token ring
	token holding time THT
	token rotation time TRT = num nodes*THT + ring delay
	monitor station
		introduce additional delay
		detect missing token: num nodes*THT + ring delay (max time to see token)

either early token release or delayed token release

wireless
	primary challenge: mediate access to share communication medium
	two problems:
		hidden nodes - nodes are not aware of a collision in the same cell
		exposed node - mangled frames from collisions in overlapping cells
	uses multiple access collision avoidance to fix both problems
	request to send (RTS), clear to send (CTS)
	before sendign data ot make all nodes within range of receiver aware of presence of forthcoming transmission
	in case of exposed node issue, CTS may not be overheard by exposed nodes

switching technologies
circuit switching
	circuit is dedicated comm path between two stations
	requires 3 phases: circuit establishment, data transfer, and circuit termination
	must have intelligence for routing
	once connected, transfer is transparent
	developed for voice traffic (telephony)

packet switching
	break data into small units (datagrams)
	can transfer individual packets through different routes, even if part of the same connection
	each packet treated indepently
	can take any practical route
	may arrive out of order
	may be lost/dropped
	up to receiver to reorder packets
	
packet switches maintain a CAM (forwarding) table to keep track of which MAC addresses are on which ports