The Fibre Distributed Data Interface (FDDI), ISO/IEC 9314, is intended for use in a high-performance general purpose multi-node network and is designed for efficient operation with a peak data rate of 100 Mbit/s. It uses a Token Ring architecture with optical fibre as the transmission medium. FDDI provides for hundreds of nodes operating over an extent of tens of kilometers. The Physical Layer Protocol (PHY) specifies the upper sublayer of the Physical Layer for the FDDI. As such, it presents the specifications and services provided for conforming FDDI attachment devices. PHY specifies the data encode and decode, framing, and clocking requirements. PHY also specifies the elasticity buffer, smoothing, and repeat filter functions. This part of ISO/IEC 9314 for PHY-2 is an enhancement to the original FDDI standard on PHY (ISO 9314-1).