Aggressive Prefetching in P2P Live Streaming
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Solution Overview
Problem
Current peer-to-peer (P2P) live streaming systems face inefficiencies due to the shift from push-based RTSP/RTP protocols to pull-based HTTP-live streaming, which requires new approaches to manage data content distribution effectively, especially in reducing delays and source load in P2P networks.
Innovation Solution
A method where a group of peers in a P2P network aggressively request data segments from a streaming source at a higher rate than they are produced, with the first peer to download a segment announcing its availability, allowing other peers to fetch from it instead of the source, thereby reducing delays and source load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If peers request data segments at a rate higher than the streaming source produces them, then playback delay is reduced and source load is decreased, but network bandwidth consumption increases and peer buffer requirements increase
Solution Approach 1:
Peers in the first group make requests for data segments in advance, before the streaming source actually produces them. This aggressive pre-fetching allows segments to be ready for immediate playback, reducing playback delay while the segments are still being produced by the source, thereby decreasing the effective source load.
Solution Approach 2:
The patent introduces an intermediate peer structure where peers in the first group act as intermediaries between the streaming source and other peers. These intermediaries receive segments from the source and redistribute them to other peers, reducing direct source load while managing bandwidth consumption through controlled distribution.
2Productivity
If peers request data segments at a rate higher than the streaming source produces them, then source load is reduced, but network complexity increases due to coordination requirements
Solution Approach 1:
The patent segments peers into different groups based on their role in the distribution network. The first group of peers handles aggressive pre-fetching and redistribution, while other peers consume segments. This segmentation simplifies coordination by assigning specific functions to specific groups, making the complex high-rate request system manageable.
Solution Approach 2:
The system implements feedback mechanisms where peers announce when they have downloaded segments, and the network tracks which segments are available. This feedback allows the system to coordinate the aggressive request rate effectively, knowing which segments are in transit and which are ready, thereby managing coordination complexity.
3Loss of time
If a group of peers aggressively pre-fetches data segments, then playback delay is reduced and source load is decreased, but reliability may be affected due to potential segment loss in high-rate requests
Solution Approach 1:
By making requests in advance before the streaming source produces segments, the system creates a buffer of expected segments in the peer's buffer. This beforehand cushioning ensures that even if some segments are lost during high-rate transmission, playback can continue using the pre-fetched segments, thereby maintaining reliability while reducing delay.
Data Source
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AI summary
The invention relates to methods and devices of distributing data content in a live streaming peer-to-peer (P2P) network. In a first aspect of the present invention a method is provided of distributing data content in a P2P live streaming network comprising a plurality of peers and a streaming source periodically producing segments representing the data content to be distributed, wherein a group of the peers are assigned to download the data content from the streaming source and to distribute the downloaded data content to remaining peers in the P2P network. The method comprises making requests, from a first peer comprised in the group, for a current segment produced by the streaming source, the requests being made at a rate higher than a rate with which the segments are produced by the streaming source. Further, the method comprises announcing, if the first peer is the peer in the group being the first to download the current segment, that the current segment has been downloaded, wherein the network peers can download the current segment from said first peer; or else downloading the current segment from a second peer in the group being the first to download the current segment, which second peer announces the download of the current segment on the P2P network.