Presentation on theme: "10/11/2014Anue Systems, Inc. www.anuesystems.com 1 v1.0 - 20050426 Telecommunications Industry AssociationTR-30.3/08-12-016 Lake Buena Vista, FL December."— Presentation transcript:
10/11/2014Anue Systems, Inc. 1 v Telecommunications Industry AssociationTR-30.3/ Lake Buena Vista, FL December 8 - 9, 2008
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.
10/11/2014Anue Systems, Inc. 3 Initial results match Input profileMeasured result
10/11/2014Anue Systems, Inc. 4 A test bed Measure delay under G.8261 Appendix VI test conditions…..
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
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
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
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)
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
10/11/2014Anue 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
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.
10/11/2014Anue Systems, Inc. 12 Example model results (20% load TM2) Reference (test bed) S/W Model Results
10/11/2014Anue Systems, Inc. 13 Simulation Results MEF18, 6.2a Based on G.8261 Appendix VI Test Case 3
10/11/2014Anue Systems, Inc. 14 Simulation Results MEF18, 6.6a Based on G.8261 Appendix VI Test Case 5 (congest 100s)