Upload
hart
View
28
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Enabling Contribution Awareness in an Overlay Broadcasting System. ACM SIGCOMM 2006. Presented by He Yuan. Outline. Background Related Work Contribution-aware Design Implementation and Experiments Conclusion Discussion. E. D. D. Video Broadcast using Overlay Multicast. Encoder. E. - PowerPoint PPT Presentation
Citation preview
1
Enabling Contribution Awareness in an Overlay Broadcasting
System
ACM SIGCOMM 2006
Presented by He Yuan
2
Outline Background Related Work Contribution-aware Design Implementation and Experiments Conclusion Discussion
3
Video Broadcast using Overlay Multicast
Tokyo
LA
San Francisco
Boston
Pisa
Encoder
E
E
D
D
E
DD: DSLE: Ethernet
PisaTokyo
NYCLA
Boston
San Francisco
Overlay Tree
4
Background I State-of-Art in Overlay Broadcast
Architecture and Protocol Design• Narada, SplitStream, CoopNet, DONet ...
Significant progress in scalability & resiliency
Real Deployments• ESM*, CoolStreaming, PPLive, SopCast ...
5
Background II Much success to date:
Homogeneous environments with abundant bandwidth Heterogeneity in node upload bandwidth
Upload access bandwidth varies widely Hosts may choose to forward differently
Insufficient bandwidth resourceDownload Upload
DSL 600-1200Kbps 64-256KbpsCable 1-6Mbps 128-768KbpsEthernet ≥ 10Mbps ≥ 10Mbps
> 80%
< 20%
6
Related Work Bit-for-bit policy
Effective only in BT-like systems
Differential Admission Control Not feasible in the mainstream Internet
Taxation model
Incentive vs. Fairness
max( * ,0)f t r G
7
Goals and Challenges Goals
Good utilization of bandwidth Differential and equitable distribution Guaranteed QoS
Challenges More generic than bit-for-bit policy Distributed sampling and computing Dynamic environment
8
Contribution-aware Design Assumptions
Multi-tree-based data dissemination
Bandwidth distribution policy
System design
9
Assumptions Abundant download bandwidth Different levels of contribution
Actual contribution fi reflected by Forwarding bound Fi
Non-strategic honest clientsTo encourage a host to relax its Fi
10
Multi-tree-based data dissemination Using MDC, split into T-equally sized stripes T trees, each distributes a single stripe of size S/T Overall quality depends on the number of stripes
received Number of trees node i is entitled to =
/ir
S T
SourceS/3 S/3S/3
S Kbps
Tree 1 Tree 3Tree 2
Peer A
Peer C
11
Bandwidth distribution policy
Entitled bandwidth
0 < α < 1
Contribution∑ fj / N
j
(1 ) ( )i ir f avgf
More generic than bit-for-bit Differential and Equitable Distribution
12
Bandwidth distribution: Example
Source
E
EE ED
D
100Kbps 100Kbps 100Kbps100Kbps
S = 400Kbps T = 4 avg f = 300Kbps α = 0.5
fE = 500Kbps fD = 100Kbps– rE = 0.5*500+0.5*300 = 400Kbps entitled to 4 trees– rD = 0.5*100+0.5*300 = 200Kbps entitled to 2 trees
D D
Entitled NodeExcess Node
13
System Design Distributed System Sampling Computing Number of Entitled Trees
Smoothing Locating Excess Bandwidth
Backoff in Excess Tree Contribution-Aware Node Prioritization
14
Implementation and Experiments
Use Slashdot to evaluate 2 systems: Cont-Agnostic: multi-tree broadcast system Cont-Aware: multi-tree + contribution-aware
heuristics S=400Kbps, T=4, stripe size S/T=100Kbps
2 types of peers: Ethernet fmax ≤800Kbps, DSL fmax ≤100Kbps
HC: 700-800Kbps, LC: 75-100Kbps
Mainstream Internet
Conferences
Broadcast Event
DSL (100Kbp
s)
Ethernet
(10Mbps)
Peak Group Size
SIGCOMM2002
48% 52% 78
SOSP2003 48% 52% 54Rally 75% 25% 481Slashdot 73% 27% 158GrandChallenge
82% 18% 276
15
Evaluation Goals Fairness Overall quality of playback Stability
16
Performance: High Contributors
System Mean Std. DevCont-Agnostic 353 60.9Cont-Aware 415 24.6
Better
Cont-Aware gives HC better performance
17
Performance: Low Contributors
System Mean Std. DevCont-Agnostic 311 80.5Cont-Aware 295 34.8
Similar performance among similar contributors
Better
Better
18
Stability Time between Tree Reductions
Cont-Aware performs slightly worse Reductions => slight dips in quality
Not complete disconnection, 63.4% from 43, 34.1% from 32, only 2.5% from 21 and 10
Reconnection time (in sec)Cont-Aware Cont-Agnostic
HC 7.1 80.82LC 53.42 65.26
Overall 48.25 69.83
19
Performance across traces for high contributors
20
Conclusion Resource-scarce, heterogeneous
environments
Two key ideas: Multi-trees and Linear Taxation
Provide fairness in overlay broadcasting in mainstream Internet environments
21
Discussion Applying MDC to Multi-tree overlay
The issue of redundancy in coding
What’s different in the resulting system? More bandwidth resource or Better QoS Incentive or fairness
Where to go? Customized user requirement
- Demand according to capacity Location-aware streaming reuse technique
22
Thanks!