Efficient Gigabit Ethernet Switch Models for Large-Scale Simulation Dong (Kevin) Jin David Nicol Matthew Caesar University of Illinois at Urbana-Champaign

Introduction and Motivation Gigabit Ethernet Widely implemented low-level network technology Backbones of many large scale networks –Power grid control networks Modbus, DNP3, protocols can run on top of Ethernet frames –Data centers –Metro area deployment Frame delay and loss mainly caused by switches 2

Introduction and Motivation Lab Testbed with Real Devices 3 Ethernet Switch Relay SEL 421 Data Aggregator SEL 3351 Control Station Historian

Introduction and Motivation 4

Switch Model Requirements Fast simulation –With embedded real devices test-bed simulation must run faster than real time Accuracy in latency and frame loss prediction that is sufficient for studies of applications and protocols running on the network Straight forward model development for new switches 5

Ethernet Switch Three basic components: buffer, processor and switching fabric Different scheduling policy first come first serve (FCFS), round robin (RR), fair queueing(FQ), weighted round robin (WRR) … Different buffering strategy Shared buffering, input queueing, output queueing, virtual output queueing … 6

Approach 7 1. Perform Experiments on real switches 2. Build Analytical models 3. Build Simulation models in RINSE 4. Evaluate Simulation Speed and Accuracy

Measurement Test-bed Requirement Generate traffic up to line rate with user configured parameters such as frame size, sending rate and inter- frame gap Record frame delays and arrival orderings with microsecond resolution Capture frames at line rate with little loss 8

Measurement 9

10 Single flow Constant Bit Rate Raw Ethernet frames Input rate: 100Mb/s to 1Gb/s

Measurement 11 3COM NetGear Two flows Constant Bit Rate Raw Ethernet frames Each input rate: 100Mb/s to 1Gb/s

Queueing Models 12 NetGear, FCFS 3COM, WRR

Queueing Models 13 3COM Real Queuing Model NetGear Real Queuing Model

Latency-Approximate Model WRR queueing model –One event per frame arrival per switch –One per scheduling round per switch Latency-Approximate WRR model –One event per frame per switch –Upon frame arrival accurate determine if the frame will be dropped estimate latency based on past delay –Not managing the explicit queueing of frames 14

Latency-Approximate Model 15

Lantency-Approximate Model 16 3COM Real Lantency-Approximate WRR Model

Model Evaluation - Speed 17 Q1 Lantency-Approximate model Q2 Detailed queueing model

Model Evaluation - Loss Accuracy 18 Flow 1: 900 Mb/s Flow 2: 100 Mb/s, 200 Mb/s… 1Gb/s 10 million frames per flow Total Input Rate 3COM Switch

Conclusion and Future Work 19 Created a unique test-bed –Generate and capture gigabit Ethernet traffic at line rate with millions of frames –Measure precisely the latency and loss patterns in a switch Different switches has very distinct behavior and require different models Created simple model to reduce execution cost to 60%, almost one event per frame per switch; validated the models with real traffic To understand how switch behaves under realistic bursty traffic

Thanks! ? 20