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Locating Available Bandwidth Bottlenecks

This research presents techniques to identify tight links—bottlenecks in network bandwidth—using available bandwidth probing. By employing the STAB tool, which utilizes chirp-probe trains and self-induced congestion, we efficiently estimate bandwidth across multi-hop paths. Our findings include simulations validating the method and practical internet experiments. The technique promises applications in network monitoring and optimizing server selection by determining where tight links occur in both space and time.

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Locating Available Bandwidth Bottlenecks

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  1. Locating AvailableBandwidth Bottlenecks Vinay J. Ribeiro, Rudolf H. Riedi, and Richard G. Baraniuk Rice University By: 林佩君 s927468

  2. Outline • Introduction • Probing for Available Bandwidth • STAB Tool • Thin-Link Localization • Validation through Simulations • Internet Experiments • Conclusions

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

  4. Introduction(2) Key Definitions Path available bandwidth Sub-path available bandwidth Thin link (Tight link): link with least available bandwidth • Goal: use end-to-end probing to locate tight link in space and over time

  5. Introduction(3)Applications • Science: where do Internet tight links occur and why? • Network aware applications • - server selection • Network monitoring • - locating hot spots

  6. Probing for Available Bandwidth • Using self-induced congestion principle • The path’s queues won’t congest, if the probing bit rate is less than the available bandwidth.

  7. 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

  8. STAB Tool STAB’s three key ingredients • chirp-probe trains • feature exponential flight patterns of packets • self-induced congestion • an available bandwidth estimation technique that temporarily congests the network by increasing the probing bit rate • packet tailgating • a probing concept that allows estimation of spatially local network properties.

  9. chirp-probe trains • Chirps: exponentially spaced packets • Wide range of probing rates • Efficient:few packets

  10. Tight Link Localization 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

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

  12. 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

  13. Validation through Simulations

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

  15. Conclusions • STAB like hospital CAT scan • Network tomography transfers probe packets between multiple sender and receiver hosts to determine various internal properties of the network. • STAB using in wireless networks has some problem • poor channel quality and interference from neighboring wireless computers

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