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
0
