1. pathChirp Efficient Available Bandwidth Estimation Vinay Ribeiro Rice University Rolf Riedi Rich Baraniuk

2. Network 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. Available Bandwidth Unused capacity along path Available bandwidth: Goal: use end-to-end probing to estimate available bandwidth

4. Applications Network monitoring Server selection Route selection (e.g. BGP) SLA verification Congestion control

5. Principle of Self-Induced Congestion Advantages –No topology information required –Robust to multiple bottlenecks TCP-Vegas uses self-induced congestion principle Probing rate < available bw  no delay increase Probing rate > available bw  delay increases

6. Chirp Packet Trains Exponentially decrease packet spacing within packet train Wide range of probing rates Efficient: few packets

7. Queuing Delay Signatures Goal: exploit information in queuing delay signature

8. Internet Experiments 3 common hops between SLAC  Rice and Chicago  Rice paths Estimates fall in proportion to introduced Poisson traffic

9. Conclusions Chirp trains –Probe at multiple rates simultaneously –Efficient estimates pathChirp –Self-induced congestion –Excursion detection Experiments –Internet experiments promising –Outperforms existing tools More information: spin.rice.edu