History: bridges – HP 180 Degree Turn User Manual

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History: Bridges

Store and forwarding according destination MAC

address
Separated collision domains
Improved network performance
Still one broadcast domain

Three collision

domains in this

example !

Bridges were invented for performance reasons. It seemed to be impractical that
each additional station reduces the average per-station bandwidth by 1/n. On the
other hand the benefit of sharing a medium for communication should be still
maintained (which was expressed by Metcalfe's law).
Bridges are store and forwarding devices (introducing significant delay) that can
filter traffic based on the destination MAC addresses to avoid unnecessary
flooding of frames to certain segments. Thus, bridges segment the LAN into
several collision domains. Broadcasts are still forwarded to allow layer 3
connectivity (ARP etc), so the bridged network is still a single broadcast domain.