Which network architecture is MOST appropriate for workloads that demand east-west traffic optimization?

Spine-leaf architecture is a two-layer data center network topology designed to overcome the limitations of traditional three-tier architectures. It is specifically optimized for handling east-west (server-to-server) traffic. In this design, every leaf switch connects to every spine switch, creating a high-bandwidth, non-blocking, low-latency fabric. This ensures that traffic between any two servers has a predictable and consistent number of hops (typically two: leaf-to-spine-to-leaf), which is ideal for modern workloads like microservices, big data, and hyper-converged infrastructure that generate significant internal traffic.

B. Hub-and-spoke topology: This model funnels all traffic through a central hub, creating a significant bottleneck for inter-spoke (east-west) communication, making it highly inefficient for this purpose.
C. Flat Layer-2 networks: While simple, large flat Layer-2 networks do not scale well due to issues with broadcast storms and MAC address table limitations, making them unsuitable for demanding workloads.
D. Star topology: Similar to hub-and-spoke, a star topology relies on a central point for all communication, which becomes a performance bottleneck and a single point of failure.

1. HPE Aruba Documentation: In the HPE Aruba Validated Solution Guide - Data Center Networking with EVPN-VXLAN, it states, "The spine-and-leaf architecture is a two-tier network topology built to overcome the performance limitations of the traditional three-tier network architecture. It is designed to provide low latency and high bandwidth for east-west traffic."

Source: HPE Aruba Validated Solution Guide - Data Center Networking with EVPN-VXLAN (Edition 1, March 2021), Page 8, "Spine-and-leaf architecture" section.

2. Academic Publication: The foundational concept for spine-leaf architectures, known as "Fat-Tree," was proposed to address communication patterns within data centers. The paper highlights the need for high aggregate bandwidth for internal traffic. "Our goal is to build a data center network that supports graceful scaling... and allows hosts to communicate at the full bandwidth of their network cards in common communication patterns." This directly addresses the need for optimized east-west traffic.

Source: Al-Fares, M., Loukissas, A., & Vahdat, A. (2008). A scalable, commodity data center network architecture. ACM SIGCOMM Computer Communication Review, 38(4), 63–74. Section 1: Introduction. DOI: https://doi.org/10.1145/1402946.1402967

3. University Courseware: Stanford University's CS244 course on Advanced Topics in Networking discusses data center network topologies, explaining that spine-leaf (or Clos/Fat-Tree) networks are designed to provide high bisection bandwidth, which is critical for handling the all-to-all communication patterns characteristic of east-west traffic in modern data centers.

Source: Stanford University, CS244: Advanced Topics in Networking, Lecture Notes on "Data Center Networking".