1 / 14

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.

amos-bishop
Download Presentation

v1.0 - 20050426

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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

More Related