LOW-LATENCY VIDEO STREAMING LOW-LATENCY VIDEO STREAMING OVER PEER-TO-PEER NETWORKSOVER PEER-TO-PEER NETWORKSLOW-LATENCY VIDEO STREAMING LOW-LATENCY VIDEO STREAMING OVER PEER-TO-PEER NETWORKSOVER PEER-TO-PEER NETWORKS

Eric SettonEric Setton

Jeonghun NohJeonghun Noh

Professor Bernd GirodProfessor Bernd Girod

Information Systems LaboratoryInformation Systems LaboratoryStanford UniversityStanford University

22J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

MotivationMotivationChallenges of P2P streaming• Limited bandwidth • Unreliable peers

Related work• Tree-based p2p :

– End System Multicast (single tree) [Chu, Rao, Zhang, ACM SIGMETRICS 2000]– COOPNET (central server, multiple trees)

[Padmanabhan et all, NOSSDAV, 2002]

• Mesh-based (Gossip-based) p2p :– Coolstreaming

[Zhang, Liu, Li and Yum, MMSP & INFOCOM 2005]

Our Goal : Low-latency P2P video streaming

33J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

• Low-latency P2P protocol– Join / rejoin procedure– Experimental setup– Performance

• Prioritized transmission– Content / network-aware prioritization– Simulation Results

OutlineOutline

44J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Multiple Tree ConstructionMultiple Tree Construction

… …Video stream

55J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Join ProcedureJoin Procedure

Initial join• Contact video source• Receives peer list, number of trees

Probe peers

Connect to multicast trees• Parent selection factor

– Available bandwidth– Minimize tree height– Maximize diversity

… …Video stream

66J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Disconnect / Rejoin ProcedureDisconnect / Rejoin Procedure

3 trees

Parent of yellow tree is down

Yellow tree is down?

Parent leave is detected

Retransmissions requested

Yellow tree is recovered

77J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Experimental SetupExperimental Setup• Network/protocol simulation in ns-2

– 300 active peers – Random peer arrival/departure

average: ON (4.5 min) / OFF (30 sec)– Typical access bandwidth distribution – Over-provisioned backbone– Delay: 5 ms/link + congestion

• Video streaming– H.264/AVC encoder @ 250 Kb/s– 15 minute live multicast

[Sripanidkulchai et al., 2004]

Downlink Uplink Percentage

512 Kb/s 256 Kb/s 56% 3 Mb/s 384 Kb/s 21%1.5 Mb/s 896 Kb/s 9% 20 Mb/s 2 Mb/s 3% 20 Mb/s 5 Mb/s 11%

Downlink Uplink Percentage

512 Kb/s 256 Kb/s 56% 3 Mb/s 384 Kb/s 21%1.5 Mb/s 896 Kb/s 9% 20 Mb/s 2 Mb/s 3% 20 Mb/s 5 Mb/s 11%

88J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Join and Rejoin LatenciesJoin and Rejoin Latencies

Simulations over ns-2, 300 peers

Number of trees: 3

Retransmissions enabled

Simulations over ns-2, 300 peers

Number of trees: 3

Retransmissions enabled

99J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Protocol ScalabilityProtocol Scalability

Simulations over ns-2

Video traffic

Control traffic

Protocol overhead

Simulations over ns-2

Video traffic

Control traffic

Protocol overhead

1010J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Benefit of DiversityBenefit of Diversity

Downlink Uplink PercentageNumber of average supportable peers

1 tree 2 trees 3 trees 4 trees

512kb/s 256Kb/s 56% 0 0.5 0.7 0.75

3Mb/s 384Kb/s 21% 1 1 1 1.25

1.5Mb/s 896Kb/s 9% 3 3 3 3

20Mb/s 2Mb/s 3% 6 6.5 6.7 6.7

20Mb/s 5Mb/s 11% 17 17 17 17

Number of

average supportable peers2.5 2.8 2.9 3.0

Distribution of peer bandwidth

Video encoding rate : 250 Kb/s

Over-provisioning factor : 15%

Distribution of peer bandwidth

Video encoding rate : 250 Kb/s

Over-provisioning factor : 15%

1111J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Benefit of DiversityBenefit of Diversity

1212J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

• Scheduler iteratively selects

Network / Content-Aware PrioritizationNetwork / Content-Aware Prioritization

Sender

PI B P B P B

7 1 6 1 4 1 2

1313J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Number of trees: 4

Retransmissions enabled

Number of trees: 4

Retransmissions enabled

Network / Content-Aware PrioritizationNetwork / Content-Aware Prioritization

5dB

5dB

4dB

2.5dB

1414J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Network/content aware prioritization33.71 dB

No prioritization30.17 dB

H.264 @ 250 Kb/swith 0.8 second playout deadline

36 Parallel Views out of 75 peers

1515J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Network/content aware prioritization33.71 dB

No prioritization30.17 dB

H.264 @ 250 Kb/swith 0.8 second playout deadline

36 Overlapped Views out of 75 peers

1616J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

ConclusionsConclusions

• Peer-to-peer control protocol– Tested with up to 3000 peers in ns-2– Light-weight and scalable– Low start-up and tree repair time

• Network/content-aware prioritization– Adapts to packet importance and tree topology– Gains up to 5dB with small playout deadline

1717J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Extra Peer Pool for Fast RejoinExtra Peer Pool for Fast Rejoin

Probes extra peers regularly

One of multiple trees

The red tree parent leaves

Chooses a new parent

Advantage : - Keep Parent Diversity - Less packet drop

Disadvantage : - Increased control traffic - Weak to large-scale disconnect

1818J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Receiver-Driven Content-Aware Receiver-Driven Content-Aware Retransmission RequestsRetransmission Requests

• Determine missing packets• Iteratively request most important packet• Limit number of unacknowledged retransmissions

P

PI B B P ……

Parent 1

Parent 2 fails

Video Buffer

Child

1919J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

% peersconnected to all 4 trees

% peersconnected to all 4 trees

With content-oblivious retransmissions

Without retransmissions

Content-Oblivious RetransmissionsContent-Oblivious Retransmissions

2020J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

% peersconnected to all 4 trees

% peersconnected to all 4 trees

With receiver-driven CoDiO light

Without retransmissions

Receiver-Driven Content-Aware Receiver-Driven Content-Aware RetransmissionsRetransmissions

2121J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Video and Network Aware DesignVideo and Network Aware Design

• Child peers (Receivers)– Receive video stream from parent peers– On requesting retransmissions

• Compute expected video quality improvement• Compute expected network congestion

• Parent peers (Senders)– Send video stream to child peers– On scheduling packets to transmit

• Compute importance of each packet• Compute expected network delay

2222J. Noh et al. : Low Latency Video Streaming Over Peer-To-Peer Networks July 10 2006

Benefit of DiversityBenefit of Diversity

Video source : 250kbps (Mthr & Dthr)

Retransmissions enabled

Video source : 250kbps (Mthr & Dthr)

Retransmissions enabled