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Towards Tunable Measurement Techniques for Available Bandwidth: 

Towards Tunable Measurement Techniques for Available Bandwidth Ningning Hu, Peter Steenkiste Carnegie Mellon University BEst 03 12 / 09 / 2003

Outline: 

Outline Our experience IGI andamp; PTR PaSt A taxonomy of current techniques Challenge – tunability

IGI & PTR: 

IGI andamp; PTR Uniform packet train probing techniques Measure either packet gap (IGI) or probing rate (PTR) Search for the turning point Turning Point – The smallest probing gap (largest probing rate) where it is not increased (decreased) by the background traffic Performance [JSAC Vol. 21, 03] Similar accuracy with Pathload Smaller overhead

Paced Start (PaSt): 

Paced Start (PaSt) Application of PTR Use PTR to improve TCP startup performance Similar in flavor to TCP NewReno PaSt uses multiple windows of data packet train to search for the turning point (available bandwidth) Performance [ICNP 03] Less packet loss Smaller startup time

What We Learned from PaSt: 

What We Learned from PaSt Application’s considerations are very important for the measurement technique design Accuracy IGI/PTR sometimes have 30% error, good enough? TCP startup: 50% error can be easily accommodated Overhead TCP startup: overhead is critical IGI/PTR took all effort to reduce the overhead Two-end control Hard to deploy TCP: an two end protocol Think MORE about applications!

Outline: 

Outline Our experience IGI andamp; PTR PaSt A taxonomy of current techniques Challenge – tunability

Taxonomy of Current Techniques: 

Taxonomy of Current Techniques Pathload IGI/PTR TOPP pathChirp Spruce Jacob Strauss, Dina Katabi, Frans Kaashoek Manish Jain, Constantios Dovrolis Bob Melander, Mats Bjorkman, Per Gunningberg Cprobe ABwE BFind …… Vinay J. Ribeiro, Rudolf H. Riedi, Richard G. Baraniuk, Jiri Navratil, Les Cottrell Ningning Hu, Peter Steenkiste

Taxonomy of Current Techniques: 

Taxonomy of Current Techniques The list of techniques here is not a complete list.

Outline: 

Outline Our experience IGI andamp; PTR PaSt A taxonomy of current techniques Challenge – tunability

The Challenges: 

The Challenges Two-end control Accuracy vs. overhead Extreme environment Deployment and Application – Tunability

Two-End Control: 

Two-End Control Single-end control needs echo packets Accurate timestamp for the echo packet is hard to get Extra delay on echo packet due to router R. Govindan and V. Paxon. Estimating router ICMP generation delays. PAM 02 K.G. Anagnostakis, et.al. cing: Measuring network-internal delays using only existing infrastruture. Infocom 03. Return path queueing Tunability #1: Single-end probing

Accuracy vs. Overhead: 

Accuracy vs. Overhead Accuracy is often a tradeoff with probing overhead Tunability #2: Enable application to configure the tradeoff between accuracy and probing overhead

Extreme Environment: 

Extreme Environment The environment where the bandwidth measurement assumptions don’t hold Time measurement assumption Available bandwidth determining factors Gigabit network [IMC 03, by Guojun Jin] Timing issues: Interrupt andamp; System call Wireless network Available bandwidth determining factor could be different Tunability #3: Deal with the environment of the future

Conclusion: 

Conclusion Our experience from IGI/PTR andamp; PaSt Active probing design must consider both accuracy and overhead The tradeoff is closely related with the application requirement Tunability is the key challenge for the deployment of current techniques for available bandwidth measurement Achieve single-end control Understand the tradeoff between accuracy and overhead Solve real system issues

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