VIA : Improving Internet Telephony Quality VIA Using Predictive - - PowerPoint PPT Presentation

VIA VIA: Improving Internet Telephony Quality

Using Predictive Relay Selection

Junchen Jiang, Rajdeep Das, Ganesh Ananthanarayanan, Philip A. Chou, Venkata N. Padmanabhan, Vyas Sekar, Esbjorn Dominique, Marcin Goliszewski, Dalibor Kukoleca, Renat Vafin, Hui Zhang

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Key takeaways in one minute

One fifth of calls use paths with poor network performance “Managed Overlay” could alleviate over half of calls on these paths VIA: Data-driven relaying can realize most Managed Overlay’s potential We studied 430 million Skype calls and found…

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20 40 60 80 2004200520062007200820092010201120122013 Million

Peak # of users concurrent online on Skype

Internet telephony is everywhere!

More apps focusing on Internet telephony

https://blogs.skype.com/2013/04/03/thanks-for-making-skype-a-part-of-your-daily-lives-2-billion-minutes-a-day/

Rapid growth over the last decade

https://www.statista.com/chart/1417/skype-usage/ 3

Call quality is sensitive to bad network performance

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0.2 0.4 0.6 0.8 1 200 400 600 Normalized Poor Call Rate RTT (ms) 0.2 0.4 0.6 0.8 1 1 2 3 4 Loss rate (%) 0.2 0.4 0.6 0.8 1 5 10 15 20 25 Jitter (ms)

Thresholds of poor network performance Datasets: Avg RTT, loss rate, jitter for each call of 430 million Skype calls Small fraction has user-provided quality scores 320ms 1.2% 12ms

Many calls have poor network performance

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17% 17% 12%

One fifth of calls have poor network performance Our goal: Alleviate poor network performance for Skype

Outline

• Problem: Network performance of Skype is bad

è Opportunity: Managed Overlay has huge potential

• Solution: VIA for optimal relay selection
• Evaluation: VIA is close-to-optimal

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Revisiting Overlay Networks by Managed Overlay

Managed Overlay has new benefits

• World-wide distributed DCs as relays
• Well connected
• Deployed by many providers
• Single administrative entity

How much can Internet telephony benefit from it?

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Selecting the best relay option

Key is to select the best relay option (direct, one-relay, or multi-relay) Q1: Does picking best relay option have significant impact? Q2: If so, how to pick the best relay option?

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Direct path One-relay hop Multi-relay hops

Managed Overlay has huge potential benefit

Substantial fraction of bad-performance calls could be alleviated

Consider an oracle that picks the best relay option for each src-dst AS pair in 24 hours

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10 20 30 40 50 60 RTT Loss Jitter At least one bad Poor performance: RTT > 320ms; Loss rate > 1.2%; Jitter > 12ms % calls “Bad” è “Good”

Outline

• Problem: Network performance of Skype is bad
• Opportunity: Managed Overlay has huge potential

è Solution: VIA for optimal relay selection

• Evaluation: VIA is close-to-optimal

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VIA: Realizing the benefit of Managed Overlay using Centralized Predictive Control

Quality of existing calls Relay selection VIA Control Algorithm

Predict the best relay option based

• n other calls’ performance

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Strawman 1: Pure prediction-based

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Use long-term history to predict performance

Relay options A new call

Problem: Call performance has great inherent variance

E.g., predicting “next day” using “last week” leads to over 30% error on latency. Call history Quality prediction

Strawman 2: Pure exploration-based

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In a short time window, explore relay options, then exploit the best one

Relay options Calls of one AS pair per day

Problem: Call distribution is highly skewed “# of actual calls >> # of relay options” NOT true for most AS pairs

Key idea: Guided exploration

Prediction-based Exploration-based

XOR Strawmen

VIA

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0.2 0.4 0.6 0.8 1 1 2 3 4 5 6 7 8 9 Probability of the best relay being in top k k Top k can be more easily predicted and can be more efficiently explored!

VIA’s idea: Guided Exploration

Rough prediction can still identify top k candidates, which can be explored efficiently. Predicting top 1 is too hard

Step 1: Prediction-based pruning

Latency

Confidence interval of quality prediction Top-k candidates Focus on relay options whose confidence intervals are better than those of others.

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Call history Upper bound of “blue” and “yellow” is better than the lower bound of “green” and “red”

Step 2: Exploring top-k candidates

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Multi-armed bandit process Upper Confidence Bounds (UCB1) Reward Our problem looks like MAB UCB1 with domain-specific twists Reward Reward How to maximize rewards? How to minimize latency? UCB1: Always pick the

• ne with the highest UCB

Putting them together: Gu

Guid ided Exp xplo loratio ion in in act ctio ion

Call history Performance measurements Tomography-based coverage expansion Predictive selection of top k candidates Modified UCB1 on the top k candidates To explore more relays Real-time relay selection Runs per call Prediction-based Pruning Updates every T hours Top-k candidates per AS pair

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All relay options

More in our paper

• Budgeted relaying
• Network tomography
• Granularity of prediction
• International vs. domestic calls

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Outline

• Problem: Network performance of Skype is bad
• Opportunity: Managed Overlay has huge potential
• Solution: VIA for optimal relay selection

è Evaluation: VIA is close-to-optimal

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VIA achieves close-to-optimal performance

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Poor performance: RTT > 320ms; Loss rate > 1.2%; Jitter > 12ms % calls “Bad” è “Good” 10 20 30 40 50 60 RTT Loss Jitter At least one bad Optimal VIA Prediction-based Exploration-based

Benefit varies across ASes

20 40 60 80 100 Source AS1 Source AS2 Source AS3 Oracle VIA Substantial improvement Limited room for improvement Room for further improvement

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% calls “Bad” è “Good”

Conclusion

• Internet telephony is here to stay
• Problem: One fifth of calls have bad network performance.
• Opportunity: Managed Overlay could significantly reduce bad-performance calls.
• Challenges: Optimal relay selection

Pure prediction and pure exploration won’t work!

• Solution: VIA can realize most of the benefit of Managed Overlay.

Key idea: Guided exploration: Predictive pruning of relay options + Exploration over top k candidates

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