ABSTRACT: Information system users expect a high degree of service availability. At the network level, this is achieved by employing fault-tolerant architectures, redundancy for critical network elements and their subsystems, and efficient fault detection and recovery mechanisms.

For traditional telecommunications equipment with a design service life objective of at least 25 years, generic requirements for these network elements (switch, transport, cross-connect, etc.) are detailed in GR-78 and GR-357. However, as communications, computer, and consumer industries converge, equipment from newly emerging manufacturers do not conform to key reliability and technology requirements of GR-78 and GR-357 necessary to achieve long service life. Instead, equipment design and manufacturing processes result in equipment with service life objectives ranging from no defined value to, at most five years; and it for this category of equipment that this NEBS (Network Equipment-Building System)document is published. It is intended to facilitate rapid deployment so as to exploit market opportunities as they arise, and to allow network operators the necessary flexibility to mix and match different equipment categories (long-life and short-life) as needed to optimize network solutions in terms of performance and cost.