a hybrid video streaming scheme on hierarchical p2p networks · on hierarchical p2p networks...

Feb. 22, 2005 EuroIMSA 2005 1

A Hybrid Video Streaming Scheme on Hierarchical P2P Networks

�Shinsuke SuetsuguNaoki Wakamiya, Masayuki Murata

Osaka University, Japan

Koichi Konishi, Kunihiro TaniguchiNEC Corporation, Japan

Feb. 22, 2005 EuroIMSA 2005 2

Overview

n Research backgroundn Objectiven Proposed scheme

• Scheduling algorithm• Tree construction mechanism• Fault recovery mechanism

n Simulation experimentsn Conclusion & future work

Feb. 22, 2005 EuroIMSA 2005 3

Research Background (1/2)n Increased popularity of video streaming

• streaming: to decode while downloading• distribution of movies or news

n Development of P2P technology• distribute video streaming with P2P multicast• reduce load of servers

Server

Client PeerServer

P2P multicast

constructdistribution

tree

Client-server model

Feb. 22, 2005 EuroIMSA 2005 4

Research Background (2/2)

n How to construct “good” distribution trees?• one way is to measure characteristics of

physical networks, such as delay or bandwidthn requires long time n causes heavy load

• enterprises or universities: well-organized networks are constructed

n branch networks or division networksn no need to measure characteristicsn construct distribution trees easily and quickly

Feb. 22, 2005 EuroIMSA 2005 5

Objectiven We propose a hybrid video streaming scheme

for…• networks hierarchically constructed based on

organization structure • networks with thousands or ten thousands of users

n Objective of our proposal• reduce load of servers• reduce load of networks

n avoid connecting between long-distance peersn avoid using a link repeatedly for a flow

• reduce initial waiting time until video starts playing• reduce freeze time caused by faults

Feb. 22, 2005 EuroIMSA 2005 6

Overview of Proposed Scheme

Tree Server(GTS)

Video Server(ORG)

SchedulingServer(SS)

Local Tree Server (LTS)

Subnet Tree Server (STS)

Normal Peer�NP�

branch A

branch C

branch B

subnet a

subnet c

subnet b

Central office

branch

branch

branch

division

division

division

Feb. 22, 2005 EuroIMSA 2005 7

Outline of Proposed Scheme��Scheduling algorithm

• use “pyramid broadcasting”→ reduce initial waiting time until video starts playing

��Tree construction mechanism• construct P2P multicast trees

→ reduce load of servers• make networks hierarchical based on physical structure

→ reduce load of networks

��Fault recovery mechanism• recover from faults rapidly with only local

communication→ reduce freeze time caused by fault

Feb. 22, 2005 EuroIMSA 2005 8

��Scheduling Algorithm- pyramid broadcasting -

�

�

playout →video data

Scheduling Server �SS�

Video Server�ORG�

play-rate b

transmission –rate 2b

distribute continuously on different channelsamong each segments

segment

slot

peer

� � � � �

Feb. 22, 2005 EuroIMSA 2005 9

��Tree Construction Mechanism

trees are constructed segment-by-segment and slot-by-slot

Feb. 22, 2005 EuroIMSA 2005 10

��Tree Construction Mechanism- inter-branch tree -

Tree Server�GTS�


LTS

inform IP address of Video Server

LTS

participation request

The first participation request in this

branch

branch A

branch C

branch B

Central office

Feb. 22, 2005 EuroIMSA 2005 11

��Tree Construction Mechanism- inter-branch tree -



branch A

branch C

branch B

limitation for number of childrenfanout = 2

list of ancestors: video server → LTS B

recursively attempts to connect to children on failure

inform IP address of one of its children

Peers store informed addresses as a list of ancestors

Central office

Feb. 22, 2005 EuroIMSA 2005 12

��Tree Construction Mechanism- inter-subnet tree -

LTS

STS



consider its fanout

branch A

subnet A

subnet D

subnet B

subnet C

inform IP address of LTS in this branch

Feb. 22, 2005 EuroIMSA 2005 13

�� Tree Construction Mechanism- inter-NP (Normal Peer) tree -

n difference between 1st and later segments

NP

inform IP address of STS in this subnet

1st segment

STS

later segment

access STS of previous segment directly without Tree

Server


consider its fanout

subnet A

Feb. 22, 2005 EuroIMSA 2005 14

��Fault Recovery Mechanism- recovery within subtree -

n Fault:• peer leaves network

n variety of reasonsn different occasions

n �ecovery within subtree• each peer has information

about ancestors• mechanism can be applied

in the same manner to:n inter-branch treesn inter-subnet treesn inter-NP trees

connectionrequest

consider fanout

limitation

recoveryconnection request

Inform address

connection request

Feb. 22, 2005 EuroIMSA 2005 15

Simulation Experimentsn Evaluation criteria

• load of servers and peers • initial waiting time• recovery and freeze time

n Scenario• 5 branches and 5 subnets in a branch• peer arrival process: uniform, average: 30 [arrivals/sec]

→ average total number of peers: 2,790• transmission delay between server and peer: 200 [ms]• transmission delay between peers: 20 [ms]• fanout degree: 3• fault probability: 0.004

(= 47% for correctly receiving the whole video)• video duration: 186 [sec]• number (lengths) of segments: 5 �6, 12, 24, 48, 96 [sec]�

Feb. 22, 2005 EuroIMSA 2005 16

Initial Waiting Time

average waiting time: 2.94 secmaximum waiting time: < 6 sec

initial waiting time [sec]

cum

ulat

ive

prob

abili

ty

Feb. 22, 2005 EuroIMSA 2005 17

Freeze Time

video freezes for only 0.5 % of all thousands of peers

maximum freeze time: < 1 sec

freeze time [sec]

cum

ulat

ive

prob

abili

ty

Feb. 22, 2005 EuroIMSA 2005 18

Conclusion & Future Work

n Proposal of video streaming distribution scheme

n Scheduling algorithmn Tree construction mechanismn Fault recovery mechanism

• Reduction of initial waiting time and freeze time

n Extensions• Further reduction of load on the tree server• Optimization of tree structures to eliminate

long-distance redundant links

Feb. 22, 2005 EuroIMSA 2005 19

n Thank you.

a hybrid video streaming scheme on hierarchical p2p networks · on hierarchical p2p networks...

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