Emerging Applications of Synchronous Ethernet in Telecommunication Networks

Abstract

The current rising demand for broadband services calls for network technologies that deliver significantly lower cost-per-bit than traditional TDM networks. Ethernet, in particular carrier-grade Ethernet technologies (as defined in the Metro Ethernet Forum (MEF) and ITU-T standards), is now being deployed by Telecom service providers from the core to the access. However, given that many of these broadband services require precise synchronization for efficient operation, the distribution of timing signals over Ethernet has become just as critical as the data that it carries. Synchronous Ethernet (Sync-E), defined in a suite of ITU-T Recommendations, provides a method of distributing frequency over Ethernet links. ITU-T Recommendations G.8261, G.8262, G.8264 (which define Sync-E) indicate that synchronization can be achieved over Ethernet links by synchronizing the bit clock of the physical layer as is currently done on SONET/SDH links. In this paper, we describe applications which harness one of the main attributes of Sync-E, which is essentially native Ethernet equipped with point-to-point distribution of timing signals. By enabling point-to-point distribution of timing signals from an accurate timing reference source, Sync-E aims to bring carrier grade telecom quality clocks to packet networks. The paper also discusses some emerging applications of Sync-E, particularly, those applications that can exploit both the high data carrying capacity and clock distribution attributes of Sync-E.