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.

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

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

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

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?

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

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

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

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

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

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

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

Effect of Number of Users

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

Backup Slides

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

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