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CacheTorrent GoDoc

The general idea of the CacheTorrent protocol is assigning the role of leaders to a percent of the peers. Each Leader will act as a unidirectional cache for downloading in each autonomous system. On one hand, a Follower will have to connect to a Leader in order to download a piece. On the other hand, a Follower can upload directly to another Leader in a different autonomous system.

Implementation

We extend the BitTorrent protocol by adding components on top of it. We decorate a BitTorrent Peer as follows:

  • Peer - a CacheTorrent wrapper over a BitTorrent peer; it has a node filed
  • Leader - a wrapper over a BitTorrent peer and it can sit on top of a node field
  • Follower - a wrapper over a BitTorrent peer and it can sit on top of a node field

The Follower does not have many modifications, having less capabilities. The Leader replaces has the following components:

  • CacheDownload - a Download components which forwards uses a Forwarder and a Picker
  • CacheUpload - an upload component which uploads only if it has the piece
  • Picker - a wrapper over a BitTorrent Picker which selects a piece for a Leader by taking into consideration the requests made by Followers
  • Forwarder - a structure which forwards messages received by a Leader towards its followers

To see more implementation details, take a look at the godoc.

Message Types

Besides the BitTorrent message types, we have the following new messages:

  • LeaderStart - message used to establish an indirect connection(connection to another peer through a Leader)
  • Neighbours - similar to Neighbours message in BitTorrent protocol
  • Candidate - message used by a peer to become a candidate in leader election
  • Leader - message sent by the Tracker to announce the leaders