ually occurs when there is a physical need to do SO. An excellent example is a college or business campus: there might be core switches (possibly in a central location), distribution switches in each building, and access switches close to the users in each building. The specifics depend on the physical layout of the campus. Figure 35-8 shows a textbook three-tiered cor- porate network. At the bottom of the drawing, users, printers, IP phones, and wireless access points (APs) are connected to the access-layer switches. The access-layer switches are con- nected to the distribution-layer switches in the middle row. The distribution switches connect to the top two switches, which are the core of the network. The Internet and the server farm are both connected to the core in this example. Collapsed core-no distribution Collapsed-core networks are very common. I work a lot in Manhattan, where sky- scrapers are the norm. Office space in skyscrapers is usually allocated on a floor-by- floor basis. Wiring is usually run from points on the floor to a central location on the same floor. Floors are usually interconnected with conduits that run between floors. When a company occupies multiple floors, the wiring of each floor lends itself to a collapsed-core design, because there are limited wiring possibilities between floors. Because the amount of space on each floor is limited, there is typically little need for more than two physical network layers. With the core switches on one floor and access switches on the remaining floors, the access switches can act as distribution-layer Network Designs Internet Server farm 00000 Users, printers, etc. Figure 35-8. Typical three-tiered corporate network switches as well. Port density is usually not an issue, as each floor does not occupy much physical space. From a logical standpoint, the distribution layer may be collapsed into the core as well. You may not even need a logical distribution layer at all. Again, each environment is different. Server Farms-Where Do They Belong? Do serv