Purpose: The purpose of this document is to provide general and specific design and implementation guidelines for the use of IEEE 802.3 (ISO/IEC 8802-3) compliant Ethernet Local Area Networks (ELAN) in the commercial avionics environment. Such use is not intended to be limited to any particular middle or upper communication layer profile even though the Physical Layer and Medium Access Control Sublayers are specifically designed to comply with the OSI Basic Reference Model and associated protocols. Furthermore, it is the intent of this document to modify the existing applicable standards as little as possible so as to enable maximal utilization of components (hardware and/or software) and equipment already in existence or under development.