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End-to-end Methods for Traffic Shaping Detection, Performance Problem Diagnosis, Home Wireless Troubleshooting Partha Kanuparthy Joint work with Constantine Dovrolis AIMS 2011, CAIDA Friday, February 11, 2011 1 Three Tools ShaperProbe :


  1. End-to-end Methods for Traffic Shaping Detection, Performance Problem Diagnosis, Home Wireless Troubleshooting Partha Kanuparthy Joint work with Constantine Dovrolis AIMS 2011, CAIDA Friday, February 11, 2011 1

  2. Three Tools  ShaperProbe : End-to-end detection of traffic shaping GATech, M-Lab (under submission)   Pythia: Detection, localization, diagnosis of performance problems GATech, DoE (early work; 4 months)   Troubleshooting home wireless networks GATech, Intel Labs, CMU (early work; 6 months)  2 Friday, February 11, 2011 2

  3. ShaperProbe: End-to-End Detection of Traffic Shaping Friday, February 11, 2011 3

  4. In this part..  Detecting traffic shapers using active probing (ShaperProbe tool)  ISP case studies 4 Friday, February 11, 2011 4

  5. What is Traffic Shaping?  Practice of dropping link speeds after a burst period  smoothes traffic  helps in managing/reducing congestion  pricing service tiers using shared infrastructure  Why detect shaping?  SLA verification (customers)  configuration testing (operators) Upload: 7Mbps -> 2Mbps in 8s 5 Friday, February 11, 2011 5

  6. Traffic Shapers  Implemented using a Token Bucket at a link  accumulates tokens (bytes) at certain rate (bytes/s)  services packet when it has sufficient tokens Tokens Token  Cisco devices: rate-limit command Bucket  Shapers vs. Policers: Packets  shapers queue packets waiting for tokens; policers drop  we detect both Configuration: burst size, shaping rate 6 Friday, February 11, 2011 6

  7. ShaperProbe: Design Sender (S) sends a constant-rate stream at rate C to receiver (R)  R estimates received rate in small intervals  Probing stops when either:  R sees a level shift in timeseries, or  after 60s  Internet send rate = S R path capacity (C) 7 Friday, February 11, 2011 7

  8. Design: Capacity  Probing rate = path capacity C  We estimate path capacity C before probing:  S sends packet trains of N back-to-back packets  R estimates capacity by measuring dispersion of δ each train: C = ( N − 1) S packet size (1470B) ˆ δ Internet S R δ 8 Friday, February 11, 2011 8

  9. Design: Classification  The probing stream can be designed to emulate well-known applications:  change payload, etc.  e.g., Skype, BitTorrent, ...  some applications may be more likely to be shaped by ISP 9 Friday, February 11, 2011 9

  10. Detecting Shaping  Shaping is characterized by a level shift in received rate  we observe rate in intervals of 300ms  Level shift point if: Received rate ∆  all points before > all points after τ β  min. # points before and after Time Figure 1: Active probing: Level shift detection.  “large” drop in median rate (factor of 1.1): ˜ > γ ˜ R r ( i ) R r ( j ) i =1 ... τ j = τ ...n 10 Friday, February 11, 2011 10

  11. Shaping Configuration  We estimate shaping parameters in case of shaping:  shaping rate: median rate after level shift  burst size: based on bytes sent before level shift τ ρ ] ∆ ± [ R ( i ) − ˆ ρ ] ∆ � σ = ˆ [ R ( i ) − ˆ 2 burst size i =1 (bytes) Received rate ∆ τ shaping rate β (bps) Time Figure 1: Active probing: Level shift detection. 11 Friday, February 11, 2011 11

  12. The ShaperProbe Service  We run a service on M-Lab using 48 server replicas and a load balancer front end  servers connected to tier-1 ASes  Open source client: supported on 3 platforms  Currently 1500+ users a day 12 Friday, February 11, 2011 12

  13. ShaperProbe users say... 13 Friday, February 11, 2011 13

  14. ShaperProbe users say... 13 Friday, February 11, 2011 13

  15. Shaping in ISPs: some observations 14 Friday, February 11, 2011 14

  16. Overview of Data (till Sept. 2010)  M-Lab service has been up for a year (100k+ runs)  We look at a subset of 37,540 runs from 2,000+ ASes  Shaping detections in top-5 ASes in terms of runs: ISP Upstream (%) Dwnstrm. (%) 75.4 82.5 Comcast (3851/5105) (3506/4248) Road Runner 6.4 (69/1073) 63.3 (513/811) AT&T 13.4 (114/849) 17.7 (125/707) Cox 63.4 (399/629) 56.5 (252/446) MCI-Verizon 5.1 (25/490) 7.3 (31/426) 15 Friday, February 11, 2011 15

  17. Shaping factors  There isn’t a “yes-no” answer to “Is my ISP shaping traffic?”  Factors that affect shaping detections in an ISP:  tier of service  geographical region  link type: DSL? cable? Ethernet?  time-of-day  load conditions 16 Friday, February 11, 2011 16

  18. Case study: Comcast 16000 Capacity Capacity 60000 Shaping rate Shaping rate 14000 50000 12000 Rate (Kbps) Rate (Kbps) 40000 10000 8000 30000 6000 20000 4000 10000 2000 16000 0 30000 0 Burst size (KB) Burst size (KB) 14000 25000 12000 20000 10000 8000 15000 6000 10000 4000 5000 2000 0 0 0 500 1000 1500 2000 2500 3000 3500 0 500 1000 1500 2000 2500 3000 3500 Run ID Run ID (a) Upstream. (b) Downstream. C (Mbps) ρ (Mbps) σ (MB) Burst duration (s) C (Mbps) ρ (Mbps) σ (MB) Burst duration (s) 3.5 1 5 16.7 19.4 6.4 10 6.4 4.8 2 5, 10 15.2, 30.5 21.1 12.8 10 10.1 8.8 5.5 10 25.8 28.2 17 20 14.9 14.5 10 10 18.8 34.4 23.4 20 15.3 (a) Upstream. (b) Downstream. ] Comcast High Speed Internet FAQ: PowerBoost . [5] Comcast High-Speed Internet (residential; May 12 ] Comcast Business Class Internet (May 12, 2010) . 2010) . http://customer.comcast.com/Pages/ http://business.comcast.com/internet/ http://www.comcast.com/Corporate/Learn/ FAQListViewer.aspx?topic=Internet&folder= details.aspx . HighSpeedInternet/speedcomparison.html . 8b2fc392-4cde-4750-ba34-051cd5feacf0 . 17 Friday, February 11, 2011 17

  19. Case study: Comcast 16000 Capacity Capacity 60000 Shaping rate Shaping rate 14000 50000 12000 Rate (Kbps) Rate (Kbps) 40000 10000 8000 30000 6000 20000 4000 10000 2000 16000 0 30000 0 Burst size (KB) Burst size (KB) 14000 25000 12000 20000 10000 8000 15000 6000 10000 4000 5000 2000 0 0 0 500 1000 1500 2000 2500 3000 3500 0 500 1000 1500 2000 2500 3000 3500 Run ID Run ID (a) Upstream. (b) Downstream. C (Mbps) ρ (Mbps) σ (MB) Burst duration (s) C (Mbps) ρ (Mbps) σ (MB) Burst duration (s) 3.5 1 5 16.7 19.4 6.4 10 6.4 4.8 2 5, 10 15.2, 30.5 21.1 12.8 10 10.1 8.8 5.5 10 25.8 28.2 17 20 14.9 14.5 10 10 18.8 34.4 23.4 20 15.3 (a) Upstream. (b) Downstream. ] Comcast High Speed Internet FAQ: PowerBoost . [5] Comcast High-Speed Internet (residential; May 12 ] Comcast Business Class Internet (May 12, 2010) . 2010) . http://customer.comcast.com/Pages/ http://business.comcast.com/internet/ http://www.comcast.com/Corporate/Learn/ FAQListViewer.aspx?topic=Internet&folder= details.aspx . HighSpeedInternet/speedcomparison.html . 8b2fc392-4cde-4750-ba34-051cd5feacf0 . 17 Friday, February 11, 2011 17

  20. Case study: Comcast 16000 Capacity Capacity 60000 Shaping rate Shaping rate 14000 50000 12000 Rate (Kbps) Rate (Kbps) 40000 10000 8000 30000 6000 20000 4000 10000 2000 16000 0 30000 0 Burst size (KB) Burst size (KB) 14000 25000 12000 20000 10000 8000 15000 6000 10000 4000 5000 2000 0 0 0 500 1000 1500 2000 2500 3000 3500 0 500 1000 1500 2000 2500 3000 3500 Run ID Run ID (a) Upstream. (b) Downstream. C (Mbps) ρ (Mbps) σ (MB) Burst duration (s) C (Mbps) ρ (Mbps) σ (MB) Burst duration (s) 3.5 1 5 16.7 19.4 6.4 10 6.4 4.8 2 5, 10 15.2, 30.5 21.1 12.8 10 10.1 8.8 5.5 10 25.8 28.2 17 20 14.9 14.5 10 10 18.8 34.4 23.4 20 15.3 (a) Upstream. (b) Downstream. ] Comcast High Speed Internet FAQ: PowerBoost . [5] Comcast High-Speed Internet (residential; May 12 ] Comcast Business Class Internet (May 12, 2010) . 2010) . http://customer.comcast.com/Pages/ http://business.comcast.com/internet/ http://www.comcast.com/Corporate/Learn/ FAQListViewer.aspx?topic=Internet&folder= details.aspx . HighSpeedInternet/speedcomparison.html . 8b2fc392-4cde-4750-ba34-051cd5feacf0 . 17 Friday, February 11, 2011 17

  21. Case study: Comcast 16000 Capacity Capacity 60000 Shaping rate Shaping rate 14000 50000 12000 Rate (Kbps) Rate (Kbps) 40000 10000 8000 30000 6000 20000 4000 10000 2000 16000 0 30000 0 Burst size (KB) Burst size (KB) 14000 25000 12000 20000 10000 8000 15000 6000 10000 4000 5000 2000 0 0 0 500 1000 1500 2000 2500 3000 3500 0 500 1000 1500 2000 2500 3000 3500 Run ID Run ID (a) Upstream. (b) Downstream. C (Mbps) ρ (Mbps) σ (MB) Burst duration (s) C (Mbps) ρ (Mbps) σ (MB) Burst duration (s) 3.5 1 5 16.7 19.4 6.4 10 6.4 4.8 2 5, 10 15.2, 30.5 21.1 12.8 10 10.1 8.8 5.5 10 25.8 28.2 17 20 14.9 14.5 10 10 18.8 34.4 23.4 20 15.3 (a) Upstream. (b) Downstream. ] Comcast High Speed Internet FAQ: PowerBoost . [5] Comcast High-Speed Internet (residential; May 12 ] Comcast Business Class Internet (May 12, 2010) . 2010) . http://customer.comcast.com/Pages/ http://business.comcast.com/internet/ http://www.comcast.com/Corporate/Learn/ FAQListViewer.aspx?topic=Internet&folder= details.aspx . HighSpeedInternet/speedcomparison.html . 8b2fc392-4cde-4750-ba34-051cd5feacf0 . 17 Friday, February 11, 2011 17

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