Utility Communication Networks and Services by Carlos Samitier

Author:Carlos Samitier
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Synchronous Ethernet locks the timing of the Ethernet physical layer much in the same way as SONET/SDH. The physical layer transmitter clock is derived from a high quality frequency reference traceable to a primary reference clock instead of the ±100 ppm crystal clock of the Ethernet node. The receiver, at the other end of the link, locks to the physical layer clock of the received signal. Then, in TDM fashion, this receiver locks the transmission clocks of its other ports to this frequency reference. In this manner, by feeding one network element in the Ethernet network with a primary reference clock, and employing appropriate timing recovery in the Ethernet physical circuitry, we can set up a frequency-synchronized network (but not necessarily time-synchronized).

Implementing a Synchronous Ethernet solves many of the problems of legacy protection over packet networks and TDM pseudowire emulation described previously, and simplifies accurate time stamping issues of this section. However, it requires that all switches involved in the network be equipped with adequate oscillators and timing recovery mechanisms.

Multi-casting and data flow filtering

Multi-casting is the capability of simultaneous transmission of a message to multiple destinations and is essential to a great number of PSN-based protection applications. GOOSE messages and time-stamped measurements often require to be sent as multicast.

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