Broadband Internet Performance:
A View from the Gateway
Srikanth Sundaresan, Walter de Donato,
Nick Feamster, Renata Teixeira,
Sam Crawford, Antonio Pescapè
Georgia Tech
University of Napoli
CNRS/UPMC Sorbonne Universités
SamKnows
What Affects Broadband
Performance?
• Important for regulators, consumers, ISPs
• Notion of performance is fuzzy
– What metrics should we measure?
– How to measure them?
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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Accurate Measurements are Difficult
Home Network: AT&T DSL
6 Mbps Down, 512 Kbps Up
Last Mile
ISP Network
speedtest.net: 4.4 Mbps, 140 Kbps
Netalyzr: 4.8 Mbps, 430 Kbps
End host measurements are not continuous,
and affected by confounding factors
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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The Case For the Gateway
Home Network: AT&T DSL
6 Mbps Down, 512 Kbps Up
Last Mile
ISP Network
speedtest.net: 4.4 Mbps, 140 Kbps
Netalyzr: 4.8 Mbps, 430 Kbps
Gateway: 5.6 Mbps, 460 Kbps
Gateway enables periodic measurements, and
can account for confounding factors
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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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
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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The Deployments
Last Mile
Internet
SamKnows/BISmark
Nearby Server
• 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
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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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
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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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
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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Interpreting Throughput Results
Different techniques measure different
aspects of throughput
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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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
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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Traffic Shaping: PowerBoost
• Cable companies advertise “PowerBoost”
– Short bursts of high bandwidth
• Non-existent in DSL
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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Traffic Shaping Varies Across Users
Short-term throughput significantly different
from sustainable throughput
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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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
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
13
Latency Measurements
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
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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Impact of Last-mile on Latency
Cable ISPs
DSL ISPs
DSL last-mile latencies can be very high
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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DSL Interleaving Affects Latency
Fastpath vs. Interleaved last-mile data path
9
8
7
6
5
4
3
2
1
Fastpath sends data in order, can recover from single losses
Fastpath is susceptible to bursty loss
9
6
3
8
5
2
7
4
1
Extra Delay
Interleaving sends data out-of-order, can recover from bursty loss
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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Throughput (Mbits/s)
Example: Latency-Throughput Tradeoff
2.5
2.2
User 2: high latency, low loss
User 1: low latency, high loss
30
10
Latency (ms)
Both users have
same service plan
Interleaving
decreases loss,
increases latency,
improves throughput
Interleaving creates a trade-off between
latency and throughput
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
17
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
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
18
Modem Buffers are Too Large
10 seconds!
Service plans can interact badly with
modem buffers
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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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
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
20
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
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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http://projectbismark.net
Broadband Internet Performance: A View from the Gateway
ACM SIGCOMM, Toronto., August 2011
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