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(C) Herbert Haas
2005/03/11
History: Switches
Switch = Multiport Bridges with HW acceleration
Full duplex Collision-free Ethernet No CSMA/CD
necessary anymore
Different data rates at the same time supported
Autonegotiation
VLAN splits LAN into several broadcast domains
1
0 Mbit/s
100 Mbit/s
1
00 Mbit/s
1000 Mbit/s
Collision-free
plug & play
scalable Ethernet !
Several vendors built advanced bridges, which are partly or fully implemented in
hardware. The introduced latency could be dramatically lowered and
furthermore other features were introduced, for example full duplex
communication on twisted pair cables, different frame rates on different ports,
special forwarding techniques (e,g, cut through or fragment free), Content
Addressable Memory (CAM) tables, and much more. Of course marketing rules
demand for another designation for this machine: the switch was born.
Suddenly, a collision free plug and play Ethernet was available. Simply use
twisted pair cabling only and enable autonegotiation to automatically determine
the line speed on each port (of course manual configurations would also do). This
way, switched Ethernet become very scalable.
Furthermore, Virtual LANs (VLANs) were invented to split the LAN into several
broadcast domains. VLANs improve security, utilization, and allows for logical
borders between workgroups.