2. 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.

3. 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

4. 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

5. 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

6. 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?

7. 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

8. 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)
Source 1 3
Level 1 2
Level 2
depth 4 6 5 7 10 12 8 13 9 11
Level 3

9. 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
SRC
Level 1 1 3 2
Level 2 4 6 5 7 10
Level 3 12 8 13 9 11

10. 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
26% 7%
36%
25%
0kbps 0% RI 1
0.8

11. Effect of Available Resource
Avg. received quality
Resource Index
CDF of received quality
Average received quality is proportional to the resource index, however the individual received quality is random

12. Effect of Heterogeneous Bandwidth
Avg. received quality
CDF of received quality
Upload bandwidth
Bandwidth heterogeneity has no impact on the peers’ received quality
No correlation between received quality and resource contribution

13. Effect of Free-loaders
Free-loaders degrade the connectivity between different diffusion trees, hence prevent content swarming and limit delivery quality

14. Effect of Number of Users

15. 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

16. Backup Slides

17. Global Pattern of Content Delivery
SRC
Level 1 1 3 2
Level 2 4 6 5 7 10
Level 3 12 8 13 9 11

18. 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