# suppose 20 nodes with chosen ip addresses
{
init
	node ready; true
	[
	# probe with fresh ip so do nothing
	send_fresh||tran ready; true; y=0; 1.0
	]
	[
	# probe with used ip address (0.5 probability message lost)
	send_used||tran  ready; true; y=0; 0.1
	send_used||tran  send; true; y=0; 0.9
	] 
}
{
	node send; y<=5
	[
	# wait 1 second for meassge to arrive and reply (which may get lost)
	tran ready; y>=1; y=0; 0.1
	tran reply; y>=1; y=0; 0.9
	]
}
{
	node reply; y<=5
	[
	# takes up to 1 second arrive
	recv||tran ready; y>=1; y=0; 1.0
	]
*

# to prevent overlap has assused takes between 0.1 and 0.5 second for message to arrive and for reply to be sent
# this gives overall time limit of les than 2 (the time bwteen sending probes)