BROADBAND INTERNET PERFORMANCE: A VIEW FROM THE GATEWAY

Transcription

1 BROADBAND INTERNET PERFORMANCE: A VIEW FROM THE GATEWAY Sundaresan, de Donato, Feamster, Texeira, Crawford, and Pescapè SIGCOMM 11 Presented by Will Roever

2 BACKGROUND WHAT DOES IT MATTER? As of 2011, 500M residential broadband customers Fuzzy notion of broadband performance No measurement standards Widespread ISP-bashing Advertised speeds >> harsh reality Of interest to regulatory bodies responsible for evaluating providers, such as... YOUR ISP HERE 2

3 THE FCC 3

4 CONTRIBUTIONS & LESSONS LEARNED Value of the gateway approach to measurement is evident Measured throughput depends critically on the measurement techniques employed Traffic shaping makes cross-isp comparisons very difficult Hardware and configurations matter Modem buffer size contributes to latency DSL modem configuration can as well 4

5 REVIEW THE LAST MILE Many factors limit link throughput: Distance to DSLAM/CMTS Congestion Link noise DSL modem configs. fastpath vs. interleaving PowerBoost (Cable) 5

6 BROADBAND PERFORMANCE MEASUREMENT IS HARD To accurately measure and evaluate broadband performance, need to: Isolate the ISP access link Support continuous measurements (i.e. unlike Speedtest, Netalyzr) Allow for various home network configurations, hardware types 6

7 USE A GATEWAY! 7

8 FCC: MEASURING BROADBAND AMERICA In 2011, initiated Measuring Broadband America (MBA) program through SamKnows Participating households (4,200+) receive whiteboxes Raw data, applications are open-source Measure: Capacity (raw and bulk-transfer throughput) Latency (end-to-end, last-mile, under load) Jitter Loss Download times for 10 popular websites 8

9 MBA 2011: MEASURED THROUGHPUT 9

10 BISMARK Comprises gateway devices (Linux boxes), measurement servers, management server Deployed in 16 households in Atlanta, Dec Jan Measure: Capacity (raw and bulk-transfer throughput) Latency (end-to-end, last-mile, under load) Jitter Loss 10

11 THROUGHPUT MEASUREMENT METHODS YIELD INCONSISTENT RESULTS Reflects throughput as measured at 2 locations with both SamKnows and BISMark gateways Normalized throughput = measured / advertised Multi-threaded TCP and UCP more accurate, more robust to loss 11

12 DOWNLOAD AND UPLOAD THROUGHPUT ARE LARGELY CONSISTENT Reflects download throughput metrics for all SamKnows gateways Upload throughput exhibits more consistency 12

13 DOWNLOAD THROUGHPUT METRICS REVEAL CLEAR DIURNAL PATTERNS Throughput decreases and performance variability increases during peak hours for all ISPs Evidence of congestion? Or ISP throttling? 13

14 CABLE CUSTOMERS TEND TO EXPERIENCE BETTER LAST-MILE LATENCY THAN DSL SUBSCRIBERS DSL customers Last-mile latencies represent 10th percentile of first-hop traceroute times (excl. NATs) What can explain the longer latencies for DSL customers? Interleaving. 14

15 INTERLEAVING Sacrifices lower latency and jitter for robustness by interleaving link-layer segments (i.e. delivering out-of-order) Typically advantageous when: User is far from DSLAM User has a noisy link User is subscribes to multiple services that make use of the same access link 15

16 UPLOAD LATENCY IS UNIVERSALLY GREATER THAN DOWNLOAD LATENCY Consistent with research showing modem buffers are too large Authors observe substantial variation in upload latency in BISMark data depending on specific modem used 16

17 LIMITATIONS & FINAL THOUGHTS Knowledge of advertised rates (and modem details) would improve MBA dataset The BISMark dataset comes from a very small sample size - conclusions need validating Suggestions aren t especially useful from a policy or perspective Benchmarks? Traffic shaping -> gets at net-neutrality Some more work has been done here (e.g. Bischof et al.) 17

18 THANK YOU 18

19 APPENDIX ACTIVE MEASUREMENTS 19

20 APPENDIX LAST-MILE LATENCY & JITTER LATENCY JITTER 20

21 APPENDIX QUEUE-INDUCED LATENCY 21