virtual circuit switching
port and virtual circuit identifier are assigned when a packet comes in, output port and output VCI are also assigned
a frame travelling through the network can have several VCIs along the way, they only have local significance

repeaters: regenerates physical signal
bridges: separate collision domains (simple switch), no info kept about where MACs can be found, flood a packet to all attached networks
some bridges have the ability to learn where MACs reside and remember it for future reference
3 modes for learning bridges/switches:
	filtering: source and dest are known to be on same segment, drop frame
	forwarding: source and dest are known to be on different segments, pass frame to correct segment
	flooding: dest port is unknown, forward frame out all segments except the one it came in on