Implementing Synchronous Ethernet in Telecommunication Systems

Network infrastructures are gradually migrating from time-division multiplexing (TDM) based onto packet-based architectures. In spite of this convergence, there are a significant number of synchronous applications that require accurate timing to be distributed over the packet networks. Examples of precision timing sensitive applications that need the transport of synchronization over packet networks include interconnection and transport of TDM services over packet networks (TDM switches, TDM PBXs, voice, video-conferencing and broadband video), and connections to 2G, 3G, and 4G wireless base stations. TDM networks, unlike packet networks (e.g., Ethernet, IP, MPLS), have timing transfer inherently built into them. Native Ethernet (IEEE 802.3) is inherently asynchronous and was not designed with timing transfer in mind. Synchronous Ethernet (Sync-E), defined by the ITU-T, has emerged as a powerful, yet simple technology, for accurate timing transfer over Ethernet networks using quotedblleft TDM-likequotedblright (precisely, SDH/SONET) timing techniques. This discussion explains what Sync-E is, followed by a detailed discussion on which flavors of Ethernet can support Sync-E and which cannot. The discussion includes how Sync-E can be implemented in the popular Ethernet versions. We then describe example Sync-E node timing architectures, and some network timing applications and related issues.