|  | 1.3 | LAN Design
| 1.3.7 | Developing Layer 2 LAN topology
The purposes of Layer 2 devices in the network are to provide flow control, error detection and correction, and to reduce congestion in the network. The two most common Layer 2 devices (other than the NIC, which every host on the network has to have) are bridges and LAN switches. This section will concentrate on the implementation of LAN switching at Layer 2. Collisions and collision domain size are two factors that will negatively affect the performance of a network. By using LAN switching we can create microsegmentation of the network thus effectively eliminating collisions and reducing the size of collision domains. Another important characteristic of the LAN switch is how it can allocate bandwidth on a per port basis thus allowing more bandwidth to vertical cabling, uplinks and servers.