Conversation so far:
What are scalable data center network architectures?
DCNs need to be scalable and efficient to connect tens or even hundreds of thousands of servers to handle the growing demands of Cloud computing.
What are some examples of scalable data center network architectures?
1 Three-tier DCN 2 Fat tree DCN 3 DCell
Describe the characteristics of FAT tree topology.
In a fat tree, branches nearer the top of the hierarchy are fatter (thicker) than branches further down the hierarchy. In a telecommunications network, the branches are data links; the varied thickness (bandwidth) of the data links allows for more efficient and technology-specific use.

Question: What routes can be taken by an upstream packet?
Self-contained rewrite: What routes can be taken by an upstream packet?