Peer Assisted CDN

8/17/2019 Peer Assisted CDN

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Peer-Assisted ContentPeer-Assisted Content

Distribution Networks:Distribution Networks: Techniques and Challenges Techniques and ChallengesPei CaoPei Cao

Stanford UniversitStanford Universit


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Traditional !ntra-Provider Traditional !ntra-Provider

Content Distribution NetworksContent Distribution Networks

National Center

Regional Center

Branch

. . .

. . . . . .

Users. . . . . .. . . . . .


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Peer-to-Peer ContentPeer-to-Peer Content

DistributionDistribution

National Center

Regional Center

Branch

. . .

. . . . . .

Users. . . . . .. . . . . .


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P"P vs CDNP"P vs CDN

# P"P:P"P:$ No infrastructure costNo infrastructure cost

$ Su%%l grows linearl with de&andSu%%l grows linearl with de&and

$ Si&%le distributed' rando&i(ed algorith&sSi&%le distributed' rando&i(ed algorith&s

$ No )oSNo )oS

# CDN:CDN:

$ !nitial infrastructure cost!nitial infrastructure cost$ Centrali(ed scheduling algorith&sCentrali(ed scheduling algorith&s

$ Network e*ciencNetwork e*cienc

$ Ca%able of su%%orting )oSCa%able of su%%orting )oS


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Co&bine P"P with CDN+Co&bine P"P with CDN+

# Use P"P to co&%le&ent CDNUse P"P to co&%le&ent CDN$ P"P reduces load on the CDN' covers areasP"P reduces load on the CDN' covers areas

where CDN is not installedwhere CDN is not installed

$ ,ust be able to control' or sha%e.' P"P tra*c,ust be able to control' or sha%e.' P"P tra*c# Use CDN to co&%le&ent P"PUse CDN to co&%le&ent P"P

$ CDN ste%s in when %eer-based distribution isCDN ste%s in when %eer-based distribution is

falling short' enabling )oSfalling short' enabling )oS

$ ,ust be able to detect when %eers won/t &eet,ust be able to detect when %eers won/t &eetthe deliver ti&e guaranteethe deliver ti&e guarantee


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0utline0utline

# 1eview of 2itTorrent1eview of 2itTorrent

# Tra*c-sha%ing 2itTorrent: biased Tra*c-sha%ing 2itTorrent: biasedneighbor selectionneighbor selection

# )oS in 2itTorrent: deliver ti&e)oS in 2itTorrent: deliver ti&e%rediction%rediction


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2itTorrent 3ile Sharing2itTorrent 3ile Sharing

NetworkNetwork4oal: re%licate 5 chunks of data a&ong4oal: re%licate 5 chunks of data a&ong

N nodesN nodes

# 3or& neighbor connection gra%h3or& neighbor connection gra%h

# Neighbors e6change dataNeighbors e6change data


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2itTorrent: Neighbor2itTorrent: Neighbor

SelectionSelection Tracker7le8torrent9Seed

hole 7le

A

;

"<

=


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2itTorrent: Piece 1e%lication2itTorrent: Piece 1e%lication

Tracker7le8torrent9Seed

hole 7le

A

;

<


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2itTorrent: Piece 1e%lication2itTorrent: Piece 1e%lication

Algorith&sAlgorith&s

# Tit-for-tat. >choking?unchoking@: Tit-for-tat. >choking?unchoking@:$ ach %eer onl u%loads to B other %eers at a ti&each %eer onl u%loads to B other %eers at a ti&e

$ of these are chosen based on a&ount of data of these are chosen based on a&ount of data

received fro& the neighbor in the last " secondsreceived fro& the neighbor in the last " seconds

$ The last one is chosen rando&l' with a B;E bias The last one is chosen rando&l' with a B;E bias

toward newco&erstoward newco&ers

# >Focal@ 1arest-7rst re%lication:>Focal@ 1arest-7rst re%lication:$ hen %eer < unchokes %eer A' A selects whichhen %eer < unchokes %eer A' A selects which

%iece to download%iece to download


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Analsis of 2itTorrentAnalsis of 2itTorrent

# Conclusion fro& &odeling studies:Conclusion fro& &odeling studies:2itTorrent is nearl o%ti&al in2itTorrent is nearl o%ti&al in

ideali(ed' ho&ogeneous networksideali(ed' ho&ogeneous networks$ De&onstrated b si&ulation studiesDe&onstrated b si&ulation studies

$ Con7r&ed b theoretical &odeling studiesCon7r&ed b theoretical &odeling studies

# !ntuition: in a rando& gra%h'!ntuition: in a rando& gra%h'

Prob>Peer A/s content is a subset of Peer 2/s@ GProb>Peer A/s content is a subset of Peer 2/s@ G

;E;E


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Tra*c-Sha%ing 2itTorrent Tra*c-Sha%ing 2itTorrent


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1ando& Neighbor 4ra%h1ando& Neighbor 4ra%h

# 6isting studies all assu&e rando&6isting studies all assu&e rando&neighbor selectionneighbor selection

$ 2itTorrent no longer o%ti&al if nodes in2itTorrent no longer o%ti&al if nodes inthe sa&e !SP onl connect to each otherthe sa&e !SP onl connect to each other

# 1ando& neighbor selection1ando& neighbor selection highhigh

cross-!SP tra*ccross-!SP tra*c


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Di*cult in Tra*c-Sha%ing P"PDi*cult in Tra*c-Sha%ing P"P

A%%licationsA%%lications

# !SPs:!SPs:$ DiHerent links have diHerent &onetar costsDiHerent links have diHerent &onetar costs

$ Prefer clustering. of tra*cPrefer clustering. of tra*c# P"P A%%lications:P"P A%%lications:

$ No knowledge of underling !SP to%ologNo knowledge of underling !SP to%olog

$Use rando&i(ed algorith&s that don/t doUse rando&i(ed algorith&s that don/t dowell under clusteringwell under clustering

# Current solution: throttlingCurrent solution: throttling usersuserssuHersuHer


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A Network-3riendlA Network-3riendl

2itTorrent+2itTorrent+# !SPs infor& 2itTorrent of its link!SPs infor& 2itTorrent of its link

%references%references

# Algorith& of 2itTorrent is adIustedAlgorith& of 2itTorrent is adIustedsuch that both users and !SPs bene7tsuch that both users and !SPs bene7t

# 6a&%le: 2iased Neighbor Selection6a&%le: 2iased Neighbor Selection$ orks when cost function is transitiveorks when cost function is transitive


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2iased Neighbor Selection2iased Neighbor Selection

# !dea: of N neighbors' choose N-k fro&!dea: of N neighbors' choose N-k fro&%eers in the sa&e !SP' and choose k%eers in the sa&e !SP' and choose k

rando&l fro& %eers outside the !SPrando&l fro& %eers outside the !SP

!SP


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!&%le&enting 2iased Neighbor!&%le&enting 2iased Neighbor

SelectionSelection

# 2 Tracker2 Tracker$ Need !SP a*liations of %eersNeed !SP a*liations of %eers

#Peer to AS &a%sPeer to AS &a%s#Public !P address ranges fro& !SPsPublic !P address ranges fro& !SPs#S%ecial J-. KTTP headerS%ecial J-. KTTP header

# 2 tra*c sha%ing devices2 tra*c sha%ing devices$ !nterce%t %eer!nterce%t %eer tracker. &essagestracker. &essages

and &ani%ulate res%onsesand &ani%ulate res%onses

$ No need to change tracker or clientNo need to change tracker or client


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valuation ,ethodologvaluation ,ethodolog

# vent-driven si&ulatorvent-driven si&ulator$ Use actual client and tracker codes as &uch asUse actual client and tracker codes as &uch as

%ossible%ossible

$ Calculate bandwidth contention' assu&e %erfect fair-Calculate bandwidth contention' assu&e %erfect fair-

share fro& TCPshare fro& TCP

# Network settingsNetwork settings$ 9= !SPs' each with ; %eers' 95b?s u%load' 9,b?s9= !SPs' each with ; %eers' 95b?s u%load' 9,b?s

downloaddownload

$ Seed node' =5b?s u%loadSeed node' =5b?s u%load

$ 0%tional universit. nodes >9,b?s u%load@0%tional universit. nodes >9,b?s u%load@

$ 0%tional !SP bottleneck to other !SPs0%tional !SP bottleneck to other !SPs


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Fi&itation of ThrottlingFi&itation of Throttling


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Throttling: Cross-!SP Tra*c Throttling: Cross-!SP Tra*c

1edundanc: Average L of ti&es a data chunk enters the


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2iased Neighbor Selection:2iased Neighbor Selection:

Download Ti&esDownload Ti&es


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2iased Neighbor Selection:2iased Neighbor Selection:

Cross-!SP Tra*cCross-!SP Tra*c


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!&%ortance of 1arest-3irst!&%ortance of 1arest-3irst

1e%lication1e%lication

# 1ando& %iece re%lication %erfor&s1ando& %iece re%lication %erfor&sbadlbadl

$ !ncreases download ti&e b M=E - 9;E!ncreases download ti&e b M=E - 9;E$ !ncrease tra*c redundanc fro& < to 9=!ncrease tra*c redundanc fro& < to 9=

# 2iased neighbors 1arest-3irst2iased neighbors 1arest-3irst

,ore unifor& %rogress of %eers,ore unifor& %rogress of %eers


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Co&%arison with Si&%leCo&%arison with Si&%le

ClusteringClustering

# 4atewa %eer: onl one %eer4atewa %eer: onl one %eerconnects to the %eers outside theconnects to the %eers outside the

!SP' all other %eers onl connect to!SP' all other %eers onl connect to%eers inside the !SP%eers inside the !SP

$ 4atewa %eer &ust have high4atewa %eer &ust have high

bandwidthbandwidth

# !t is the seed. for this !SP!t is the seed. for this !SP

$ nds u% bene7ting %eers in other !SPsnds u% bene7ting %eers in other !SPs


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Co&bining 2iased NeighborCo&bining 2iased Neighbor

Selection with CachesSelection with Caches

# Under rando& neighbor selectionUnder rando& neighbor selection$ bandwidth require&ent of cache is highbandwidth require&ent of cache is high

# Under biased neighbor selectionUnder biased neighbor selection$ bandwidth needed fro& the cache isbandwidth needed fro& the cache is

reduced b an order of &agnitudereduced b an order of &agnitude


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ConclusionsConclusions

# 2 choosing neighbors well' 2itTorrent2 choosing neighbors well' 2itTorrentcan achieve high %eer %erfor&ancecan achieve high %eer %erfor&ance

without increasing !SP costwithout increasing !SP cost$ 2iased neighbor selection: choose initial2iased neighbor selection: choose initial

set of neighbors wellset of neighbors well

$Can be co&bined with throttling andCan be co&bined with throttling andcachingcaching

2itTorrent/s algorith& can be sha%edO2itTorrent/s algorith& can be sha%edO


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Deliver Ti&e PredictionDeliver Ti&e Prediction


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,otivation,otivation

# Provide deliver ti&e guarantee underProvide deliver ti&e guarantee underP"PCDNP"PCDN

# hat contributes to deliver ti&e of ahat contributes to deliver ti&e of adownload via 2itTorrent+download via 2itTorrent+

$ 3ro& si&ulations: seed bandwidth and3ro& si&ulations: seed bandwidth and

even re%lication of blockseven re%lication of blocks$ ,issing: node Ioin?leave dna&ics' TCP,issing: node Ioin?leave dna&ics' TCP

eHects' etc8eHects' etc8


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Side-b-Side FiveSide-b-Side Five

6%eri&ents6%eri&ents# Two clients' running on the sa&e Two clients' running on the sa&e

&achine' starting at the sa&e ti&e'&achine' starting at the sa&e ti&e'

downloading the sa&edownloading the sa&e# 9< e6%eri&ents fro& A%r-,a "9< e6%eri&ents fro& A%r-,a "

# 3ile si(es: B,2 98=423ile si(es: B,2 98=42

# Network si(e: 99 "9 %eersNetwork si(e: 99 "9 %eers# Duration: 9 hrs " dasDuration: 9 hrs " das


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1esults fro& 6%eri&ents1esults fro& 6%eri&ents

# Hective download rate: 9


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Sus%icion L9: SlowerSus%icion L9: Slower

Neighbors+Neighbors+

# Calculate unweighted average of observedCalculate unweighted average of observedthrough%ut at a%%lication levelthrough%ut at a%%lication level$ 1199: average fro& all neighbors: average fro& all neighbors

$ 11"": average fro& neighbors u%loading Q";52 of data: average fro& neighbors u%loading Q";52 of data$ 11


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Sus%icion L": 3ewer NeighborsSus%icion L": 3ewer Neighbors

U%loading to the Peer+U%loading to the Peer+

# Slot analsis: calculate download concurrencSlot analsis: calculate download concurrenc$ ,a6i&u& nu&ber of neighbors:


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Close. NeighborsClose. Neighbors

# RE of data downloaded fro& 9-=ERE of data downloaded fro& 9-=Eof neighborsof neighbors

# FetFet F(p)F(p) andand G(p)G(p) be the nu&ber ofbe the nu&ber ofneighbors that %rovidesneighbors that %rovides p p of data toof data to

%eers 3 and 4' then%eers 3 and 4' then

3>%@ Q 4>%@3>%@ Q 4>%@ %eer 3 is slower than 4%eer 3 is slower than 4$ This holds for % RE' B;E' and ;E This holds for % RE' B;E' and ;E


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hat &akes a neighborhat &akes a neighbor

close+close+# Not related to s%eed' or order ofNot related to s%eed' or order of

connection to %eer' or order ofconnection to %eer' or order of

unchoking b %eerunchoking b %eer


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Cost of De%arture of a CloseCost of De%arture of a Close

NeighborNeighbor

# De%arture cost: if one close neighborDe%arture cost: if one close neighborleaves' calculate the ti&e until theleaves' calculate the ti&e until the

earliest ne6t close neighborearliest ne6t close neighbor# The average de%arture cost:


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h Do Close Neighborsh Do Close Neighbors

FeaveFeave# 3ive %ossible reasons3ive %ossible reasons

$ A: 1ando& disconnectA: 1ando& disconnect

$ 2: 3inished downloading2: 3inished downloading$ C: Peer broke oH the relationshi%C: Peer broke oH the relationshi%

$ D: Neighbor broke oH the relationshi%D: Neighbor broke oH the relationshi%

# 1esults: 2 is &ost co&&on' followed1esults: 2 is &ost co&&on' followedb C?D' then Ab C?D' then A


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ConclusionsConclusions

# Content deliver ti&e in 2itTorrent isContent deliver ti&e in 2itTorrent isdeter&ined b:deter&ined b:

$ Neighbor u%load s%eedNeighbor u%load s%eed$ Stabilit of neighbor relationshi%Stabilit of neighbor relationshi%

#Disru%tion of the %airing leads to longDisru%tion of the %airing leads to longdeliver ti&edeliver ti&e

#Neighbors &a leave due to rando&Neighbors &a leave due to rando&disconnection' co&%letion of download' ordisconnection' co&%letion of download' or

7nding faster neighbors7nding faster neighbors


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Using CDN to Co&%le&entUsing CDN to Co&%le&ent

P"PP"P# Use nodes CDN as high-s%eedUse nodes CDN as high-s%eed

s%eciall &anaged seedss%eciall &anaged seeds

# Seeds are called to hel% whenever aSeeds are called to hel% whenever anode loses a close neighbornode loses a close neighbor


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Su&&arSu&&ar

# A wa to sha%e 2itTorrent tra*cA wa to sha%e 2itTorrent tra*c

# Predicting 2itTorrent %erfor&ance bPredicting 2itTorrent %erfor&ance b

&onitoring close %eer relationshi%&onitoring close %eer relationshi%


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1elated ork1elated ork

# ,an &odeling studies of 2itTorrent,an &odeling studies of 2itTorrent

# Si&ulation studiesSi&ulation studies

# ,easure&ents of real torrents,easure&ents of real torrents


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0ngoing ork0ngoing ork

# Five e6%eri&ents with biasedFive e6%eri&ents with biasedneighbor selectionsneighbor selections

# A k-regular gra%h algorith& withA k-regular gra%h algorith& withfaster convergencefaster convergence

# Protot%e i&%le&entation ofProtot%e i&%le&entation of

P"PCDN.P"PCDN.

Documents

Peer Assisted CDN