ACompara)veStudyofAndroidandiOSforAccessingInternetStreamingServices

YaoLiu@GeorgeMasonUniversityFeiLi@GeorgeMasonUniversityLeiGuo@OhioStateUniversityBoShen@VuclipSongqingChen@GeorgeMasonUniversity

Internetstreamingtomobiledevices

•  Internetstreamingservicesreceiveanincreasingnumberofaccessfrommobiledevices– 25%ofYouTubeviewsarefrommobiledevices1

•  Today,50%ofmobilenetworktrafficisvideo2

•  By2016,thisnumberwillgrowto66%2

2�1.Datasource:YouTube2.Datasource:Cisco

PseudostreamingisusedinmobileInternetstreaming

GEThHp://*.youtube.com/videoplayback…

3

HTTP/1.1200OKContent‐Type:video/mp4Content‐Length:37MB

HTTP/1.1206Par)alContentContent‐Type:video/mp4Content‐Range:bytes10MB‐37MB/37MB

GEThHp://*.youtube.com/videoplayback…Range:bytes10MB‐37MB

Server‐sideobservaTons(from)

•  Server‐sidelogduringFebruary2011•  26,713,708HTTPrequests•  15,725videoclips•  27.4TBvideotraffic

•  397,940uniquevideosessionsfromiOSdevices•  884,648uniquevideosessionsfromAndroiddevices

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iOSandAndroidusedifferentcontentrequesTngapproaches

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iOS

HTTP200 HTTP206

%ofRequests 0.01 99.99

%ofTrafficAmount 0.001 99.999

Android

HTTP200 HTTP206

%ofRequests 27.30 72.70

%ofTrafficAmount 80.594 19.406

AlmostalliOStrafficisdeliveredusing

HTTPparTalcontentresponse(206)

80%ofAndroidtrafficisdeliveredusingstandardHTTPresponses(200)

MorerequestsaresentoutbyiOSdevices

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80%ofAndroidsessionsuseonlyonesingleHTTPrequest

50%iOSsessionsissuedmorethan12HTTPrequestspersession

MoretrafficisreceivedatiOSdevices

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28%iOSsessionsreceivedmoretrafficthanthefilesize

55%Androidsessionsdownloadedexactthe

sameamountoftrafficasthefilesize

Highlightsofserver‐sideobservaTons

•  iOSusesHTTPrangerequests,whileAndroidusesstandardHTTPrequests

•  Mul)pleHTTPrequestsareissuedwheniOSdevicesarewatchingstreamingvideo,while80%AndroidsessionsuseonlyoneHTTPrequest

•  28%iOSsessionsreceivedmoretrafficthanthevideofilesize,whileonly2%forAndroid

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Devicesusedforclient‐sideexperiments

Name OSversion MemorysizeiPodTouch iOS3.1.2 128MB

iPhone3G iOS4.2.1 128MB

iPhone3GS iOS5.0.1 256MB

iPhone4S iOS5.1 512MB

NexusOne Android2.3.4 512MB

KindleFire Android2.3.4 512MB

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Watchingan8‐minuteYouTubevideooniOSdevices(1)

•  8‐minutevideo,360P•  38,517,389bytes(36.7MBytes)

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#ofHTTPrequests

iPodTouch 261

iPhone3G 301

iPhone3GS 105

iPhone4S 67

MulTpleHTTPrequestswere

issuedtodownloadthestreamingdata

iOSdevicesfrequentlyabortHTTPconnecTons

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iPhone3GS

Onaverage,iPhone3GSuses61HTTPrequeststo

downloadthe8‐minutevideo

Availablememoryisfilledup,causingconnecTonstobeaborted

12

availablememory

currentplayback

AvailableMemory

currentplayback

resumedownloading

abortconnec)on

abortconnec)on

Watchingan8‐minuteYouTubevideooniOSdevices(2)

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iPodTouch

iPhone3G

iPhone3GS

iPhone4S

116% 65%

114%34%

Re‐downloadingcausesredundanttraffic

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iPhone3GS 0～16MBytesfinishdownloading

GEThHp://*.youtube.com/videoplayback…Range:bytes0‐16MB

[FIN,ACK](receivedfullvideocontent)

Watchingan8‐minuteYouTubevideooniOSdevices

•  8‐minutevideo,360P•  38,517,389bytes(36.7MBytes)

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#ofHTTPrequests

ReceivedHTTPbody(Bytes)

Re‐downloaded(Bytes)

iPodTouch 261 83,410,351 26,450,851

iPhone3G 301 82,616,828 37,449,911

iPhone3GS 105 63,713,281 11,523,915

iPhone4S 67 51,625,429 9,292,410

Limitedavailablememorycausesre‐downloading

missingin‐memorycontent

currentplayback

played

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Re‐downloadingamountisdifferentacrossdifferent

experimentswatchingthesamevideoonthesamedevice

Videofilesizevs.redundanttrafficamount

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Video1 Video2 Video3Dura%on(sec) 360 480 657

Filesize(Bytes) 29,503,221 38,517,389 53,405,910

LESSredundanttraffic

MOREredundanttraffic

iPodTouch

iPhone3G

iPhone3GS

iPhone4S

42,379,164 144%

42,322,498 143%

37,702,143 128%

32,248,384 109%

57,176,659 148%

74,442,375 193%

47,460,396 123%

44,538,836 116%

90,445,044 169%

86,933,886 163%

72,388,936 136%

61,731,408 116%

FindingswithiOS

•  Dynamicbuffermanagement– TheHTTPconnecTonisabortedwhentheplaybackbufferfillsup,causingmul)pleHTTPrangerequeststobeusedinonestreamingsession

– DownloadingresumeswhenmorememoryissuppliedbytheoperaTngsystem

– Usesre‐downloadingtofetchplayedcontentthathasbeenevictedfromthememory

– Causesredundanttraffic

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Watchingthesame8‐minuteYouTubevideoonAndroiddevices

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NexusOne KindleFire

#ofHTTPrequests

ReceivedHTTPbody(Bytes)

Re‐downloaded(Bytes)

NexusOne 1 38,517,389 0

KindleFire 1 38,517,389 0

AndroidusesTCPwindowtocontroldownloading

GEThHp://*.youtube.com/videoplayback…

20

HTTP/1.1200OKContent‐Type:video/mp4Content‐Length:37MB

[ACK]ACK=10MB,Window=0

...

[ACK]ACK=10MB,Window=64KB

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enum { kPageSize = 65535, kDefaultHighWaterThreshold = 20 * 1024 * 1024, kDefaultLowWaterThreshold = 4 * 1024 * 1024, kDefaultKeepAliveIntervals = 15000000, };

Codesnippetfrom:/libstagefright/include/NuCachedSource2.h

20MB4MB

StaTcbuffermanagementinAndroid

22

HighWaterThres

currentplayback

HighWaterThreshold

currentplayback

re‐openTCPwindow

closeTCPwindow

closeTCPwindow

LowWaterThreshold

FindingswithAndroid

•  Sta)cbuffermanagement– Keepsafixedamountofdatainthebuffer(HighWaterThresholde.g.,20MB)

– Downloadingisstrictlysynchronizedwiththeplaybackprogress(LowWaterThreshold)

– NoredundanttrafficistransmiHed

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Conclusion

•  Mobiledeviceshavealimitedamountofmemory

•  iOSusesadynamicbuffermanagementmethod– MulTpleHTTPrequests

– Redundanttraffic

•  Androidusesasta)cbuffermanagementmethod– OnesingleHTTPrequest– Noredundanttraffic

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