The three message primary test sequence confirms the existence of a fully functional bi directional path between the two access points of {HEAD ~ a node} redundantly connected to {TAIL ~ a network} 
redundantly connected to
The three message primary test sequence confirms the existence of a fully functional bi directional path between the two access points of { HEAD ~ a node } redundantly connected to { TAIL ~ a network }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL