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Video On Demand

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Video on Demand

One video serverMany video dataMany clientsClient want to watch at any time

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Assumptions

Constant bitrate streamPerfect network transport

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Unicast Solution

One channel per clientNo start-up latencyNo client bufferLow client bandwidthLarge server bandwidth Not scalable

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Multicast Solution

Batching aggregate client requests serve using multicast clients have to wait No client buffer Low client bandwidth

“Scheduling Policies for an On-Demand Video Server

with Batching”

Dan, Sitaram, Shahabuddin, IBM

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Multicast Solution

User-centered approachScheduling data based on user requests

Data-centered approachDon’t care about userJust broadcast popular video

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Multicast Solution

BatchingStaggered Broadcast

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Staggered Broadcast

Video

C0

C1

C2

:

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Staggered Broadcast

2 hour video5 minutes waiting timeNumber of channels =

2 x 60 / 5 = 24

Required bandwidth =

1.5Mbps x 24 = 36Mbps

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Multicast Solution

BatchingStaggered Broadcast

clients have to waitNo client bufferLow client bandwidthHuge server bandwidth

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Multicast Solution

BatchingStaggered BroadcastPeriodic Broadcast

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Periodic Broadcast

Video

C0

C1

C2

:

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Pyramid Broadcast

Video

C0

C1

C2

:

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Pyramid Broadcast

Video

C0

C1

C2

:

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Analysis of Pyramid Broadcast

Notations B : Total available bandwidth Bv : Bandwidth of video

Tv : Total length of each video K : Number of segments per video

Ti : Length of segment i : Factor in geometric series

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Channel Bandwidth

i

i+1 i+1

playback time = Ti

download time = Ti+1Bv/Bi

Download time for segment i+1 needsto be smaller than Ti for it to arrive in time.

D’oh!Just miss it!

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Channel Bandwidth

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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= 2

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Start-up Latency

Worst case waiting time =

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Optimal

2.5

T1

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Storage Requirements

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Pyramid Broadcast

Large client bandwidth (KBv)

Huge client buffer (70–80% Tv)

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Permutation-based Pyramid Broadcast

C0

C1

C2

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Channel Bandwidth

i

i+1 i+1

playback time = Ti

download time = Ti+1Bv/Bi

X needs to be smaller than Ti for segment i+1 to arrive in time.

D’oh!Just miss it!

i+1 i+1

X

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Channel Bandwidth

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Client Latency

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Storage Requirement

One channel at a timeCan pause and wait

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Storage Requirement

k-1

k

k

k-1

pause

resume

X

Within time X, betternot consume all data in buffer.

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Storage Requirement

k-1

k

k

k-1

pause

resume

X

Within time X, betternot consume all data in buffer.

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Storage Requirement

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Comparisons

Scheme Storage Server’sBW

Client’sBW

Pyramid 70% KBv 4-5 Bv

Pyramid++ 20% (+p)KBv 2-3 Bv

Carter, Long and Paris “Video on Demand Broadcasting Protocols”

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Pyramid Broadcasting

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Skyscraper BroadcastingObservations:

storage requirement is affected by size of the largest chunk

So, let’s limit the size of the largest chunk!

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Pyramid Skyscraper

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Skyscraper BroadcastingUses series

1 2 2 5 5 12 12 25 25 52 52 … W W W

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Skyscraper Example

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Skyscraper Example

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Comparisons

Scheme Storage Server’sBW

Client’sBW

Pyramid 70% KBv 4-5 Bv

Pyramid++ 20% (+p)KBv 2-3 Bv

Skyscraper

10% KBv 1-2 Bv

Carter, Long and Paris “Video on Demand Broadcasting Protocols”

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Other schemes

Pagoda Broadcasting 1 3 5 15 25 75 125 …

Harmonic BroadcastingEqual segment size, varies bandwidth instead!

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Multicast Solution

BatchingStaggered BroadcastPeriodic Broadcast

Sending rate ≥ playback rateMay need multiple channelsNeed additional client buffer

Need to wait

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Multicast Solution

BatchingStaggered BroadcastPeriodic BroadcastPatching

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Patching

Time

Client Request

mcast

unicast

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Patching

Time

Client Request

Patching Window: W

mcast

mcast

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Grace Patching

if W < Bclient buffer video[W .. end]

30 minutes video1 client arrival per minuteTotal data delivered =

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Scenario 1: B = 15mins30 minutes video1 client arrival per minuteTotal data delivered =

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Scenario 2: B = 5mins

30 minutes video1 client arrival per minuteTotal data delivered =

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Scenario 3: B = 2mins

30 minutes video1 client arrival per minuteTotal data delivered =

NUS.SOC.CS5248-2010Roger Zimmermann (based in part on slides by Ooi Wei Tsang)

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Summary

Batching (User Centered)Staggered Broadcast (Data

Centered)

Periodic Broadcast (Data Centered)

Patching (True VOD)