Networks grow like untreated vegetation in the hidden corner of a backyard — it is not unusual in data centers to find many layers whose sole purpose is to support other network layers.
Consider the fact that half of the network ports in the three-tier networks we all grew to know connect network devices with other network devices, while the other half connect servers to the network. There has to be a way to improve that ratio. IT has woken up and realized the need to reduce the cost of networking gear, and in turn, spend less time (and money) running the network. Put simply, the way to get there is to flatten the data center network.