Aion P2p Specifications

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