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Threshold-Based Multicast Threshold-Based Multicast for Continuousfor ContinuousMedia DeliveryMedia Delivery

Lixin GaLixin Gao, Member, IEEE, o, Member, IEEE, and and Don TowsleDon Towsley, Fellow, IEEEy, Fellow, IEEE

IEEE TRANSACTION ON MULTIMEDIA

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OutlineOutline

INTRODUCTIONINTRODUCTION THRESHOLD-BASED MULTICASTTHRESHOLD-BASED MULTICAST OPTIMAL THRESHOLDOPTIMAL THRESHOLD SIMULATION STUDYSIMULATION STUDY CONCUSIONCONCUSION

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INTRODUCTIONINTRODUCTION

Four types of multicast approachesFour types of multicast approaches Server-initiatedServer-initiated

Broadcast video Broadcast video every t minutesevery t minutes Server-initiated-with-prefetching (SIWP)Server-initiated-with-prefetching (SIWP)

PB, PPBPB, PPB … … Client-initiatedClient-initiated

Similar to Similar to BatchBatch Client-initiated-with-prefetching (CIWP)Client-initiated-with-prefetching (CIWP)

Similar to Similar to PatchPatch

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Server-initiatedServer-initiated

No PrefetchNo Prefetch guaranteeguarantee a maximum service latency a maximum service latency Waiting time Waiting time independent to the number of requesindependent to the number of reques

tt With Prefetch (SIWP)With Prefetch (SIWP)

reduce the server network-I/O resources required reduce the server network-I/O resources required Reduce the waiting time moreReduce the waiting time more

Good for Good for hothot video video

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Client-initiatedClient-initiated

No PrefetchNo Prefetch batching reduces demand for server network-I/O bbatching reduces demand for server network-I/O b

andwidthandwidth, but it does so at the cost of introducing s, but it does so at the cost of introducing service latency and there is ervice latency and there is no maximum service latno maximum service latency guaranteeency guarantee

With Prefetch (CIWP)With Prefetch (CIWP) Save server network-I/O bandwidthSave server network-I/O bandwidth Reduce waiting time (in Client-initiated)Reduce waiting time (in Client-initiated)

Good for Good for cold and lukewarmcold and lukewarm video video

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THRESHOLD-BASED THRESHOLD-BASED MULTICASTMULTICAST

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MotivationMotivation

The Server The Server network-I/O bandwidthnetwork-I/O bandwidth Basic CIWPBasic CIWP ：： a linear function of the a linear function of the

request raterequest rate threshold-basedthreshold-based ：： a linear function of a linear function of

the square rootthe square root of the request rate of the request rate

a hybrid of a hybrid of CIWP and SIWPCIWP and SIWP scheme scheme

Cold and lukewarm

Video

Hot Video

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Video delivery system Video delivery system architecturearchitecture

Low Bandwidth

And Reliable

Complete video stream

Partial video stream

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Interaction among client, data Interaction among client, data server, schedulerserver, scheduler

MGc ： complete stream

MGp ： partial stream

VLength ： the number of packets that receive from partial channel

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Client AlgorithmClient Algorithm

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Server Scheduler AlgorithmServer Scheduler Algorithm

1) 1) Batch the request with a complete streamBatch the request with a complete stream o of video that is scheduled to start later.f video that is scheduled to start later.

2) 2) PrefetchPrefetch from an ongoing complete stream from an ongoing complete stream of video and of video and batch a partial streambatch a partial stream of video sc of video scheduled to start later by expanding the partial heduled to start later by expanding the partial stream.stream.

3) 3) PrefetchPrefetch from an ongoing complete stream from an ongoing complete stream of video and of video and schedule a partial streamschedule a partial stream of video of video at the earliest possible time.at the earliest possible time.

4) 4) Schedule a complete streamSchedule a complete stream of video at the of video at the earliest timeearliest time

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1. Batch a complete stream

2. <threshold Prefetch a complete streamBatch a partial stream

3. <threshold Prefetch a complete streamSchedule a partial stream

4.schedule a complete stream

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Data Server AlgorithmData Server Algorithm

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OPTIMAL THRESHOLDOPTIMAL THRESHOLD

requests for video are generated by a Poisson prorequests for video are generated by a Poisson process with cess with mean interarrival timemean interarrival time

We Assume the buffer size is We Assume the buffer size is not a constraintnot a constraint min{ B , Lmin{ B , Lii-B }-B }

：： denote the time at which the system denote the time at which the system schedules a complete stream for video schedules a complete stream for video (renewal p(renewal point)oint)

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OPTIMAL THRESHOLDOPTIMAL THRESHOLDt i-1

t i

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OPTIMAL THRESHOLDOPTIMAL THRESHOLD

: the average server bandwidth: the average server bandwidth

Poisson process

K ： the number of arrivals in Ti

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OPTIMAL THRESHOLDOPTIMAL THRESHOLD

Minimizes the expression

Other Case

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Server bandwith versus request rServer bandwith versus request rateate

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SIMULATION STUDYSIMULATION STUDY

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Expected waiting time versus Expected waiting time versus number of server channels.number of server channels.

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Expected waiting time versus Expected waiting time versus buffer sizebuffer size

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Expected waiting time versus Expected waiting time versus request arrival raterequest arrival rate

Reduces the expected waiting timeReduces the expected waiting time over 4.5 minover 4.5 min compared to FCFS batching compared to FCFS batching over 3.3 minover 3.3 min compared to the basic CIWP compared to the basic CIWP

Even when the request rate Even when the request rate increases to increases to 100 requests per minute100 requests per minute, the expected , the expected waiting time is still waiting time is still less than 1 minless than 1 min in in threshold-based multicast.threshold-based multicast.

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ConclusionConclusion

This paper presents a novel multicast teThis paper presents a novel multicast technique that chnique that significantly reduces the designificantly reduces the demand on the server network-I/O band-wmand on the server network-I/O band-widthidth

Unlike existing CIWP schemes, thresholUnlike existing CIWP schemes, threshold-based multi-cast d-based multi-cast uses a threshold to cuses a threshold to control the frequencyontrol the frequency that a complete vid that a complete video stream is multicastedeo stream is multicasted