Ethernet Switches

Ethernet Switches :

• layer 2 (frame) forwarding, filtering using LAN addresses .
  
• Switching: A-to-B and A'-to-B' simultaneously, no collisions
  
• large number of interfaces
  
• often: individual hosts, star-connected into switch(Ethernet, but no collisions!)
  
• cut-through switching: frame forwarded from input to output port without awaiting for assembly of entire frame slight reduction in latency.
  
• -combination of shared/dedicated, 10/100/1000 Mbps interfaces.

An Ethernet Switch is a LAN interconnection device which operates at the data link layer (layer 2) of the OSI reference model. A switch is fundamentally similar to a bridge, but usually supports a larger number of connected LAN segments and has a richer management capability.

Modern LANs have increasingly replaced the shared media with a switched media, by installing Ethernet switches and bridges in place of hubs and repeaters. These logically partition the traffic to travel only over the network segments on the path between the source and the destination. This reduces the wastage of bandwidth which results from sending the packet to parts of the network which do not need to receive the data. There are also benefits from improved security (users are less able to tap-in into other user's data), better management (the ability to control who receives what information (i.e. Virtual LANs) and to limit the impact of network problems), and the ability to operate some links in full duplex (rather than half duplex required for shared access).