gs to customers. In addition to many of the capabilities described earlier, there would also be a need to support synchronization, both frequency and time. The focus of Synchronous Ethernet is likely to be where the deployment of Ethernet is most prevalent-namely, toward access and aggregation. The essence of Synchronous Ethernet is that it locks the Ethernet physical layer (in IEEE terms the PHY; in ITU-T terms, the ETY) to a reference clock and distributes it to down- stream elements. The introduction of Synchronous Ethernet requires some additional capa- bilities to be added to Ethernet hardware-namely, the ability to insert and extract the appropriate clock rates into and from the Ethernet PHY and the ability to add appropriate status messaging (containing reference traceability information). A Synchronous Ethernet solution would be embedded within the transport medium and managed while being secure and free from the fundamental issues that impact synchro- nization recovery in packet-based solutions. It also permits interworking with existing Eth- ernet architectures and should not create any significant interworking problems that would affect existing Ethernet standards or interfaces-that is, traffic would continue to run at the MAC frame level and pass from a Synchronous Ethernet to a native Ethernet domain. There has been significant progress in the development of Synchronous Ethernet standards. The high-level concepts of Synchronous Ethernet and the Synchronous Ethernet Equipment Clock were published in ITU-T recommendations G.8261 (ITU-T, 2006a) and G.8262 (ITU-T, 2007). It is anticipated at the time of writing that G.8261 will be updated in 2008 to include information regarding Synchronous Ethernet messaging. Next Generation Ethernet Transmission The transport networks of the telecommunications industry assign bitrates in steps of 4 (e.g., the SDH hierarchy increases from STM-1 through STM-4, STM-16, and STM-64 up to STM-256, covering the range from 155 Mbit/s to 40 Gbit/s). At the same time, the Ethern