FlowSense: Monitoring Network
Utilization with Zero Measurement Cost
Curtis Yu1, Cristian Lumezanu2, Yueping Zhang2, Vishal
Singh2, Guofei Jiang2, Harsha V. Madhyastha1
1UC
Riverside, 2NEC Labs America
SDN enables centralized control
2
SDN enables reactive control of
network
B
A
C
3
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
sw1
Flow Completion:
1) Rule expires
2) Remove rule
3) FlowRemoved
message sent
Rule
Match
Output
1
Green
sw2
sw2
6
Messages have utilization info
PacketIn
 Signals new flow on port (t1)
FlowRemoved
 Duration of entry in flow table (10s)
 Amount of traffic matched (400 MB)
Can infer utilization contributed by flow on link
t1
t1 + 10s
PacketIn
FlowRemoved
Flow:
7
Estimating utilization in FlowSense
Time
t1 t2 t3
t4
t5
t6
f1
f2
f3
Checkpoint
t4
Flows Left
2
1
0
Total Utilization
40 MB/s
50
70
t5
t6
0
1
0
30 MB/s
10
20 MB/s
8
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
 1 continuous flow
 3 separate short flows
11
FlowSense is as accurate as polling
Utilization (MBps)
60
Polling
FlowSense
50
40
30
20
10
0
0
50
100
150
Time Elapsed (sec)
200
12
Revisiting utilization estimation
Time
t1 t2 t3
t4
t5
t6
f1
f2
f3
Checkpoint
t4
Flows Left
0
2
Total Utilization
70 MB/s
40
t5
t6
0
0
30 MB/s
20 MB/s
13
Perfect utilization information is
typically delayed
Fraction of checkpoints
1
0.8
0.6
0.4
0.2
1
10
100
1000
Time until last active flow ends (s)
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