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10/11/2014Anue Systems, Inc. 1 v1.0 - 20050426 Telecommunications Industry AssociationTR-30.3/08-12-016 Lake Buena Vista, FL December.

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Presentation on theme: "10/11/2014Anue Systems, Inc. 1 v1.0 - 20050426 Telecommunications Industry AssociationTR-30.3/08-12-016 Lake Buena Vista, FL December."— Presentation transcript:

1 10/11/2014Anue Systems, Inc. 1 v Telecommunications Industry AssociationTR-30.3/ Lake Buena Vista, FL December 8 - 9, 2008

2 10/11/2014Anue Systems, Inc. 2 Problem statement G.8261 currently describes a way (in Appendix VI) to test sync Interworking Functions by building a testbed. But -- it’s not repeatable.

3 10/11/2014Anue Systems, Inc. 3 Initial results match Input profileMeasured result

4 10/11/2014Anue Systems, Inc. 4 A test bed Measure delay under G.8261 Appendix VI test conditions…..

5 10/11/2014Anue Systems, Inc. 5 Model-based impairment profiles Build a bottom-up model of each network element Construct test scenarios by connecting together various model elements and run a simulation  Validate end-to-end results Still has shortcomings  As network changes, model params must also change  New technologies may require new model elements  Harder to make a general model than to measure one sample

6 10/11/2014Anue Systems, Inc. 6 Why create a software model? Creating a model and validating it against real networks provides valuable insight to guide further work  Which device parameters are most important  What metrics work best  What’s the best way to test (interop/conformance)  Understand tradeoffs in system deployment

7 10/11/2014Anue Systems, Inc. 7 Discrete event simulation of test bed.. One way to model is to use a discrete event simulator Develop models for the switches and dummy traffic generators. Anue is developing one such model for MEF18 testing. This is just the beginning of modeling  Further refinements are possible

8 10/11/2014Anue Systems, Inc. 8 Switch model Three main blocks in the switch model  Ingress, Queuing, Egress Ingress block:  Each input port has one. Makes forwarding decisions (L2/L3)  There’s no contention here.  Introduces delay (store/forward or cut-through) Queuing block:  One or more queues per output port. Holds packets till sent out.  Contention can happen here. Queue has limited size (shared)  Queue memory allocated in N-byte chunks.  May implement congestion avoidance (e.g. WRED)  Introduces queuing delay and packet loss. Egress:  Each output port has one. Services queues at the port’s bit rate.  If multiple output queues, contention can also happen here (e.g. Strict Priority, WRR, WFQ)

9 10/11/2014Anue Systems, Inc. 9 Model assumptions Initial focus is queuing delays  In the forward direction only All switches are non-PTP capable (asynch) No priority or congestion avoidance Wire delay is constant Assume each switch has at least one flip- flop domain transfer Ignore oscillator noise

10 10/11/2014Anue Systems, Inc. 10 Model parameters Ten switches (based on G.8261) Dummy load is Traffic Model 2 Queue size is 64k bytes  Allocated and deallocated in 64 byte chunks All links are gigabit Measure delay 1000 times per second Model outputs  Packet delay  Packet drop

11 10/11/2014Anue Systems, Inc. 11 But can’t realistically simulate all packets A 24-hour simulation of a 10 hop network built out of GE switches and operating at 50% load with 1400 byte (avg) packets represents about 40 Billion packets. That’s half a petabit. If you watched HDTV for two years straight, without sleeping, it would use about that many bits.

12 10/11/2014Anue Systems, Inc. 12 Example model results (20% load TM2) Reference (test bed) S/W Model Results

13 10/11/2014Anue Systems, Inc. 13 Simulation Results MEF18, 6.2a Based on G.8261 Appendix VI Test Case 3

14 10/11/2014Anue Systems, Inc. 14 Simulation Results MEF18, 6.6a Based on G.8261 Appendix VI Test Case 5 (congest 100s)

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