Distribution Layer
The distribution layer interfaces between the access layer and the core layer to provide many important functions, including:
Aggregating large-scale wiring closet networks
Aggregating Layer 2 broadcast domains and Layer 3 routing boundaries
Providing intelligent switching, routing, and network access policy functions to access the rest of the network
Providing high availability through redundant distribution layer switches to the end-user and equal cost paths to the core
Providing differentiated services to various classes of service applications at the edge of the network