VAST - Protocol

The VAST Protocol 0.1

Message Format

VAST uses a binary protocol, in order to be bandwidth-efficient. All messages begin with a one byte message type id, followed by the message-dependent parameters.

Message Types

Types	Parameters	Expected Reply	Notes
ID To obtain a unique ID	node-id	ID	Reliable
QUERY To find initial acceptor	node	PEER (initial neighbors)	Reliable
HELLO To initiate connection with new neighbor	node, [node-id]*	PEER (missing neighbors)	Reliable
MOVE Position updates to regular neighbors	update
MOVE_B Position updates to boundary neighbors	update	PEER (new neighbors)
PEER Neighbor notification	[node, timestamp]
PAYLOAD Application message sent to a neighbor	size, content		Reliable or unreliable

Notes: Bracket [] indicates a list

* A list of enclosing neighbors' IDs is sent with HELLO.

Message Parameters

Parameter	Contains (size in bytes)	Notes
node-id	Unique-id (4)	System-wide unique ID
pos	X (4), Y (4)	Coordinate of a node (long integers)
addr	IP-address (4), port (2)	IP-address & port a node
aoi	AOI-radius (4)	AOI-radius
node	node-id, pos, addr, aoi	Full information about a node
timestamp	Current time (4)	Timestamp at sender
update	pos, aoi, timestamp	Position update of a node
size	Payload size (4)	Application message size
content	Payload content (variable)	Application message content