Synchronous Ethernet

Achieving High-Quality Frequency Distribution in Ethernet NGNs

By Cisco Systems

Published 2008; Posted February 2009


The world is changing - the more it changes, however, the more the fundamental requirements solidify. In the business world these requirements translate to the customer demands of more bandwidth, more choices, better service, faster speeds, more reliability, and lower prices. Often, but not always, these requirements conflict with the shareholder requirements of higher profitability and thus a lower total cost of ownership (TCO). The direct effect of such an environment on the networking world is a rapid migration to next-generation IP/Multi Protocol Label Switching (MPLS)- based networks (NGNs) with Ethernet as the medium of choice. That said, there is still a widely deployed and extremely lucrative services infrastructure based on the so-called “legacy” technologies of time-division multiplexing (TDM), SONET/SDH, and ATM.


Service Providers (SPs) want to continue servicing existing customers on these “legacy” networks, even as they enhance their access and core networks to handle the huge surge in traffic and the change in traffic patterns. This situation translates to increased importance of applications such as TDM circuit emulation and mobile backhaul as well as interworking between the next-generation IP networks and the existing TDM/SONET/SDH-based infrastructure.


This paper evaluates one of the implications of this business requirement on Ethernet - the need for frequency distribution (usually for synchronization purposes) and the solution(s) that have been devised to address that need (including their advantages, disadvantages, and potential uses).


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