Peer to Peer Streaming Protocol

Document Charter Peer to Peer Streaming Protocol WG (ppsp) Snapshot
Title Peer to Peer Streaming Protocol
Last updated 2010-03-22
State Approved
WG State Concluded
IESG Responsible AD Martin Stiemerling
Charter Edit AD (None)
Send notices to (None)


The Peer-to-Peer Streaming Protocol (PPSP) working group develops two
  signaling and control protocols for a peer-to-peer (P2P) streaming
  system for transmitting live and time-shifted media content with near
  real-time delivery requirements.
  Two kinds of nodes exist in the targeted P2P streaming system, i.e.,
  "peers" and "trackers". Peers are nodes that are actively sending and
  receiving streamed media content, and include both statically connected
  hosts as well as mobile devices with connectivity and IP addresses that
  change over time. The set of peers that are participating in a streaming
  session will dynamically change over time. Trackers are well-known nodes
  with stable connectivity that maintain meta information about the
  streamed content and the dynamic peer set. Trackers can be organized in
  centralized or distributed ways.
  The PPSP WG designs a protocol for signaling and control between
  trackers and peers (the PPSP "tracker protocol") and a signaling and
  control protocol for communication among the peers (the PPSP "peer
  protocol"). The two protocols enable peers to receive streaming data
  within the time constraints required by specific content items. The
  tracker protocol handles the initial and periodic exchange of meta
  information between trackers and peers, such as peer lists and content
  information. The peer protocol controls the advertising and exchange of
  media data availability between the peers.
  It is envisioned that the tracker protocol will be modeled as a
  request/response protocol between peers and trackers, and will carry
  information needed for the selection of peers suitable for real-time
  streaming. The peer protocol is envisioned to be modeled as a
  gossip-like protocol with periodic, pairwise exchanges of neighbor and
  media chunk availability information. Both protocols will be carried
  over TCP (or UDP, when delivery requirements cannot be met by TCP),
  likely in combination with ICE for NAT traversal support. Perfect
  privacy protection is a good feature to have but not a mandatory
  requirement for the peer and tracker protocols. The WG will consider to
  use existing protocols as design base for the tracker and peer
  Developing mechanisms for searching trackers that contain a specific
  media item is out of the scope of this WG. Additionally, the WG will
  work under the assumption that trackers are logically centralized
  entities (e.g., a single server or a server farm performing DNS-based
  local balancing). However, as far as it is possible, the WG will not
  make design decisions that could preclude the use of distributed
  trackers in the future (e.g., DHT-based trackers).
  A peer looking for a media chunk uses the tracker and peer protocols to
  locate a remote peer (or peers) that can provide it with that media
  chunk. Obtaining the media chunk from the remote peer will involve some
  type of signaling exchange plus the actual media transfer. The first
  task for this WG will be to decide which signaling and media transfer
  protocols will be used. The WG will consider existing protocols and, if
  needed, identify potential extensions to these protocols. The WG will
  consider the interactions between these protocols and the peer protocol
  (e.g., avoiding duplicate NAT traversal procedures). Examples of
  signaling protocols to be considered are SIP, RTSP, and HTTP. Examples
  of media transfer protocols to be considered are RTP and HTTP.
  PPSP is not chartered to work on media transmission protocols, media
  encoding techniques or other components of a P2P streaming system such
  as playout, scheduling and control, etc.
  The work items of the PPSP WG are:
  (1) A "problem statement" document that gives an overview of the
  proposed P2P streaming system, motivates the desire for
  standardized protocols, defines the envisioned scope of those
  standardized components and discusses common terminologies and
  (2) A "requirements" document that details the specific functional,
  operational and performance requirements of the two PPSP
  (3) An "architectural survey" document that summarizes current P2P
  streaming architectures, in particular tracker-based P2P
  streaming systems, and highlights best current practices.
  (4) A detailed specification of the PPSP peer protocol.
  (5) A detailed specification of the PPSP tracker protocol.
  (6) A "usage guide" that describes how the two PPSP protocols and
  existing IETF protocols, such as P2PSIP or ALTO, can be combined
  to create a deployable operational P2P streaming system. This
  document may also discuss variants of such a system that, for
  example, use layered media encoding and related media chunk
  descriptions in the peer protocol for more robust streaming.
  The work items of the PPSP WG interacts with the work performed in other
  Whenever extensions or modification to the protocols developed in other
  WGs are deemed necessary, PPSP shall communicate and discuss the
  requirements for such extensions with the relevant WGs. PPSP is not
  chartered to design and specify such changes.