[1] The hierarchical design model divides enterprise networks into three layers: core, distribution, and access.
The traditional focus at the access layer is minimizing "cost-per-port": the amount of investment the enterprise must make for each provisioned Ethernet port.
Distribution layer devices also often manage individual branch-office WAN connections.
The core layer is the backbone of a network, where the internet(internetwork) gateways are located.
Core switches and routers are usually the most powerful, in terms of raw forwarding power, in the enterprise; core network devices manage the highest-speed connections, such as 10 Gigabit Ethernet or 100 Gigabit Ethernet.