EmNet:
Satisfying The Individual User
Through Empathic Home Networks
J. Scott Miller, John R. Lange & Peter A. Dinda
Department of Electrical Engineering and Computer Science
Northwestern University
Prescience Lab
http://presciencelab.org
http://empathicsystems.org
Summary
• User satisfaction in home broadband
environments varies dramatically across users
– There is no canonical user
– Demonstrated with user study
• EmNet: use per-user feedback to schedule
external link
– User satisfaction increases by 20%
• First network scheduling policy to use per-user
satisfaction
Outline
• User satisfaction in home networks
– User study with controlled conditions
• EmNet: Design and implementation
– Targets home network routers
• Evaluation
– User study with controlled conditions
Per-User Variation
• Traditional optimizations focus on a canonical
user
– Abstract definition for the average user
• Real users have large variability
– Different performance demands to achieve
satisfaction
• Optimizing for a single user is non-optimal
– Leads to both over and under provisioning
User study
• Variance in typical home network users
– Measured satisfaction with network performance
– Emulated home network environment
• 20 study participants
– Taken from University population
• 3 web applications
– Wikipedia, Image labeler, streaming video
• 16 cross traffic scenarios
– Both upload and download
• Collected per scenario satisfaction ratings
– Satisfaction measured on 10 point scale
Study Testbed
Test Subject
Emulated
Broadband
Link
Web Proxy
Internet
Network Bridge
(Home Router)
Cross Traffic Client
Cross Traffic Server
Interface
• Measurements collected via web interface
– Overlaid onto web pages viewed by users
• Router injected code in every web page viewed
Study Results
(Streaming Video)
Large Per-User variation in satisfaction
Average satisfaction varies between cross traffic scenarios
Implications
• There is no canonical user
– Users have different performance
expectations
• Per-user satisfaction can be collected in
real-time
• Optimal network scheduling requires
knowledge of user satisfaction
EmNet
• Designed to be embedded in home network
routers
– Optimizes home networks based on user satisfaction
• Components
–
–
–
–
User Interface (Satisfaction sensor)
Proxy server and Interface injector
Policy Controller
Network Controller
Proxy Server and User Interface
• Injects JavaScript interface onto web pages
• Monitors and tracks network traffic
– Associates connections with user input signals
On screen slider
– FlowSets
Real time satisfaction
measurements
• Real time measurements of user satisfaction
Used as input to policy
group
of connections
controller
– Corresponding to a given
– Drives bandwidth allocation decisions
Policy Controller
• Optimizes bandwidth allocation between network flows
– Maximizes user satisfaction
– Minimizes over-provisioning
• Output
– percentage
of bandwidth
allocated
per
Static
BW
Dynamic
BWFlowSet
• Input
– User satisfaction measurements
– Connections associated with each measurement
User
1
User Back
2
Ground
User
1
• Prevents link monopolization
Back
Ground
User
2
Back
Ground
– Guaranteed minimum static
allocationBack Ground
User
– Allocates bandwidth between FlowSets and background traffic
– Cost function
0
1
2
3 4 5 6 7 8 9 10
Satisfaction Rating Value
Network Controller
• Manages network connection performance
– Assigns actual bandwidth FlowSets
• Weighted Fair Queuing approach
– Weights are set to ensure proportional
allocation under load
System Architecture
• Designed for home network routers
User drives queuing
decisions
Evaluation
• EmNet prototype implementation
– Installed in network testbed
• Network controller in network bridge
– FreeBSD and DummyNET
• Simplistic cost function
– Users effectively pay for data (~$10)
User Study
• Separate from initial variability study
– 18 participants from university population
• Same 3 applications
– Wikipedia, Image Labeler, Streaming Video
• Subset of initial cross traffic scenarios
– Most significantly affecting satisfaction
• User interface was injected onto every page
– Collected results with and without control active
Evaluation Testbed
Test Subject
Satisfaction
Measurements
Internet
Network
Controller
Web Proxy
Network Bridge
(Home Router)
Cross Traffic Client
Cross Traffic Server
Results
Image Labeler
Video Streaming
General Results
• EmNet increases user satisfaction with a
nominal increase in bandwidth usage
– 20% more satisfied than without network control
– 12% more satisfied than static WFQ
– 6% more bandwidth than static WFQ
• Experimental cost function ineffective
– Users rarely decreased the slider to lower incurred
cost
– Cost function had no real world value
• Additional information in Northwestern Technical Report
• Prescience Lab
– http://plab.cs.northwestern.edu
• Empathic Systems
– http://empathicsystems.org/
• John Lange
– http://www.artifex.org/~jarusl