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Locating Available Bandwidth Bottlenecks

Locating Available Bandwidth Bottlenecks. Vinay J. Ribeiro, Rudolf H. Riedi, and Richard G. Baraniuk Rice University By: 林佩君 s927468. Outline. Introduction Probing for Available Bandwidth STAB Tool Thin-Link Localization Validation through Simulations

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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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