ch.11 multimedia and qos

7/25/2019 Ch.11 Multimedia and QoS

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11: Multimedia Networking 11-1

Chapter 11

Multimedia Networking

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Computer Networking: A TopDown Approach

5thedition.Jim Kurose Keith !oss

Addison"#esle$ April %&&'.


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11: Multimedia Networking 11-.

Multimedia and (ualit$ o) *er+ice: #hat is it,

multimedia applications:network audio and +ideo-continuous media/0

network pro+idesapplication with le+el o)per)ormance needed )orapplication to )unction.

(o*


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Chapter : goals

2rinciples classi)$ multimedia applications identi)$ network ser+ices applications need making the 3est o) 3est e))ort ser+ice

2rotocols and Architectures speci)ic protocols )or 3est"e))ort mechanisms )or pro+iding (o*

architectures )or (o*


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11: Multimedia Networking 11-

Chapter outline

.1 multimedia networkingapplications

.%streaming stored audioand +ideo

.4making the 3est out o)3est e))ort ser+ice

. pro+iding multipleclasses o) ser+ice

.5pro+iding (o*guarantees


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MM Networking Applications

6undamentalcharacteristics: t$picall$ delaysensitive

end"to"end dela$

dela$ 7itter loss tolerant: in)re8uent

losses cause minorglitches

antithesis o) data whichare loss intolerant3utdela$ tolerant.

Classes o) MM applications:10 stored streaming

%0 li+e streaming

40 interacti+e real"time

Jitteris the +aria3ilit$o) packet dela$s withinthe same packet stream


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*treaming *tored Multimedia

*tored streaming: media stored at source transmitted to client streaming:client pla$out 3egins

3e)oreall data has arri+ed timing constraint )or still"to"3e transmitted

data: in time )or pla$out so collect 91& sec 3u))er 3e)ore pla$out starts


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*treaming *tored Multimedia:#hat is it,

1. +ideorecorded

%. +ideosent

4. +ideo recei+edpla$ed out at client

Cumu

lati+edata

streaming:at this time clientpla$ing out earl$ part o) +ideowhile ser+er still sending laterpart o) +ideo

networkdela$

time


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*treaming *toredMultimedia: nteracti+it$

;C!"like )unctionalit$:client canpause rewind 66 push slider 3ar 1& sec initial dela$


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*treaming =i+eMultimedia

>?amples: nternet radio talk show li+e sporting e+ent

*treaming -as with streaming storedmultimedia0 pla$3ack 3u))er pla$3ack can lag tens o) seconds a)ter

transmission timing constraint

nteracti+it$ )ast )orward impossi3le rewind pause possi3le@


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11: Multimedia Networking 11-1/

!eal"Time nteracti+e Multimedia

end"end dela$ re8uirements: audio: 15& msec good && msec


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Multimedia


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11: Multimedia Networking 11-1.

Iow should the nternet e+ol+e to 3ettersupport multimedia,

ntegrated ser+ices philosoph$: )undamental changes in

nternet so that apps canreser+e end"to"end3andwidth

re8uires new comple?so)tware in hosts routers

=aisse")aire no ma7or changes more 3andwidth when

needed content distri3ution

application"la$er multicast application la$er

Di))erentiated ser+icesphilosoph$: )ewer changes to nternet

in)rastructure $et pro+ide1st and %nd class ser+ice

#hatEs $our opinion,


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Chapter outline


.% streaming stored audioand +ideo





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*treaming *tored Multimedia

application"le+el streamingtechni8ues )or making the3est out o) 3est e))ortser+ice:

client"side 3u))ering use o) GD2 +ersus TC2 multiple encodings o)

multimedia

7itter remo+al

decompression error concealment graphical user inter)ace

wF controls )orinteracti+it$

Media 2la$er


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constant 3itrate +ideo

transmission

Cumu

lati+edata

time

+aria3le

networkdela$

client +ideoreception

constant 3itrate +ideo

pla$out at client

client pla$out

dela$

3u))ere

d

+ideo

*treaming Multimedia: Client Hu))ering

client"side 3u))ering pla$out dela$ compensate)or network"added dela$ dela$ 7itter


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*treaming Multimedia: GD2 or TC2,GD2 ser+er sends at rate appropriate )or client -o3li+ious to network congestion @0

o)ten send rate encoding rate constant rate then )ill rate constant rate " packet loss

short pla$out dela$ -%"5 seconds0 to remo+e network 7itter error reco+er: time permitting

TC2 send at ma?imum possi3le rate under TC2 )ill rate )luctuates due to TC2 congestion control larger pla$out dela$: smooth TC2 deli+er$ rate ITT2FTC2 passes more easil$ through )irewalls


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Gser Control o) *treaming Media: !T*2

ITT2 does not target

multimedia content no commands )or )ast

)orward etc.!T*2: !6C %4%L client"ser+er application

la$er protocol

user control: rewind)ast )orward pauseresume repositioningetc

#hat it doesnEt do: doesnEt de)ine how

audioF+ideo isencapsulated )or

streaming o+er network doesnEt restrict how

streamed media istransported -GD2 or

TC2 possi3le0 doesnEt speci)$ how

media pla$er 3u))ersaudioF+ideo


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Chapter outline



.4 making the 3est out o)3est e))ort ser+ice




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nternet 2hone: 2acket =oss and Dela$

network loss:2 datagram lost due to networkcongestion -router 3u))er o+er)low0 dela$ loss:2 datagram arri+es too late )or

pla$out at recei+er

dela$s: processing 8ueueing in network end"s$stem -sender recei+er0 dela$s t$pical ma?imum tolera3le dela$: && ms

loss tolerance: depending on +oice encoding losses

concealed packet loss rates 3etween 1O and 1&Ocan 3e tolerated.


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11: Multimedia Networking 11-./

nternet 2hone: 6i?ed 2la$out Dela$

recei+er attempts to pla$out each chunk e?actl$ 8msecs a)ter chunk was generated. chunk has time stamp t: pla$ out chunk at tP8 . chunk arri+es a)ter tP8: data arri+es too late

)or pla$out data lost/ tradeo)) in choosing 8:

large 8:less packet loss small 8:3etter interacti+e e?perience


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11: Multimedia Networking 11-.1

6i?ed 2la$out Dela$

p a c k e t s

t i m e

p a c k e t s

g e n e r a t e d

p a c k e t s

r e c e i v e d

l o s s

rp p 5

p l a y o u t s c h e d u l e

p ' - r

p l a y o u t s c h e d u l e

p - r

sender generates packets e+er$ %& msec during talk spurt.

B)irst packet recei+ed at time rB)irst pla$out schedule: 3egins at pBsecond pla$out schedule: 3egins at pE


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11: Multimedia Networking 11-..

Adapti+e 2la$out Dela$ -10

packetithreceivingafterdelaynetworkaverageofestimated

acketpithfordelaynetworktr

receiveratplayedisipackettimethep

receiverbyreceivedisipackettimether

packetiththeoftimestampt

i

ii

i

i

i

=

=

=

=

=

d$namic estimate o) a+erage dela$ at recei+er:

)()1( 1 iiii trudud +=

where uis a )i?ed constant -e.g. u .&10.

Qoal:minimie pla$out dela$ keeping late loss rate low

Approach:adapti+e pla$out dela$ ad7ustment: estimate network dela$ ad7ust pla$out dela$ at 3eginning o)

each talk spurt. silent periods compressed and elongated. chunks still pla$ed out e+er$ %& msec during talk spurt.


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Adapti+e pla$out dela$ -%0

also use)ul to estimate a+erage de+iation o) dela$ +i:

||)1(1 iiiii dtruvuv +=

estimates di +icalculated )or e+er$ recei+ed packet-3ut used onl$ at start o) talk spurt

)or )irst packet in talk spurt pla$out time is:

iiii Kvdtp ++=

where K is positi+e constant

remaining packets in talkspurt are pla$ed out periodicall$


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Adapti+e 2la$out -40

(:Iow does recei+er determine whether packet is)irst in a talkspurt, i) no loss recei+er looks at successi+e timestamps.

di))erence o) successi+e stamps R %& msec ""Rtalk spurt

3egins. with loss possi3le recei+er must look at 3oth time

stamps and se8uence num3ers. di))erence o) successi+e stamps R %& msec andse8uence

num3ers without gaps ""R talk spurt 3egins.


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!eco+er$ )rom packet loss -10

6orward >rror Correction

-6>C0: simple scheme )or e+er$ group o) n chunks

create redundant chunk 3$e?clusi+e


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!eco+er$ )rom packet loss -%0

%nd 6>C schemepigg$3ack lower8ualit$ stream/send lower resolutionaudio stream asredundant in)ormatione.g. nominalstream 2CM at L k3psand redundant streamQ*M at 14 k3ps.

whene+er there is non"consecuti+e lossrecei+er can conceal the loss.can also append -n"10st and -n"%0nd low"3it ratechunk


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!eco+er$ )rom packet loss -40

nterlea+ing chunks di+ided into smaller units )or e?ample )our 5 msec units

per chunk packet contains small units )rom

di))erent chunks

i) packet lost still ha+e most

o) e+er$ chunk

no redundanc$ o+erhead 3ut

increases pla$out dela$


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Content distri3ution networks -CDNs0

Content replication challenging to stream large )iles

-e.g. +ideo0 )rom single originser+er in real time

solution:replicate content at

hundreds o) ser+ers throughoutnternet content downloaded to CDN

ser+ers ahead o) time placing content close/ to

user a+oids impairments-loss dela$0 o) sendingcontent o+er long paths

CDN ser+er t$picall$ inedgeFaccess network

origin ser+erin North America

CDN distri3ution node

CDN ser+er

in *. America CDN ser+er

in >urope

CDN ser+er

in Asia


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Content distri3ution networks -CDNs0

Content replication CDN -e.g. Akamai0

customer is the contentpro+ider -e.g. CNN0

CDN replicatescustomersE content inCDN ser+ers.

when pro+ider updates

content CDN updatesser+ers

origin ser+er

in North America

CDN distri3ution node

CDN ser+er

in *. America CDN ser+er

in >urope

CDN ser+er

in Asia


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CDN e?ample

origin ser+er -www.)oo.com0

distri3utes ITM= replaces: http:**###foocom*sportsruthgif

withhttp:**###cdncom*###foocom*sports*ruthgif

6!!" re7uest for

###foocom*sports*sportshtml

89 7uery for ###cdncom

6!!" re7uest for

###cdncom*###foocom*sports*ruthgif

1

%

4

origin ser+er

CDNEs authoritati+eDN* ser+er

CDN ser+er near client

CDN compan$ -cdn.com0

distri3utes gi) )iles uses its authoritati+e

DN* ser+er to routeredirect re8uests

client


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More a3out CDNs

routing re8uests CDN creates a map/ indicating distances )rom

lea) *2s and CDN nodes when 8uer$ arri+es at authoritati+e DN* ser+er:

ser+er determines *2 )rom which 8uer$ originates uses map/ to determine 3est CDN ser+er

CDN nodes create application"la$er o+erla$network


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Chapter outline







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2ro+iding Multiple Classes o) *er+ice

thus )ar: making the 3est o) 3est e))ort ser+ice one"sie )its all ser+ice model

alternati+e: multiple classes o) ser+ice partition tra))ic into classes

network treats di))erent classes o) tra))icdi))erentl$ -analog$: ;2 ser+ice +s regular ser+ice0

/111

granularit$:di))erential ser+iceamong multipleclasses not amongindi+idualconnections

histor$: To* 3its


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Multiple classes o) ser+ice: scenario

!1 !%I1

I%

I4

I1.5 M3ps link!1 output

inter)ace8ueue


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*cenario 1: mi?ed 6T2 and audio

>?ample: 1M3ps 2 phone 6T2 share 1.5 M3ps link. 3ursts o) 6T2 can congest router cause audio loss want to gi+e priorit$ to audio o+er 6T2

packet marking needed )or router to distinguish3etween di))erent classes and new router polic$to treat packets accordingl$

2rinciple 1

!1 !%


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2rinciples )or (


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2rinciples )or (


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*cheduling And 2olicing Mechanisms

scheduling:choose ne?t packet to send on link 66< -)irst in )irst out0 scheduling:send in order o)

arri+al to 8ueue real"world e?ample,

discard polic$:i) packet arri+es to )ull 8ueue: who to discard,B Tail drop: drop arri+ing packet

B priorit$: dropFremo+e on priorit$ 3asis

B random: dropFremo+e randoml$


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*cheduling 2olicies: more

2riorit$ scheduling:transmit highest priorit$ 8ueuedpacket multiple classes with di))erent priorities

class ma$ depend on marking or other header in)o e.g. 2sourceFdest port num3ers etc..

!eal world e?ample,


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11: Multimedia Networking 11-/

*cheduling 2olicies: still moreround ro3in scheduling: multiple classes

c$clicall$ scan class 8ueues ser+ing one )rom each class -i) a+aila3le0 real world e?ample,


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*cheduling 2olicies: still more

#eighted 6air (ueuing: generalied !ound !o3in each class gets weighted amount o) ser+ice in each

c$cle

real"world e?ample,


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2olicing Mechanisms

Qoal:limit tra))ic to not e?ceed declared parametersThree common"used criteria o) tra))ic rate: -=ong term0 A+erage !ate:how man$ packets can 3e

sent per unit time -in the long run0

crucial 8uestion: what is the inter+al length: 1&& packets persec or L&&& packets per min ha+e same a+erage@

2eak !ate:e.g. L&&& pkts per min. -ppm0 a+g. 15&&&ppm peak rate

-Ma?.0 Hurst *ie:ma?. num3er o) packets sentconsecuti+el$ -with no inter+ening idle0


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2olicing Mechanisms

Token Hucket:limit input to speci)ied Hurst *ie andA+erage !ate.

3ucket can hold 3 tokens

tokens generated at rate r tokenFsecunless 3ucket )ull o+er inter+al o) length t: num3er o) packets admitted

less than or e8ual to -r t P 30.


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>dge router: per")lowtra))ic management

marks packets as in"pro)ileand out"pro)ile

Core router:

per classtra))ic management

3u))ering and scheduling 3asedon marking at edge

pre)erence gi+en to in"pro)ilepackets

Di))ser+ Architecture

scheduling

.

.

.

r

b

marking


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>dge"router 2acket Marking

class"3ased marking: packets o) di))erent classes markeddi))erentl$ intra"class marking: con)orming portion o) )low marked

di))erentl$ than non"con)orming one

pro)ile: pre"negotiatedrate A 3ucket sie H

packet marking at edge 3ased on per")lowpro)ile

2ossi3le usage o) marking:

Gser packets

!ate A

H


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Classi)ication and Conditioning

2acket is marked in the T$pe o) *er+ice -T


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Classi)ication and Conditioning

ma$ 3e desira3le to limit tra))ic in7ection rate o)some class: user declares tra))ic pro)ile -e.g. rate 3urst

sie0

tra))ic metered shaped i) non"con)orming


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6orwarding -2IH0

2IH result in a di))erent o3ser+a3le -measura3le0)orwarding per)ormance 3eha+ior 2IH does not speci)$ what mechanisms to use to

ensure re8uired 2IH per)ormance 3eha+ior

>?amples: Class A gets ?O o) outgoing link 3andwidth o+er time

inter+als o) a speci)ied length Class A packets lea+e )irst 3e)ore packets )rom class H


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6orwarding -2IH0

2IHs 3eing de+eloped: >?pedited 6orwarding:pkt departure rate o) a

class e8uals or e?ceeds speci)ied rate logical link with a minimum guaranteed rate

Assured 6orwarding: classes o) tra))ic each guaranteed minimum amount o) 3andwidth each with three drop pre)erence partitions


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Chapter outline




.pro+iding multipleclasses o) ser+ice

.5 pro+iding (o*guarantees: nt*er+!*;2


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2rinciples )or (


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(o* guarantee scenario

!esource reser+ation call setup signaling -!*;20 tra))ic (o* declaration per"element admission control

(o*"sensiti+escheduling -e.g.

#6(0

re8uestFrepl$


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>T6 ntegrated *er+ices

architecture )or pro+iding (


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Call Admission

Arri+ing session must : declare its (


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ntser+ (o*: *er+ice models Sr)c%%11 r)c %%1%

Quaranteed ser+ice: worst case tra))ic arri+al:leak$"3ucket"policed source

simple -mathematicall$pro+a3le0 3oundon dela$

S2arekh 1''% Cru 1'UU

Controlled load ser+ice: Va 8ualit$ o) ser+ice closel$appro?imating the (o* thatsame )low would recei+e)rom an unloaded networkelement.V

#6(

token rate r

3ucket sie 3

per")lowrate !

D 3F!ma?

arri+ingtra))ic


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*ignaling in the nternet

connectionless-stateless0

tra))ic )orwarding3$ 2 routers

3est e))ortser+ice

no network

signaling protocolsneeded in initial

2 design

P

New re8uirement:reser+e resources along end"to"endpath -end s$stem routers0 )or (o* )or multimediaapplications

!*;2:!esource !eser+ation 2rotocol S!6C %%&5 allow users to communicate re8uirements to network in

ro3ust and e))icient wa$./ i.e. signaling @


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!*;2 Design Qoals

1. accommodate heterogeneous recei+ers-di))erent3andwidth along paths0

%. accommodate di))erent applications with di))erentresource re8uirements

4. make multicast a )irst class ser+ice with adaptationto multicast group mem3ership

. le+erage e?isting multicastFunicast routing withadaptation to changes in underl$ing unicastmulticast routes

5. control protocol o+erheadto grow -at worst0 linearin W recei+ers

L. modular design)or heterogeneous underl$ingtechnologies


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!*;2: does not

speci)$ how resources are to 3e reser+ed rather: a mechanism )or communicating needs

determine routes packets will take

thatEs the 7o3 o) routing protocols

signaling decoupled )rom routing


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!*;2: o+er+iew o) operation

senders recei+er 7oin a multicast group done outside o) !*;2 senders need not 7oin group

sender"to"network signaling path message:make sender presence known to routers

path teardown: delete senderEs path state )rom routers recei+er"to"network signaling

reser+ation message:reser+e resources )rom sender-s0 torecei+er

reser+ation teardown: remo+e recei+er reser+ations

network"to"end"s$stem signaling path error reser+ation error


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Chapter : *ummar$

2rinciples classi)$ multimedia applications making the 3est o) 3est e))ort ser+ice

2rotocols and Architectures speci)ic protocols )or 3est"e))ort mechanisms )or pro+iding (o* architectures )or (o*

multiple classes o) ser+ice (o* guarantees admission control

ch.11 multimedia and qos

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