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Experiments with Less than Best Effort (LBE) Quality of Service on GÉANT

This experiment explores the performance of LBE Quality of Service on GÉANT network, including packet reordering, packet loss, throughput, and one-way delay. Conclusions and recommendations are provided.

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Experiments with Less than Best Effort (LBE) Quality of Service on GÉANT

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  1. Experiments with Less than Best Effort (LBE) Quality of Service on GÉANT Tiziana Ferrari Experiment with LBE Quality of Service on GÉANT

  2. Experimental set-up (cont) Experiment with LBE Quality of Service on GÉANT

  3. Performance without congestion Experiment with LBE Quality of Service on GÉANT

  4. One-way delay Experiment with LBE Quality of Service on GÉANT

  5. IPDV • traffic volume: [10, 50] % • 2 flows (1 LBE, 1 BE) • maximum IPDV (BE): 11 usec • sample of 100 consecutive packets • IPDV negligible for both LBE and BE Experiment with LBE Quality of Service on GÉANT

  6. Packet reordering • - proportional to packet rate • affecting both LBE and BE • maximum IPDV (BE): 11 usec • sample of 100 consecutive packets • packet reordering due to the M-160 architecture Experiment with LBE Quality of Service on GÉANT

  7. Performance with congestion Experiment with LBE Quality of Service on GÉANT

  8. Packet loss • 3 LBE streams (75% of traffic load), 1 BE stream (25%), plus BE production • traffic • in case of LBE congestion: • no BE packet loss • no IP Premium packet loss (when IP Premium traffic is injected) • only LBE packet loss, proportional to the amount of LBE • traffic injected Experiment with LBE Quality of Service on GÉANT

  9. Throughput • 7 LBE streams, 2 BE streams, 1 IPP stream • load: [50, 100] % • in case of LBE congestion (traffic load: 100% of a STM-16) : • BE and IPP per-flow throughput equals the UDP input rate • only LBE throughput affected by LBE congestion Experiment with LBE Quality of Service on GÉANT

  10. One-way delay • 100 streams, 98 streams DE2 -> IT, 2 streams DE2 -> DE1 (LBE and BE) • LBE: • increase in both average and max one-way delay in case of congestion • max delta (max – min): 1.865 msec • BE: • Slight increse of average and max one-way delay • Max delta (max – min): 0.537 msec Experiment with LBE Quality of Service on GÉANT

  11. One-way delay frequency distributions (LBE) • test duration: 10 sec • time divided in time intervals of 0.1 sec each -> 100 intervals • for each interval, min/avg/max one-way delay is recorded Experiment with LBE Quality of Service on GÉANT

  12. One-way delay frequency distributions (BE) Experiment with LBE Quality of Service on GÉANT

  13. IPDV (LBE) • 2 streams: 1 LBE stream, 1 BE stream (DE2 -> IT) • considerable increase in maximum LBE IPDV • no difference in IPDV frequency distributions with and without congestion • (100 consecutive packets) Experiment with LBE Quality of Service on GÉANT

  14. Packet reordering • BE queue priority = LBE queue priority = high • extremely high percentage of out-of-order packets in case of congestion • percentage is a function of the packet rate of a given stream • it affects both BE and LBE traffic • the configuration of different queue priorities solves the problem of throughput loss • of BE end-to-end TCP streams Experiment with LBE Quality of Service on GÉANT

  15. Conclusions • LBE DSCP transparency on GEANT is possible • Correct isolation of BE traffic from LBE congestion • Negligible impact on BE one-way delay and IPDV • Packet reordering can be greatly reduced so that end-to-end TCP throughput is preserved, by: • assigning a lower weight to the EF queue • Configuring different priorities to the LBE and BE queues • Packet reordering seems to affect TCP best-effort throughput if the parameters are wrong. Experiment with LBE Quality of Service on GÉANT

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