|  | 7.5 | Effects of Layer 2 Devices on Data Flow
| 7.5.2 | Bridge segmentation of a collision domain

Ethernet LANs that use a bridge for segmenting the LAN provide more bandwidth per user because there are fewer users on the segments than there are when compared to the entire LAN. The bridge allows only those frames that have destinations outside the segment to pass through. Bridges learn a network’s segmentation by building address tables that contain the physical address of each network device, as well as the port to use to reach the device. Bridges differ from routers because they are Layer 2 devices, and are, therefore, independent of Layer 3 protocols. Bridges pass on data frames, regardless of which Layer 3 protocol is used, and are transparent to the other devices on the network.

Bridges increase the latency (delay) in a network by 10-30%. This latency is due to the decision making that is required of the bridge, or bridges, when transmitting data to the correct segment. A bridge is considered a store-and-forward device because it must receive the entire frame and compute the cyclic redundancy check (CRC) before forwarding can take place. The time it takes to perform these tasks can slow network transmissions, thus causing delay.