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v1.0 - 20050426

Telecommunications Industry Association TR-30.3/08-12-016 Lake Buena Vista, FL December 8 - 9, 2008. v1.0 - 20050426. 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.

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v1.0 - 20050426

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  1. Telecommunications Industry Association TR-30.3/08-12-016 Lake Buena Vista, FL December 8 - 9, 2008 Anue Systems, Inc. www.anuesystems.com v1.0 - 20050426

  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. Anue Systems, Inc. www.anuesystems.com

  3. Initial results match Input profile Measured result Anue Systems, Inc. www.anuesystems.com

  4. A test bed • Measure delay under G.8261 Appendix VI test conditions….. Anue Systems, Inc. www.anuesystems.com

  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 Anue Systems, Inc. www.anuesystems.com

  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 Anue Systems, Inc. www.anuesystems.com

  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 Anue Systems, Inc. www.anuesystems.com

  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) Anue Systems, Inc. www.anuesystems.com

  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 Anue Systems, Inc. www.anuesystems.com

  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 Anue Systems, Inc. www.anuesystems.com

  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. Anue Systems, Inc. www.anuesystems.com

  12. Reference (test bed) S/W Model Results Example model results (20% load TM2) Anue Systems, Inc. www.anuesystems.com

  13. Simulation Results MEF18, 6.2a Based on G.8261 Appendix VI Test Case 3 Anue Systems, Inc. www.anuesystems.com

  14. Simulation Results MEF18, 6.6a Based on G.8261 Appendix VI Test Case 5 (congest 100s) Anue Systems, Inc. www.anuesystems.com

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