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|
4.3 | |
Switch Operation | |
| 4.3.5 | |
LAN segmentation using bridging |
| Ethernet LANs that use a bridge to
segment the LAN provide more bandwidth per user because there are fewer
users on each segment. In contrast, LANs that do not use bridges for
segmentation provide less bandwidth per user because there are more
users on a non-segmented LAN.
Bridges segment a network by building address tables that contain the address of each network
device and which segment to use to reach that device.
Bridges increase the latency in a network
by 10 to 30 percent. This latency is due to the decision-making required
of the bridge or bridges in transmitting data. A bridge is considered a
store-and-forward device because it must examine the destination address
field and calculate the CRC in the frame check sequence field, before
forwarding the frame. If the
destination port is busy, the bridge can temporarily store the frame
until the port is available. The time it takes to perform these tasks
slows the network transmissions causing increased latency.
|
Bridges are
Layer 2 devices that forward data frames based on MAC
addresses of the frame. In addition, bridges are transparent to the other devices on
the network. 
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