Peercasting is a method of
multicast
In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast should not be confused wi ...
ing
streams
A stream is a continuous body of surface water flowing within the bed and banks of a channel. Depending on its location or certain characteristics, a stream may be referred to by a variety of local or regional names. Long large streams a ...
, usually audio and/or video, to the
Internet
The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, p ...
via
peer-to-peer
Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers. Peers are equally privileged, equipotent participants in the network. They are said to form a peer-to-peer ...
technology. It can be used for commercial, independent, and amateur multicasts. Unlike traditional
IP multicast
IP multicast is a method of sending Internet Protocol (IP) datagrams to a group of interested receivers in a single transmission. It is the IP-specific form of multicast and is used for streaming media and other network applications. It uses speci ...
, peercasting can facilitate
on-demand content delivery.
Operation
Peercasting usually works by having peers automatically relay a stream to other peers. The P2P
overlay network
An overlay network is a computer network that is layered on top of another network.
Structure
Nodes in the overlay network can be thought of as being connected by virtual or logical links, each of which corresponds to a path, perhaps through ...
helps peers find a relay for a specified stream to connect to. This method suffers from poor quality of service during times when relays disconnect or peers need to switch to a different relay, referred to as "churn".
Another solution used is minute swarming, wherein a live stream is broken up into minute length files that are swarmed via P2P software such as
BitTorrent or Dijjer. However, this suffers from excessive overhead for the formation of a new swarm every minute.
A new technique is to stripe a live stream into multiple substreams, akin to
RAID
Raid, RAID or Raids may refer to:
Attack
* Raid (military), a sudden attack behind the enemy's lines without the intention of holding ground
* Corporate raid, a type of hostile takeover in business
* Panty raid, a prankish raid by male college ...
striping.
Forward error correction
In computing, telecommunication, information theory, and coding theory, an error correction code, sometimes error correcting code, (ECC) is used for controlling errors in data over unreliable or noisy communication channels. The central idea i ...
and timing information is applied to these substreams such that the original stream can be reformed using at least all but one of the substreams (
fountain code In coding theory, fountain codes (also known as rateless erasure codes) are a class of erasure codes with the property that a potentially limitless sequence of encoding symbols can be generated from a given set of source symbols such that the orig ...
s are an efficient way to make and combine the substreams). In turn, these streams are relayed using the first method.
Another solution is to permit clients to connect to a new relay and resume streaming from where they left off by their old relay. Relays would retain a back buffer to permit clients to resume streaming from anywhere within the range of said buffer. This would essentially be an extension to the
Icecast
Icecast is a streaming media project released as free software maintained by the Xiph.Org Foundation. It also refers specifically to the server program which is part of the project. Icecast was created in December 1998/January 1999 by Jack Mo ...
protocol.
Software used for peercasting
Free and open source software
*
Alluvium (peercasting)
*
Tribler
*
PULSE
In medicine, a pulse represents the tactile arterial palpation of the cardiac cycle (heartbeat) by trained fingertips. The pulse may be palpated in any place that allows an artery to be compressed near the surface of the body, such as at the n ...
Proprietary
*
Ace Stream
*
PPStream
*
Rawflow
*
Red Swoosh
Red Swoosh was a peer-to-peer file sharing company founded by Travis Kalanick and Michael Todd in 2001 and acquired by Akamai Technologies in 2007. The Red Swoosh technology included a centralized directory that indexed online clients and cache ...
*
Veoh
See also
*
Broadcatching
Broadcatching is the downloading of digital content that has been made available over the Internet using RSS.
The general idea is to use an automated mechanism to aggregate various web feeds and download content for viewing or presentation purpose ...
*
Comparison of streaming media systems
*
P2PTV
P2PTV refers to peer-to-peer (P2P) software applications designed to redistribute video streams in real time on a P2P network; the distributed video streams are typically TV channels from all over the world but may also come from other sources. T ...
*
TVUnetworks
*
Wireless ad hoc network
References
{{reflist
Digital audio
File sharing
Technology neologisms
Peer-to-peer computing