D-LAN

h1. Protocols

This page describes the protocols used by Aybabtu for network communication between cores and between core and GUI.

h2. Core <-> Core

h3. Notes pour plus tards

* Le message _HaveChunks_ doit être multicast et la réponse est un datagramme UDP. Il n'est pas possible de maintenir N-1 connexion TCP en permanence ou N est le nombre de peer. (à mesurer). DU coup ce message peut remplacer le _IMAlive_

See source:protos/network_protocol.proto for message details.

There is no more than one downloading from B to A. A peer which a download is active is setted as not free.

There is _NbDownloadThread_ thread T. Each thread will choose a free chunk and download it. Here is the thread loop.

<pre>

take the first file not finished -> f

for each chunk not download or not being downloaded takes the best one :

   c has a free peer -> p and p.downloadRate is the best.

   If there is some equals chunk, T will choose randomly among theses.

   If there is no free chunk then go to the next file.

   If the hash chunks of a file are unknown then the hashes are asked to the source, see the message _GetHashes _.

</pre>

h3. Parameters

Most parameters will be stored as constants in their component.

|_.Name|_.Value |_.Unit|_.Explanation/Comments|

| _IMAliveFrequency_ | 0.1 | [Hz] | The message _IMAlive_ is sent each 10s. |

| _ChunkSize_ | 33554432 | [Byte] | (32 MB) |

| _LanSpeed_ | 52428800 | [Byte/s] | (50 MB/s) |

| _TimeRecheckChunkFactor_ | 4 | - | If the time to download a chunk exceeds _TimeRecheckChunkFactor_ * _ChunkSize_ / _LanSpeed_ the peers are rescanned to choose a better one (better download rate). For example : 4 * 32 / 50 = 2.6 second |

| _SwitchToAnotherPeerFactor_ | 1.5 | - | During the recheck of the peers to choose a better one the other download rate must be above the current * 1.5. |

| _DownloadRateValidTime_ | 1500 / _LanSpeed_ = 300 s | [s] | (5 min). The download rate of a peer is only valid during this time after its last update. After that its rate is set to the maximum. | 

| _TimeBetweenChunksUpdate_ | 500 / _LanSpeed_ = 10 s | [s] | Each 10 s a daemon will scan the _NumberOfChunkToUpdate_ first chunks from the first queued downloads to know which peer has which chunk. |

| _NumberOfChunkToUpdate_ | 100 * _LanSpeed_ / _ChunkSize_ = 156 | - | The first 156 hash chunks (3 kB) will by send periodically to each peer. See message _HaveChunks_ in the proto file. |

| _FindTimeout_ | 15 | [s] | A search request is abandoned after 15 seconds from the start of the request. See message _Find_. |

| _GetHashesTimeout_ | 200 | [s] | Timeout for the message _GetHashes_. |

| _GetChunkTimeout_ | 10 | [s] | Timeout for the message _GetChunk_. |

| _HaveChunksTimeout_ | _TimeBetweenChunksUpdate_ = 10 | [s] | Timeout for the message _HaveChunks_. |

| _GetEntriesTimeout_ | 10 | [s] | Timeout for the message _GetEntries_. |

| _NbDownloadThread_ | 3 | - | Number of concurrent downloading thread. |

h2. Core <-> GUI