The distribution layer is one of the three layers in the hierarchical internetworking model. The distribution layer stands between the access layer and the core layer. The distribution layer plays a variety of roles. For example, inter-VLAN routing may occur at this layer. So might the application of ACLs, security policies, or QoS prioritization.
Because the distribution layer focuses on relatively complex traffic shaping, filtering, and processing issues, this layer might be provisioned by multilayer switches or even routers. By focusing complex policy implementation at the distribution layer, this frees the core layer for high speed, high volume, link-level communications.