Synchronous Ethernet – A RAD White Paper

同步以太网技术白皮书 As more and more traffic is being delivered in Ethernet format, carriers are realizing the advantages to converging on a pure Ethernet infrastructure, but are not able to do so with Ethernet as presently defined. New ITU-T Recommendations, such as Y.1731 for Ethernet OAM and G.8031 for Ethernet protection switching, provi de features essential for operational maintenance of Ethernet networks. Recently proposed mechanisms for configuring point-to-point connections in Ethernet networks close another gap between Ethernet and SONET/SDH networks. The final difference between conventional TDM-based networks and Ethernet is that the former also transport frequency information, needed for some applications, while Ethernet does not. Numerous methods have been suggested for augmenting Ethernet to distribute frequency and/or timing information, such as IEEE 1588, IETF’s NTP, and methods developed for use of TDM pseudowires. In this article I will talk another method for transport of synchronization over Ethernet networks, for those applications that need it. This method locks the timing of the Ethernet physical layer, much the same way that SONET/SDH does. This enables simple recovery of the physical layer timing, which can be used directly by locking downstream networks and applications, or indirectly by using the physical layer timing as a common reference. de features essential for operational maintenance of Ethernet networks. Recently proposed mechanisms for configuring point-to-point connections in Ethernet networks close another gap between Ethernet and SONET/SDH networks. The final difference between conventional TDM-based networks and Ethernet is that the former also transport frequency information, needed for some applications, while Ethernet does not. Numerous methods have been suggested for augmenting Ethernet to distribute frequency and/or timing information, such as IEEE 1588, IETF’s NTP, and methods developed for use of TDM pseudowires. In this article I will talk another method for transport of synchronization over Ethernet networks, for those applications that need it. This method locks the timing of the Ethernet physical layer, much the same way that SONET/SDH does. This enables simple recovery of the physical layer timing, which can be used directly by locking downstream networks and applications, or indirectly by using the physical layer timing as a common reference.