Video On Demand 1 Video on Demand One

Video On Demand 1

Video on Demand One video server l Many video data l Many clients l Client want to watch at any time l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 2

Assumptions Constant bitrate stream l Perfect network transport l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 3

Unicast Solution One channel per client l No start-up latency l No client buffer l Low client bandwidth l Large server bandwidth l Not scalable l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 4

Multicast Solution l Batching l l l 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. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 5

Multicast Solution l User-centered approach l l Scheduling data based on user requests Data-centered approach Don’t care about user l Just broadcast popular video l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 6

Multicast Solution Batching l Staggered Broadcast l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 7

Staggered Broadcast Video C 0 C 1 C 2 : NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 8

Staggered Broadcast 2 hour video l 5 minutes waiting time l Number of channels = 2 x 60 / 5 = 24 l l Required bandwidth = 1. 5 Mbps x 24 = 36 Mbps NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 9

Multicast Solution Batching l Staggered Broadcast l clients have to wait l No client buffer l Low client bandwidth l Huge server bandwidth l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 10

Multicast Solution Batching l Staggered Broadcast l Periodic Broadcast l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 11

Periodic Broadcast Video C 0 C 1 C 2 : NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 12

Pyramid Broadcast Video C 0 C 1 C 2 : NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 13

Pyramid Broadcast Video C 0 C 1 C 2 : NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 14

Analysis of Pyramid Broadcast l Notations l l l 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. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 15

Channel Bandwidth playback time = Ti i i+1 D’oh! Just miss it! i+1 download time = Ti+1 Bv/Bi Download time for segment i+1 needs to be smaller than Ti for it to arrive in time. NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 16

Channel Bandwidth NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 17

=2 NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 18

Start-up Latency l Worst case waiting time = NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 19

Optimal T 1 2. 5 NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 20

Storage Requirements NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 21

Pyramid Broadcast l Large client bandwidth ( KBv) l Huge client buffer (70– 80% Tv) NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 22

Permutation-based Pyramid Broadcast C 0 C 1 C 2 NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 23

Channel Bandwidth playback time = Ti i i+1 D’oh! Just miss it! i+1 X i+1 download time = Ti+1 Bv/Bi X needs to be smaller than Ti for segment i+1 to arrive in time. NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 24

Channel Bandwidth NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 25

Client Latency NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 26

Storage Requirement One channel at a time l Can pause and wait l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 27

Storage Requirement pause k-1 k resume k Within time X, better not consume all data in buffer. X NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 28

Storage Requirement pause k-1 k k resume Within time X, better not consume all data in buffer. X NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 29

Storage Requirement NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 30

Comparisons Scheme Pyramid Storage Server’s BW KBv 70% Pyramid++ 20% ( +p)KBv Client’s BW 4 -5 Bv 2 -3 Bv Carter, Long and Paris “Video on Demand Broadcasting Protocols” NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 31

Pyramid Broadcasting NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 32

Skyscraper Broadcasting l Observations: l storage requirement is affected by size of the largest chunk So, let’s limit the size of the largest chunk! NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 33

Pyramid NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) Skyscraper 34

Skyscraper Broadcasting l Uses series 1 2 2 5 5 12 12 25 25 52 52 … W W W NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 35

Skyscraper Example NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 36

Skyscraper Example NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 37

Comparisons Scheme Pyramid Storage Server’s BW KBv 70% Client’s BW 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. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 38

Other schemes l Pagoda Broadcasting 1 3 5 15 25 75 125 … l Harmonic Broadcasting Equal segment size, varies bandwidth instead! NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 39

Multicast Solution Batching l Staggered Broadcast l Periodic Broadcast l Sending rate ≥ playback rate l May need multiple channels l Need additional client buffer l Need to wait l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 40

Multicast Solution Batching l Staggered Broadcast l Periodic Broadcast l Patching l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 41

Patching Time mcast unicast Client Request NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 42

Patching Window: W Time mcast Client Request NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 43

Grace Patching if W < B client buffer video[W. . end] l 30 minutes video l 1 client arrival per minute l Total data delivered = NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 44

Scenario 1: B = 15 mins 30 minutes video l 1 client arrival per minute l Total data delivered = l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 45

Scenario 2: B = 5 mins 30 minutes video l 1 client arrival per minute l Total data delivered = l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 46

Scenario 3: B = 2 mins 30 minutes video l 1 client arrival per minute l Total data delivered = l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 47

Summary Batching (User Centered) l Staggered Broadcast (Data Centered) l Periodic Broadcast (Data Centered) l Patching (True VOD) l NUS. SOC. CS 5248 -2010 Roger Zimmermann (based in part on slides by Ooi Wei Tsang) 48