Network segmentation is the correct answer because it involves dividing a network into different segments or subnetworks, each acting as a smaller, separate network to enhance security and performance. This is distinct from network security, which is a broad term encompassing all policies and practices to prevent and monitor unauthorized access, misuse, or modification of a computer network. Subnetting merely refers to dividing an IP network into sub-parts for organizational and use purposes, without the specific intent of improving security, and VLANs are just one possible method to create segmented networks.