The ____ layer is often called a high-speed backbone.

• A. Access
• B. Distribution
• C. Physical
• D. Core

Answer: (D)

In network design, the layer that serves as a high-speed backbone is the core layer. Its job is to interconnect the major parts of the network and move large amounts of traffic quickly and reliably, with minimal processing that could slow things down. It uses high-capacity links and devices to keep latency low and to provide redundancy, so data can flow across the network even if some paths fail. The access layer is where end-user devices connect to the network, the distribution layer aggregates those connections and enforces policies and routing between access blocks, and the physical layer refers to the actual transmission of raw bits. Because the core is all about fast, scalable transport between major network segments, it’s the backbone.