issues in offering live p2p streaming service to residential users nazanin magharei, *yang guo, and...
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Issues in Offering Live P2P Streaming Service to Residential Users
Nazanin Magharei, *Yang Guo, and Reza Rejaie
Dept. of Computer and Information Science *Princeton CR Lab University of Oregon Thomson Inc.
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Outline
Introduction and related work PRIME: Mesh-based P2P streaming service Issues in offering p2p streaming to residential users
Effect of available resource Effect of heterogeneous bandwidth Effect of freeloaders Effect of number of users
Conclusions and summary
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Introduction
P2P technique attracting attentions from commercial world NBC Universal goes peer-to-peer – wurldmedia.com BitTorrent raised $8.75 million venture capitals
Teamed with CacheLogic to work for BT Startups providing P2P live program: pplive, coolstreaming BBC IMP Why?
Reduce the cost to compete with piracy
Conceivably provide p2p live streaming in a commercial setting
Using mesh-based p2p streaming
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Introduction
P2P live streaming Tree-based approach
ESM, SplitStream, etc. Mesh-based approach
Coolstreaming, Chainsaw, PRIME, etc. Fundamental difference – static mapping of content to
delivery topology vs. dynamic mapping
Pkt delivery time
Bandwidth variation
Peer degree
Group size
Persistent churn
Batch departure
Mesh
Tree
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Introduction and Related Work
Challenges Heterogeneous access speed – DSL, cable modem, …
Insufficient resource Asymmetric bandwidth – uplink bandwidth < downlink bandwidth Free-loaders
Not willing to contribute Cannot contribute
Behind NAT box or firewall
Key questions What is the impact of available resource to overall performance? How similar (different) is such an effect across peers with different
bandwidth? Whether and how the freeloaders affect the overall performance
and individual received quality?
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PRIME: Mesh-based P2P Streaming Service
Peer expects to receive maximum deliverable quality through its access link
Using MDC in content delivery Two possible performance bottlenecks
Bandwidth bottleneck Insufficient aggregate bandwidth from all parents
Content bottleneck Insufficient useful content from all parents
PRIME attempts to minimize these bottlenecks
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Global Pattern of Content Delivery
Connections in the overlay have roughly the same bandwidth
Group peers into levels, based on their shortest distance from source
Each peer with degree d in level n has at least one parent in level n-1 (diffusion parent) and d-1 parents in the same or lower levels (swarming parents)
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Source
Level 1
Level 2
Level 3
depth
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Global Pattern of Content Delivery
Diffusion phase Peers should receive a
data unit as fast as possible
Swarming phase Peers exchange
(swarm) data units with each other until receive their desired quality of the segment
Level 2
Level 3
Level 1 21 3
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12 13910
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SRC
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Simulation Setting
Evaluated using ns with congestion control Network topology generated using Brite Video rate of 400 kbps, downlink bandwidth of 550 kbps Various resource distribution
Uplin Bw SC1 SC2 SC3 SC4 SC5 SC6
128kpbs 27% 54% 13% 5% 11% 50%
384kpbs 60% 20% 80% 9% 14% 39%
1Mbps 13% 26% 7% 36% 25% 11%
0kbps 0% 0% 0% 50% 50% 0%
RI 1 1 1 1 0.8 0.8
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Effect of Available Resource
Resource Index
Avg
. re
ceiv
ed q
ualit
y
CDF of received quality
Average received quality is proportional to the resource index, however the individual received quality is random
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Effect of Heterogeneous Bandwidth
Avg
. re
ceiv
ed q
ualit
yCDF of received quality
•Bandwidth heterogeneity has no impact on the peers’ received quality•No correlation between received quality and resource contribution
Upload bandwidth
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Effect of Free-loaders
Free-loaders degrade the connectivity between different diffusion trees, hence prevent content swarming and limit delivery quality
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Summary
Two issues identified In resource poor scenarios, the delivered quality to
peers is not correlated to their contribution P2P streaming can handle heterogeneous
bandwidth, however the presence of free-loaders significantly affect the mesh connectivity and degrade delivered quality
Solution: contribution-aware p2p streaming Delivered quality is proportional to contribution Encourage cooperation
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PRIME: Mesh-based P2P Streaming Service
Prior studies often assume a fix peer degree Bandwidth bottleneck only depends on overlay
topology Incoming/outgoing bandwidth of participating peers Incoming/outgoing degree of participating peers
Avg. BW for a connection between parent p and child c
MIN (outbwp/outdegp, inbwc/indegc) All connections in the overlay have roughly the
same bandwidth