On Controller Performance in Software-Defined NetworksAuthor: Amin Tootoonchian, Sergey Gorbunov, Yashar Ganjali, Martin Casado and Rob SherwoodPublisher: Presenter: Yu Hao, TsengDate: 2013/05/29

Outline• Introduction• NOX-MT• Experiment Setup• Controller Throughput• Controller Response Time• Cbench

Introduction• How fast can the controller respond to data path requests?• How many data path requests can it handle per second?• For example : • NOX handles around 30k flow initiation events per second while

maintaining a sub-10ms flow install time [14].• Kandula et al. [9] found that a 1500-server cluster has a median

flow arrival rate of 100k flows per second.• Benson et al. [2] show that a network with 100 switches can have

spikes of 10M flows arrivals per second in the worst case.• We present NOX-MT a publicly-available multithreaded

successor of NOX.

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NOX-MT• NOX is not optimized for performance and is single-threaded.• The techniques to optimize NOX are including : • I/O batching to minimize the overhead of I/O• Port the I/O handling harness to Boost Asynchronous I/O (ASIO)

library• Use a fast multiprocessor-aware malloc implementation

• NOX-MT is far from perfect.• Heavy use of dynamic memory allocation and redundant memory

copies on a per-request basis• Using locking were robust wait-free alternatives exist

Experiment Setup• Cbench emulates a configurable number of OpenFlow

switches that all communicate with a single OpenFlow controller.

• Each emulated switch sends a configurable number of new flow messages to the OpenFlow controller, waits for the appropriate flow setup responses, and records the difference in time between request and response.

• Cbench supports two modes of operation : • Latency• Throughput

Controller Throughput• Maximum throughput

Controller Throughput (Cont.)• Relation with the number of active switches

Controller Throughput (Cont.)• Relation with the load level

Controller Throughput (Cont.)• Effect of write-intensive workload

Controller Response Time• Minimum response time• Average response times of all controllers are between 100 and 150

microseconds.• Maximum response time

Controller Response Time (Cont.)• Relation with the load level

Controller Response Time (Cont.)• Relation with the number of active switches

Cbench

Cbench (Cont.)

Cbench (Cont.)• http://www.openflow.org/wk/index.php/Controller_Performance_Comparisons

Cbench (Cont.)responses/s min max avg stdev

NOX 42620.00 232301.74 203830.60 57337.18

POX 7764.75 7939.25 7875.25 54.54