LAN topologies:
	bus
	ring
	tree
	star
	multilevel hub topologies

switches divide collision domains
routers divide broadcast domains

802 standards
802.3
	bus/tree/star tops
	csma/cd
802.5
	token ring
802.11
	wireless

lots of encapsulation
tcp,ip,link,mac
802.3 frame format (number of octets):
	preamble: 7
	sfd: 1 (start of frame delimiter)
	destination address: 2 or 6
	source address: 2 or 6
	length: 2
	data unit, pad: 46-1500
	fcs: 4

2 parts to MAC, 3 bytes of vendor (organizationally unique identifier aka OUI), 3 bytes of custom
exponential backoff for collisions
# of attempts	delay
1		0 or 51.2us
2		0, 51.2, 102.4, 153.6
......

token ring
	token required to transmit, passed around ring

MAN (metropolitan)