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Spatio-Temporal Available Bandwidth Estimation

This paper presents a methodology for estimating spatio-temporal available bandwidth and locating tight links in network paths using end-to-end probing. The approach combines self-induced congestion techniques with packet tailgating to accurately identify periods of tight link conditions. By analyzing normal and explosive packet flows, the research demonstrates robust estimation of available bandwidth, even in the presence of multiple bottlenecks. The findings are significant for applications in network monitoring and optimization. Internet experiments validate the effectiveness of the proposed techniques.

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Spatio-Temporal Available Bandwidth Estimation

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  1. Spatio-Temporal Available Bandwidth Estimation Vinay Ribeiro Rolf Riedi, Richard Baraniuk Rice University

  2. Network Path Model Packet delay = constant term (propagation, service time) + variable term (queuing delay) • End-to-end paths • Multi-hop • No packet reordering • Router queues • FIFO • Constant service rate

  3. Key Definitions Path available bandwidth Sub-path available bandwidth Tight link: link with least available bandwidth • Goal: use end-to-end probing to locate tight link in space and over time

  4. Applications • Science: where do Internet tight links occur and why? • Network aware applications • - server selection • Network monitoring • - locating hot spots

  5. Methodology • Estimate A[1,m] • For m>tight link, A[1,m] remains constant

  6. Principle of Self-Induced Congestion • Probing rate = R, path available bandwidth = A R < A no delay increase R > A delay increases • Advantages • No topology information required • Robust to multiple bottlenecks

  7. Packet Tailgating • Large packets of size P (TTL=m)small packets of size p • Large packets exit at hop m • Small packets reach receiver with timing information • Previously employed in capacity estimation

  8. Estimating A[1,m] • Key: Probing rate decreases by p/(p+P) at link m • Assumption:r<A[m+1,N],no delay change after link m R < A[1,m] no delay increase R > A[1,m] delay increases

  9. Tight Link Localization • Tight link: link after which A[1,m] remains constant • Applicable to any self-induced congestion tool: pathload, pathChirp, IGI, netest etc.

  10. pathChirp • Chirps: exponentially spaced packets • Wide range of probing rates • Efficient:few packets

  11. ns-2 Simulation tight link • Heterogeneous sources • Tight link location changes over time • pathChirp tracks tight link location change accurately estimate

  12. Internet Experiment SLACRice tight link • Two paths:UIUC Rice and SLACRice • Paths share 4 common links • Same tight link estimate for both paths UIUCRice tight link

  13. Comparison with MRTG Data SLACRice UIUCRice • A[1,m] decreases as expected • Tight link location differs from MRTG data by 1 hop

  14. High Speed Probing • System I/O limits probing rate • On high speed networks:  cannot estimate A using self-induced congestion

  15. Receiver System I/O Limitation • Treat receiver I/O bus as an extra link • Use packet tailgating • If then we can estimate A[1,N-1]

  16. Sender System I/O Limitations • Combine sources to increase net probing rate • Issue: machine synchronization

  17. Conclusions • Towards spatio-temporal available bandwidth estimation • Combine self-induced congestion and packet tailgating • Tight link localization in space and over time • ns-2 and Internet experiments encouraging • Solutions to system I/O bandwidth limitations spin.rice.edu

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