Broadband Internet Performance: A View from the Gateway Srikanth Sundaresan, Walter de Donato, Nick Feamster, Renata Teixeira, Sam Crawford, Antonio Pescapè

Broadband Internet Performance: A View from the GatewaySrikanth Sundaresan, Walter de Donato,

Nick Feamster, Renata Teixeira, Sam Crawford, Antonio Pescapè

Georgia TechUniversity of Napoli

CNRS/UPMC Sorbonne UniversitésSamKnows

Broadband Internet Performance: A View from the Gateway ACM SIGCOMM, Toronto., August 2011

What Affects Broadband Performance?

• Important for regulators, consumers, ISPs• Notion of performance is fuzzy– What metrics should we measure?– How to measure them?

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Accurate Measurements are Difficult

End host measurements are not continuous, and affected by confounding factors

Home Network: AT&T DSL 6 Mbps Down, 512 Kbps Up

Last MileISP Network

speedtest.net: 4.4 Mbps, 140 Kbps

Netalyzr: 4.8 Mbps, 430 Kbps

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The Case For the Gateway

Gateway enables periodic measurements, and can account for confounding factors

Home Network: AT&T DSL 6 Mbps Down, 512 Kbps Up

Last MileISP Network

speedtest.net: 4.4 Mbps, 140 Kbps

Netalyzr: 4.8 Mbps, 430 KbpsGateway: 5.6 Mbps, 460 Kbps

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Contributions

• Study of access networks from the gateway• Insight into how to benchmark performance– Effect of measurement technique, traffic shaping– Effect of access link properties, home equipment

• Insight into broadband performance– Consistency of performance– Loss, jitter, time-of-day effects

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The Deployments

• Breadth: The FCC/SamKnows study– 4,000 gateways, 16 ISPs, multiple service plans

• Depth: The BISmark study– 16 gateways in Atlanta, on-demand measurements

• Duration: Dec 2010 – Jan 2011

SamKnows/BISmark

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Last MileInternet

Nearby Server


Results: Overview

• Throughput measurement technique depends on usage scenario

• Traffic shaping is highly variable across users• Access link characteristics affect performance• Modem buffers induce high latency

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Results: Overview



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Interpreting Throughput Results

Different techniques measure different aspects of throughput

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Results: Overview



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Traffic Shaping: PowerBoost

• Cable companies advertise “PowerBoost”– Short bursts of high bandwidth

• Non-existent in DSL

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Traffic Shaping Varies Across Users

Short-term throughput significantly different from sustainable throughput

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Results: Overview



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Latency Measurements

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Parameter What it captures

End-to-end Latency to nearby server

Last-mile Latency to edge of ISP network

Under Load Buffer delays due to cross traffic


DSL last-mile latencies can be very high

Impact of Last-mile on Latency

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Cable ISPs DSL ISPs


DSL Interleaving Affects Latency

9 8 7 6 5 4 3 2 1

Fastpath is susceptible to bursty loss

9 6 3 8 5 2 7 4 1

Fastpath sends data in order, can recover from single losses

Interleaving sends data out-of-order, can recover from bursty loss

Fastpath vs. Interleaved last-mile data path

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Extra Delay


Example: Latency-Throughput Tradeoff

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User 2: high latency, low loss

User 1: low latency, high loss

Thro

ughp

ut (M

bits

/s)

Latency (ms)10

2.5

2.2

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Both users have same service plan

Interleaving decreases loss, increases latency, improves throughput

Interleaving creates a trade-off between latency and throughput


Results: Overview



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Modem Buffers are Too Large

Service plans can interact badly with modem buffers

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10 seconds!


Conclusion

• The gateway provides unique insight into home network

• Throughput measurements are affected by measurement technique, shaping

• Latency is affected by last-mile, buffering• ISPs generally deliver consistent throughput,

with some time-of-day effects• How to mitigate buffering effects

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Future Work

• BISmark node deployment across the world– Currently nodes in US, South Africa

• Performance monitoring from the edge– Effect of peering on performance– IPv6 performance– Effect of CDN location, traffic engineering on

application performance• Measure the home network

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http://projectbismark.net

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Documents

Broadband Internet Performance: A View from the Gateway Srikanth Sundaresan, Walter de Donato, Nick Feamster, Renata Teixeira, Sam Crawford, Antonio Pescapè