting utilization estimation 13 t1t1 f1f1 f2f2 f3f3 t2t2 t3t3 t4t4 t5t5 t6t6 Time CheckpointFlows LeftTotal Utilization t4t4 240 MB/s CheckpointFlows LeftTotal Utilization t4t4 070 MB/s t5t5 030 MB/s t6t6 020 MB/s

14. Perfect utilization information is typically delayed 14

15. Coarse-grained estimation can be obtained soon 15

16. Data refreshes in the order of seconds 16

17. Conclusion  FlowSense  Leverage control traffic to estimate utilization  Incurs no measurement cost  Estimates are accurate  Comparable to switch polling  Data is timely  Do not have to wait too long for new utilization information 17

18. Future work  Measuring long flows  Overhead of stopping the rule for measurement  Wildcard and proactive rules  Reasonable way to merge active measurements to keep overhead low  Link Latency  Similar method to enable zero cost measurement of latency 18

19. Questions? 19