Measure and Model P2P Streaming System by Buffer Bitmap

Yishuai Chen*, Changjia Chen, Chunxi Li Network Research Group, Telecom Lab, Beijing Jiaotong University

Index

Introduction Measurement of PPLive Analysis Modeling

Mesh-Based P2P Streaming System

Media Server

Service Provider

User 1

User 2

User 3

User 4Chunk 1:

Chunk 2

Local Buffer

For local playback Sliding window like Limited Size

10s-100s

Buffer & Buffer Bitmap

Measurable

Virtual Buffer

End: Media Server Contain: the newest uploaded chunk

Head: Peer buffer head Contain: the chunk shall be rejected

Bitmap of virtual buffer: Peer’s buffer bitmap + ‘0’ appended until the buffer end

Measurement of PPLive Behavior:

cache rejection sync with media server’s chunk uploading

Rejection rate of a chunk = its uploading rate at media server

Theorem 1. A fixed-duration buffer When constant rate uploading, fixed length

buffer Smoothly transit when rate changes

Analysis Method

Bitmap Matrix

Chunk Position: m Occupancy Probability: Pm

Pm: is a network characteristicPeers in same network has similar Pm

N(t) chunk uploaded at t=0 N(t) ： the amount of peers who have

obtained this chunk at time t Reflects the propagation procedure of a

chunk Pm = N(m/r)/M0

M0 : network size r : playback rate.

Model

Two phases

Each phase is exponential

Model Verification

Thanks!