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Transcript of MultiNets_ a System for Real-Time Switching Between Multiple Network Interfaces on Mobile Devices...
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8/10/2019 MultiNets_ a System for Real-Time Switching Between Multiple Network Interfaces on Mobile Devices Presentation
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MultiNets: A System for Real-Time Switching
between Multiple Network Interfaceson Mobile Devices
Angela NicoaraDeutsche Telekom Innovation Labs, Silicon Valley Innovation Center, US
Joint work with: Shahriar Nirjon, Cheng-Hsin Hsu,
Jatinder Pal Singh, John StankovicUniversity of Virginia, US
Department of Electrical Engineering, Stanford University, US
National Tsing Hua University, Taiwan
November 14, 2013
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Challenges in Todays Global Mobile Industry
*Source: Cisco VNI Mobile, 2012
*Source: Ciscos Global Mobile Data Traffic Forecast, 2012
788 million mobile-only Internet users by 2015
Global mobile traffic will increase by a factor of 26 by 2015
Mobile apps have increased the demand for more bandwidth
Meet todays functional demands and the explosive wireless marketgrowth that is expected over the next years
Slow battery energy density growth
Widening Energy GapChalamala, Proceedings of the IEEE, 2007
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Intelligently design system support to switch interfaces in real-time
to save energy, achieve higher throughput, offload data traffic
Heterogeneous Network Access
Devices leave the choice of selecting the network to the end-user
Real-time network switching system that allows each end-user to select ahigh-level goal, and automatically switches to the suitable network interface
Goals: 1) Save energy, 2) Higher throughput, 3) Offload data traffic
Phone usability is limited by battery life
Velocity Europe 2013 MultiNets: Heterogeneous Network Access for Mobile Devices | November 2013 by Dr. Angela Nicoara 3
Web Server
Back haul
Internet
WiFi AP
Base Station
IP3Phone
IP1
IP2
Heterogeneous Network Access
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WiFi 3G/2G
Activating a new interface and deactivating thecurrent interface:
Dynamically
Without interruptions Based on policy
The difficulty is:
Switching Interfaces
TCP is Connection-
Oriented
Switching Network Interfaces
Velocity Europe 2013 MultiNets: Heterogeneous Network Access for Mobile Devices | November 2013 by Dr. Angela Nicoara 4
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Backhaul
Web Server
Internet
WiFi Ps
Base Station ndroid
Mobile
Device
Our novel solution for migrating flows between different network interfaceswithout requiring changes to the existing applications, networking protocols, nor
backend servers, no extra support from the existing network infrastructure, nouser interventions, and with minimal impact to the user.
Migrating Network Flows
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Average lifetime of TCP sessions are ~2 sec.
Average concurrency of TCP sessions are < 2.
TCP activities are in bursts average ~3 sec.
TCP Characteristics
How many concurrent TCP sessions are thereat any instant of time within a mobile device?
What are the durations of these sessions?
How much activities are there over thesesessions?
Challenges / Questions
3-months long experiment to collect the usagedata from 13 Android phone users.
Users used a total of 221 apps, and 35 of theseapps require Internet connectivity.
Our study
Data activity of the longest TCP session for 100 sec
CDF of number of concurrent TCP sessions
TCP Characteristics in Android
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X Y
Step 1: Count #of TCP connections on X.
Step 2: Add routes for all existing
TCP connections on X.Step 3: Activate Y and start all new
sessions over Y.
Step 4: Deactivate X when there is no
session on X or timeout.
Switching Algorithm X => Y)
Switching between Network Interfaces
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ABCDbcd
ultiNets System Architecture
Kernel
Switching Core
State
Machine
MultiNet Switching API
Switching
Utility
(6) switching
action
Switching Engine(1) select
policy
Offloadtraffic
Selection Policy
(3) switching
needed?EnergySaving
Performance
Power
Monitoring Engine
Network
FlowWireless
(4) query
(7) change connectivity (5) read
(2)
getstate
Performs switchingdynamically
Based on 3 policies:
Energy Saving
Performance
Offload data traffic
Supports simultaneousmultiple network access
Design and principles aregeneral enough to beadopted in other mobile OSes
MultiNets System Architecture
ABCDbcd
mplementation
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ABCD
bcd
ultiNets System Layered Architecture
Layered architecture
Modular design that allows:
Extending the systemcapabilities without
requiring any changesto the architecture
Isolate the mechanism,policy and monitoringtasks
~860 lines of codeNo modification to kernel
Implementation
MultiNets System Layered Architecture
ConnectivityManager WiFiManager
NetworkInfo WiFiInfo
ConnectivityService WiFiService
MobileStateTracker WiFiStateTracker
WiFiNative
PublicAPI
Interna
lAPI
JNI
NativeCodes
Android MultiNets
NetworkUtils
android_net_wifi_WiFi.cpp android_net_Netutils.cpp
wifi.c ifc_utils.c
SwitchingManager
SwitchingInfo
switching_utils.cpp
swi_utils.c
SwitchingUtils
SelectionPolicy
SwitchingService
MonitoringService
Kernel
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Multiple Network Access
ABCDbcd
imultaneous Usage of Network Interfaces
API for using multiple networkinterfaces simultaneously forsending and receiving data toseparate remote devices.
Apps can request to use a
specific network interface forcommunicating with a specificremote device.
Example transferringsensitive data (e.g., usercredentials) over a secured
cellular network, and lesssensitive data over a publicWiFi network.
MultiNets API
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Switching time
duration between the instant whenthe engine decides to switch and the instant when itcompletely connects to the new interface anddisconnects the old one.
Example of switching: start sending data over 3G,switch to WiFi when the data rate over 3G exceeds16KBps, and switch back to 3G when the WiFi isidle for the last 30 sec.
Switching time illustration
Switching time overhead:
Switching to WiFi takes ~1sec more than switchingto 3G involving steps: scanning for access points,associating with one of them, handshaking and adhcp request that are not required for 3G
Switching Time and TCP Interruptions
Type Switching time
msec)
3G to WiFi
1212
WiFi to 3G 196
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Switching time in presence of data activity for different timeout valuesTimeout value of 30 sec or more makes the switching time ~15 sec,
and keeps the TCP disconnections < 1
Switching Time and TCP Interruptions
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Energy Measurement System
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Energy for Download & Upload Dataover 3G and WiFi
Average energy needed for downloading & uploading 4KB to 4MB over 3G and WiFi
Energy consumption during data activity is higher for 3G than WiFi
Upload data is more costly than download data
Upload energy increases with the amount of data being uploaded
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Energy for data transfers, turning and keeping on the network interfaces (3G & WiFi)
Screen brightness configured to minimumA data transfer request contains an energy setup cost of roughly 12 Joules for 3G
and 1 J for WiFi
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Who killed my battery? Measurements
Average idle power consumed by the WiFi network interface 295.85 mW
Average idle power consumed by the 3G network interface 3.11 mW
Turning on WiFi network interface 7.19 J
Turning on 3G network interface 13.13 J
3G setup cost before the first byte can be sent 12 J
WiFi setup cost before the first byte can be sent 1 J
Where the energy goes?
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Energy Savings Heuristic:
Remains in 3G during the idle time
Switches to WiFi during data activitySwitches back to 3G when WiFi is idle
Energy saving heuristic cuts down the average dailyenergy usage by 27.4% and is close to optimum.
Trace Driven Evaluation: Energy Saving
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Trace Driven Evaluation: Throughput
Performance Policy:Switches to the interface that has higher bandwidth
Uses signal strength to estimate bandwidth
Achievable throughput is 7 times higher with switching
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Trace Driven Evaluation: Offloading
Offload Policy: Switch to WiFi if available to connectCompute the average daily WiFi usage and compare it to the
amount of data that is possible to offload if MultiNets was used
With switching we are able to offload on average 79.82% of the
average daily usage
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Running MultiNets every 5 sec, we keep the overhead below 5%
System Overhead
Benchmark Description
Linpack Solves dense NxN system of linear equations.
Fps2d Measures 2D graphics frames per second.
CMark CaffeineMark embedded benchmark. Measures
performance of Java programs involving prime
generation, loop, logic, method, floats.
Graphics Draws opacity and transparent bitmaps.
Cpu CPU performance of MWIPS, MFLOPS, and
VAX MIPS (SP and DP).
Mem Memory copy operation.
File File create, write, read, and delete.
Lines of code Added Modified
C / C++ 209 0
Java 642 8
Lines of code
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Experiments:
3 Android phones: one into the energy efficiencymode, other 2 phones run Android one withWiFi enabled, and the other staying over 3G only.
Use a traffic generator to replay the same datatraffic in all the phones
37 WiFi APs, average signal strengths of -64.46dBm (inside) and -82.34 dBm (outside), and28 WiFi disconnections during the tour.
Energy saving mode saves about 33.75%
as compared to Android
The Stanford University campus tour
Real Deployment
MultiNets
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ConclusionPresented the problem of real-time switching between multiple
network interfaces on mobile devices
3-month long empirical study to understand the TCP characteristics
on Android mobile devices
Client-based system for dynamically and seamlessly switching
between WiFi and cellular networks based on 3 policies:
1) energy efficiency, 2) higher throughput, 3) offload data traffic
Tools for measuring the precise energy consumption on mobile
devices
System outperforms state-of-the-art Android either by saving up to
33.75% energy, or achieving near-optimal offloading, or achievingnear-optimal throughput
Techniques and principles are applicable to any mobile OSs and
extensible to any number of interfaces
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Thank You!