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VDCF Simulations

VDCF Simulations. Greg Chesson, greg@atheros.com Aman Singla, aman@atheros.com. Overview. Notation Load(a,b,c) means there are a highest-priority stations, b at the next priority, c at the next priority, etc. May be shown as L(a,b,c,d).

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VDCF Simulations

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  1. VDCF Simulations Greg Chesson, greg@atheros.com Aman Singla, aman@atheros.com G. Chesson, A. Singa - Atheros

  2. Overview • Notation • Load(a,b,c) means there area highest-priority stations, b at the next priority, c at the next priority, etc. May be shown as L(a,b,c,d). • CWmin(a,b,c) describes the assignment of CWmins to Traffic Categories where a is assigned to the highest priority, b at the next, etc. May be shown as W(a,b,c,d). • QIFS(a,b,c), or Q(a,b,c), captures the setting of the QIFS[i] values by TC. • Simulation Software • Public version of the Berkeley NS2 software suite • Contact authors for details • Results • Usually 3 graphs per simulation • BW - An instantaneous bandwidth slot for one or more flows • LAT – a per-frame latency plot over the lifetime of the run • Lat-dist – latency distribution (i.e P% of the packets had latency less than x) • Scenarios • Usually fixed topology, varying load • Stations are added or removed usually on 3-sec intervals G. Chesson, A. Singa - Atheros

  3. Scenarios • Basic differentiation demonstration and comparison with legacy DCF • Load(4,2,10) – phones, 2 videos, 10 background stations • Load(4,4,8) – constant demand from stations, uses same W/Q settings as scenario (2), demonstrates robust behavior of mechanism • Extreme differentiation: 8 active TCs G. Chesson, A. Singa - Atheros

  4. Scenario 1 • A simple scenario meant only to compare with DCF and to observe the effects of CWmin and QIFS controls. • Load(2,4): two high-priority stations and 4 low-priority stations, all stations with backlogged queues (always ready to transmit) using UDP datagrams. • Topology: an AP is sinking all traffic from the 6 stations. • Simulation Runs (3 plots for each run: bw, lat, lat-dist): • DCF only - for comparison • W(15,31) Q(0,0) - uses CWmin but not QIFS • W(15,15) Q(0,1) - uses QIFS but not CWmin G. Chesson, A. Singa - Atheros

  5. 1 a bw Per-flow Dropped packet counts for IFQ/MAC IFQ means dropped from software queue MAC means retry count exceeded G. Chesson, A. Singa - Atheros

  6. 1 a lat G. Chesson, A. Singa - Atheros

  7. 1 a lat-dist G. Chesson, A. Singa - Atheros

  8. 1 b bw G. Chesson, A. Singa - Atheros

  9. 1 b lat G. Chesson, A. Singa - Atheros

  10. 1 b lat-dist G. Chesson, A. Singa - Atheros

  11. 1 c bw G. Chesson, A. Singa - Atheros

  12. 1 c lat-dist G. Chesson, A. Singa - Atheros

  13. Scenario 2 • Load(4,2,10) • 4 phone-like CBR flows (100 Kbit/s with 120B frames) • Bidirectional flows: 2 Stations plus AP, 4 flows, each STA is source+sink • 2 video-like CBR flows: 1 at 3 Mbit/s, 1 at 8 Mbit/s • 10 background flows: 5 UDP and 5 TCP • All other flows sink to AP unless specified otherwise • New station added every 3 sec. • Stations removed in same order after peak load is reached • Runs • W(15,15,31) Q(0,2,7) • W(15,15,31) Q(0,0,7) • W(15,15,31) Q(0,2,7) - video flows sourced at AP G. Chesson, A. Singa - Atheros

  14. 2 a bw videos Remove loads background phones G. Chesson, A. Singa - Atheros

  15. 2 a lat statistics video phone G. Chesson, A. Singa - Atheros

  16. 2 a lat-dist G. Chesson, A. Singa - Atheros

  17. 2 a vdcf-background vs dcf-background G. Chesson, A. Singa - Atheros

  18. 2 b bw Background flows not shown G. Chesson, A. Singa - Atheros

  19. 2 b lat G. Chesson, A. Singa - Atheros

  20. 2 b lat-dist G. Chesson, A. Singa - Atheros

  21. 2 c bw video sourced at AP Background flows not shown G. Chesson, A. Singa - Atheros

  22. 2 c lat video sourced at AP Lower latency than 2 b lat. Fewer phone-video collisions than 2-b. G. Chesson, A. Singa - Atheros

  23. 2 c lat-dist video sourced at AP G. Chesson, A. Singa - Atheros

  24. Scenario 3 • Load(4,4,8) – differentiation test using same W/Q as scenario 2 • 4 high priority stations, 4 middle priority, 8 low priority • All stations sending with backlogged queues to AP • Stations are sequenced on at 3-sec intervals, high-priority stations first • Stations are sequenced off after peak load is attained • Demonstrates good differentiation without needing to adjust W/Q • Uses W(15,15,31) Q(0,2,7) - same as scenario 2 • Uses W(15,15,15) Q(0,1,2) - different recipe G. Chesson, A. Singa - Atheros

  25. 3 a bw G. Chesson, A. Singa - Atheros

  26. 3 b bw G. Chesson, A. Singa - Atheros

  27. 3 a lat G. Chesson, A. Singa - Atheros

  28. 3 b lat G. Chesson, A. Singa - Atheros

  29. 3 a lat-dist G. Chesson, A. Singa - Atheros

  30. 3 b lat-dist G. Chesson, A. Singa - Atheros

  31. Scenario 4 • 8 streams, 8 TCs • Backlogged queues G. Chesson, A. Singa - Atheros

  32. 4 bw G. Chesson, A. Singa - Atheros

  33. 4 lat G. Chesson, A. Singa - Atheros

  34. 4 lat-dist G. Chesson, A. Singa - Atheros

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