The Top-of-Rack (ToR) cabling layout places an access switch directly inside each rack. Each server in
that rack only requires a short patch cable to connect to the switch, and only one or two uplinks per
rack connect to aggregation switches. This greatly reduces the number of long horizontal cables
across the data hall.
In contrast, an End-of-Row (EoR) design centralizes switches at the row end, requiring long horizontal
cables from each server to the row cabinet. This can lead to thousands of extra copper or fiber runs
in large deployments.
ANSI/TIA-942 and Cisco Design Guides emphasize that ToR is the best solution for minimizing cable
bulk, improving airflow, and reducing cost in hyperscale or dense rack environments.
Thus, if the explicit design goal is to minimize cable quantity, ToR design is superior.
Reference: ANSI/TIA-942-B §8.2 (Cable Topologies: ToR, MoR, EoR), Cisco Data Center Access Layer
Design Guide.
