Choose the most suitable technology for the DCI (Data Center Interconnect) when Data Centers are geographically not in the same building:

Ethernet Ring Protection Switching (ERPS), defined by the ITU-T G.8032 standard, is specifically designed for resilient ring topologies commonly found in Metropolitan Area Networks (MAN) or carrier networks. This makes it highly suitable for interconnecting geographically separate data centers. ERPS provides rapid convergence times (sub-50ms), ensuring high availability for the Layer 2 DCI link. When combined with the Virtual Router Redundancy Protocol (VRRP), it creates a complete solution that offers both a resilient Layer 2 path and a redundant Layer 3 default gateway for workloads across the data centers.

A. VSX (Virtual Switching Extension) can be used for DCI but has strict low-latency requirements for its Inter-Switch Link (ISL), which may not be met over longer geographical distances.
C. STP (Spanning Tree Protocol) is a legacy protocol with slow convergence times (30-50 seconds), making it unsuitable for modern DCI applications that demand near-instantaneous failover.
D. VSF (Virtual Switching Framework) is a switch stacking technology intended for switches in the same physical location, such as a single rack or wiring closet, and cannot span separate buildings.

1. ArubaOS-CX 10.11 Layer 2 Bridging Guide

Chapter: "Ethernet Ring Protection Switching (ERPS)"

Page 1.

Quote/Paraphrase: "ERPS provides sub-50 ms protection and recovery switching for Ethernet traffic in a ring topology and ensures that there are no loops formed at the Ethernet layer. ERPS is often used in carrier and metro Ethernet networks..." This document confirms ERPS is designed for the exact use case of interconnecting sites over a metro/carrier network with fast failover.

2. ArubaOS-CX 10.11 Virtual Switching Extension (VSX) Guide

Chapter: "VSX deployment considerations"

Section: "VSX split-brain detection".

Quote/Paraphrase: While not giving a hard number

the guide emphasizes the need for a low-latency

high-bandwidth ISL. Industry best practices for stretched clustering technologies like VSX typically recommend a round-trip time (RTT) of less than 10ms

which limits its geographical scope compared to carrier-grade protocols like ERPS.

3. Aruba Design Principles and Methodologies Guide

Chapter 2: "Aruba Campus for Midsize Networks"

Section: "Switching architecture".

Quote/Paraphrase: This guide differentiates VSF and VSX. It describes VSF as a technology for creating a single logical device from a stack of access switches

implying co-location. It positions VSX for the aggregation/core layer for high availability within a site. This context makes VSF clearly unsuitable for DCI between buildings.