# Architecture

## Vocabulary

  - **Fediverse:** several servers following each others
  - **Instance:** a server which runs PeerTube in the fediverse
  - **Origin instance:** the instance on which the video was uploaded and which is seeding (WebSeed protocol) the video
  - **Following:** the action of a PeerTube instance which will follow another instance (subscribe to its videos)

## Base

### Communications
  * All the communications between the instances are signed with [Linked Data Signatures](https://w3c-dvcg.github.io/ld-signatures/) with the private key of the account that made the action
  * We use the [ActivityPub](https://www.w3.org/TR/activitypub/) protocol (only server-server for now). Object models could be found in [shared/models/activitypub directory](https://github.com/Chocobozzz/PeerTube/tree/develop/shared/models/activitypub).
  * All the requests are retried several times if they fail
  * The maximum of points would be defined

### Instance
  * An instance has a websocket tracker which is responsible for all the video uploaded in it
  * An instance has an administrator that can follow other instances
  * An instance can be configured to follow back automatically
  * An instance can blacklist other instances (only used in "follow back" mode)
  * An instance cannot choose which other instance follow it, but it can decide to **reject all** followers
  * After having uploaded a video, the instance seeds it (WebSeed protocol)
  * If a user wants to watch a video, he asks its instance the magnet URI and the frontend adds the torrent (with WebTorrent), creates the HTML5 video player and streams the file into it
  * A user watching a video seeds it too (BitTorrent) so another user who is watching the same video can get the data from the origin server and the user 1 (etc)