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

SDN enables centralized control 2

A B SDN enables reactive control of network 3 C

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

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

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

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 s Flow: PacketIn FlowRemoved

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

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

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

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

FlowSense is as accurate as polling 12

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

Perfect utilization information is typically delayed 14

Coarse-grained estimation can be obtained soon 15

Data refreshes in the order of seconds 16

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

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

Questions? 19