multinets_ a system for real-time switching between multiple network interfaces on mobile devices...

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

Velocity Europe 2013 MultiNets: Heterogeneous Network Access for Mobile Devices | November 14, 2013 1


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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

Velocity Europe 2013 MultiNets: Heterogeneous Network Access for Mobile Devices | November 2013 by Dr. Angela Nicoara 2


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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


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



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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


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!

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