This white paper reviews the more common technologies used in the industry today to achieve carrier-class network high availability. It identifies the strengths and weakness of different alternatives and goes on to identify challenges with today’s solution approaches and how these can be resolved using an enhanced approach called Layer 2 High Availability (L2HA). The principles employed in L2HA can provide significant advantages over current practices. This document is intended for system architects and engineers who are considering how to build a reliable network infrastructure within an ATCA-based platform for network element applications.