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Tomography-based Overlay Network Monitoring and its Applications. Yan Chen. Joint work with David Bindel, Brian Chavez, Hanhee Song, and Randy H. Katz UC Berkeley. Overlay Network Operation Center. End hosts. topology. measurements. Problem Formulation.

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Tomography based overlay network monitoring and its applications

Tomography-based Overlay Network Monitoring and its Applications

Yan Chen

Joint work with David Bindel, Brian Chavez, Hanhee Song, and Randy H. Katz

UC Berkeley


Problem formulation

Overlay Network Operation Center Applications

End hosts

topology

measurements

Problem Formulation

Given n end hosts on an overlay network and O(n2) paths, how to select a minimal subset of paths to monitor so that the loss rates/latency of all other paths can be inferred.

  • Key idea: select a basis set of k paths that completely describe all O(n2) paths (k «O(n2))

    • Select and monitor k linearly independent paths to compute the loss rates of basis set

    • Infer the loss rates of all other paths


Intuition through topology virtualization
Intuition through Topology Virtualization Applications

  • Virtual links: minimal path segments whose loss rates uniquely identified

  • Can fully describe all paths

1’

1

2

1

k =1

1

k = 2

1’

2’

2

1

2

3

2’

1’

1

1

3’

2

2

4

3

3

k = 3

4’

Virtualization

Real links (solid) and overlay

paths (dotted) going through them

Virtual links

5


Efficiency and adaptation
Efficiency and Adaptation Applications

  • Internet has moderate hierarchical structure [TGJ+02]

  • For reasonably large n, (e.g., 100), k = O(nlogn)

  • Tolerant to topology measurement errors

  • Incremental topology change detection and update of monitoring paths

    • End host join/leave

    • Routing changes


Experiments on Planet Lab Applications

  • 51 hosts, each from different organizations

    • 51 × 50 = 2,550 paths

  • Simultaneous loss rate measurement

    • 300 trials

    • In each trial, send a 40-byte UDP pkt to every other host

  • Simultaneous topology measurement

    • Traceroute

  • Experiments: 6/24 – 6/27

    • 100 experiments in peak hours


Tomography-based Overlay Monitoring Results Applications

  • Loss rate distribution

  • Accuracy

    • On average k = 872 out of 2550

    • Absolute error |p – p’|:

      • Average 0.0027 for all paths, 0.0057 for lossy paths

    • Small relative error and good lossy path inference

  • Topology measurement error tolerance

    • On average 245 out of 2550 paths have no or incomplete routing information

    • No router aliases resolved


Performance improvement with overlay
Performance Improvement with Overlay Applications

  • With single-node relay

  • Loss rate improvement

    • Among 10,980 lossy paths:

    • 5,705 paths (52.0%) have loss rate reduced by 0.05 or more

    • 3,084 paths (28.1%) change from lossy to non-lossy

  • Throughput improvement

    • Estimated with

    • 60,320 paths (24%) with non-zero loss rate, throughput computable

    • Among them, 32,939 (54.6%) paths have throughput improved, 13,734 (22.8%) paths have throughput doubled or more

  • Implications: use overlay path to bypass congestion or failures


Adaptive Overlay Streaming Media Applications

Stanford

UC San Diego

UC Berkeley

X

Demo available

HP Labs

  • Implemented with Winamp client and SHOUTcast server

  • Congestion introduced with a Packet Shaper

  • Skip-free playback: server buffering and rewinding

  • Total adaptation time < 4 seconds


Pros and cons about planet lab
Pros and Cons About Planet Lab Applications

+ Easy batch processing via SSH

- No root privileges

  • Many measurement tools don’t work!

    - Limited tools

  • Only ping and traceroute

  • but people are adding more, like scriptroute

    - Linux-only platform

  • New applications (multiplayer games, live media) are mostly on Windows platform

    - Limited programming language choices

  • Only C/C++ and perl, no Java


Backup slides
Backup Slides Applications



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