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Aion-P2p-Specifications.md

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Introduction

Aion network p2p protocols define set of messages which provide foundation rules of peer to peer communication fit for aion network and development progresses.

Node example

  • endpoint: p2p://{uuid}@{ip}:{port}

Header src

Header specific how to encode / decode message. For each protocol there would be pair of message and handler to be constructed by same header instance which indicates same version, control and action.

  • length - byte[8]
  • includes
    1. version - byte[2]
      • Aion test net zero is using version 0.
    2. control - byte
    3. action - byte
    4. body len - byte[4]
      • Max body length is 400 MB per message on current setting. Any message exceeds max length should not be delivered to body read routine.
|<-    version    ->|<- ctrl->|<- act ->|<-             body len              ->|       
---------------------------------------------------------------------------------
|    0    |    1    |    2    |    3    |    4    |    5    |    6    |    7    |  
---------------------------------------------------------------------------------

Message src

Message exchanged by peers contains 2 part, header and body.

  • header byte[8]
  • body byte[]

Route Table

route function return (ver << 16) | (ctrl << 8) | action;

m - module, v - version, c - control, a - action

m v c a message attributes description
p2p 0 0 0 DISCONNECT disconnect
0 0 1 REQ_HANDSHAKE nodeId byte[36]
version byte[4]
ip byte[8]
port byte[4]
revisionLen byte
revision byte[]		 request handshakeversion - self supported version
0 0 2 RES_HANDSHAKE byte response handshake
0x01 true
0x00 false
0 0 3 PING ping
0 0 4 PONG pong
0 0 5 REQ_ACTIVE_NODES request active nodes
0 0 6 RES_ACTIVE_NODES List<Node> src response active nodes
0 0 127 UNKNOWN drop message
sync 0 1 0 REQ_STATUS request status
0 1 1 RES_STATUS bestBlockNumber byte[8]
totalDifficultyLen byte
totalDifficulty byte[]
bestHash byte[32]
genesisHash byte[32]
 response status
0 1 2 REQ_BLOCKS_HEADERS fromBlock byte[8]
take byte[4]		 request blocks headers
0 1 3 RES_BLOCKS_HEADERS List<A0BlockHeader> (rlp) src response blocks headers
0 1 4 REQ_BLOCKS_BODIES List<byte[32]> request blocks bodies
0 1 5 RES_BLOCKS_BODIES List<byte[]> (rlp) response blocks bodies
0 1 6 BROADCAST_TX List<ITransaction> (rlp) src broadcast new transactions
0 1 6 BROADCAST_NEWBLOCK IBlock (rlp) src broadcast new block
0 1 127 UNKNOWN drop message

!! Except table cells with label '(rlp)', messages are encoded / decoded as from top to bottom in each attributes cells on table above.

Handshake Flow

node-a node-b
0 fire connection to node-b receive connection from node-a
1 create record on outbound collection create connection on inbound collection
2 fire request handshake to node-b receive request handshake
if handshake rule passed send node-a response handshake
else no response till node-a get timeout from inbound collection

Connections and Timeout

  • p2p groups 3 collections of connections: inbound, outbound, active.

    • Inbound collection stores incoming connection before handshake process
    • Outbound collection stores outgoing connections before handshake process
    • Active collection stores connections and node info after handshake process succeed.

  • Node time stamp will be refresh on RES_HANDSHAKE, RES_ACTIVE_NODES and so far sync protocols. Connections will be closed if records expired