A Measurement Study of Internet Bottlenecks

1
A Measurement Study of Internet Bottlenecks

• Ningning Hu (CMU)
• Joint work with
• Li Erran Li (Bell Lab)
• Zhuoqing Morley Mao (U. Mich)
• Peter Steenkiste (CMU)
• Jia Wang (ATT)

2
Motivation

• Recent research progress on active probing makes
  it possible to locate bandwidth bottlenecks
• How persistent are the Internet bottlenecks?
• Important for measurement frequency
• What relationship exists between bottleneck and
  packet loss and queuing delay?
• Useful for congestion identification
• Are bottlenecks shared by end users within the
  same prefix?
• Useful for path bandwidth inference
• What causes intra-AS bottlenecks?
• Important for traffic engineering

3
Pathneck

• Bottleneck
• Bottleneck Link the link with the smallest
  available bandwidth on a network path
• Bottleneck Router the downstream router of a
  bottleneck link
• Pathneck
• An active probing tool that can detect Internet
  bottleneck location effectively and efficiently
• For details, please refer to
• Locating Internet Bottlenecks Algorithms,
  Measurements, and Implications SIGCOMM04
• Source code www.cs.cmu.edu/hnn/pathneck
• Pathneck output used in this work
• Bottleneck link location
• Route

4
Data collection
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960 Internet Destinations
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cmu
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D
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• Probing
• Source a CMU host
• Destinations 960 diverse IP addresses
• 10 continuous probings for each destination (1.5
  minutes)
• Repeat for 38 days (for persistence study)
• Limitations
• Pathneck can not cover the last hop
• 960 ltlt of Internet paths

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Outline

• How persistent are the Internet bottlenecks?
• Route persistence
• Bottleneck persistence
• What relationship is between bottleneck and
  packet loss and queuing delay?
• Are bottlenecks shared by end users within the
  same prefix?
• What causes intra-AS bottlenecks?

6
Terminology
probing set (persistent)
Day 1
not persistent

• Consider both AS-level route and location-level
  route

7
Route Persistence
AS level
Location level

• Route change is very common and must be
  considered for bottleneck persistence analysis
• Consistent with the results from Zhang, et. al.
  IMW-01 on route persistence

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Bottleneck Persistence

• Persistence of a bottleneck router
• Bottleneck Persistence of a path
• Max(Persist(R)) for all bottleneck router R
• Two views
• End-to-end view ? per (src, dst) pair
• Includes the impact of route change
• Route-based view ? per route
• Removes the impact of route change

of persistent probing sets R is bottleneck
Persist(R)
of persistent probing sets R appears
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Bottleneck Persistence
3

• Bottleneck persistence in route-based view is
  higher than end-to-end view
• AS-level bottleneck persistence is very similar
  to that from location level
• 20 bottlenecks have perfect persistence in
  end-to-end view, and 30 for route-based view

10
Outline

• How persistent are the Internet bottlenecks?
• What relationship exists between bottleneck and
  packet loss and queuing delay?
• Are bottlenecks shared by end users within the
  same prefix?
• What causes intra-AS bottlenecks?

11
Motivation

• Possible congestion indication
• Large queuing delay
• Packet loss
• Bottleneck
• They do not always occur together
• Packet scheduling algorithm ? large queuing delay
• Traffic burstiness or RED ? packet loss
• Small link capacity ? bottleneck
• Bottleneck ??? link loss large link delay

12
Method

• Collected on the same set of 960 paths, but
  independent measurements
• Detect bottleneck location using Pathneck
• Detect loss location using Tulip
• Only use the forward path results
• Detect link queuing delay using Tulip
• medianRTT minRTT
• Tulip was developed in University of
  Washington, SOSP03
• Our analysis is based on the 382 paths for which
  both bottleneck location and packet loss are
  detected

13
Bottleneck ?? Packet Loss
14
Bottleneck ?? Link Delay
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More Results

• How persistent are the Internet bottlenecks?
• What relationship exists between bottleneck and
  packet loss and queuing delay?
• Are bottlenecks shared by end users within the
  same prefix?
• What causes intra-AS bottlenecks?

16
Related Work

• Persistence of Internet path properties
• Zhang IMW-01, Paxson TR-2000, Labovitz
  TON-1998, Infocom-1999
• Congestion points sharing
• Katabi TR-2001, Rubenstein Sigmetrics-2000
• Correlation among Internet path properties
• Paxson 1996
• Correlation between router and link properties
• Agarwal PAM 2004

17
Conclusion

• Only 20-30 Internet bottlenecks have perfect
  persistence
• Application should be ready for bottleneck
  location change
• Bottleneck locations have a fairly strong (60)
  correlation with packet loss locations
• Bottleneck and loss detections should be used
  together for congestion detection
• End users within common cluster share bottlenecks
  only with a low probabilityh
• End user can not assume common bottlenecks
• We observe evidence of a correlation between
  bottleneck and link loads
• Network engineers should focus on traffic load to
  eliminate bottlenecks