The Synchronous Ethernet (SyncE) MIB is defined
for monitoring network synchronization based on
ITU-T G.781 clock selection.

Synchronous Ethernet (SyncE) is a standard defined
for delivering timing to the remote NEs through a 
Packet Network.   SyncE is well defined by ITU-T
which included G.8261, G.8262, G.8264 and G.781.
It leverages the PHY layer of Ethernet to transmit
frequency to the remote sites.  Its functionality
and accuracy mimics that of the SONET/SDH network
because of its physical layer characteristic.
In order to allow best clock source traceabiliy,
correctly define the timing source and helps
preventing timing loop, Synchronization Status
Message is required for SyncE.  This is similar
to SONET/SDH.  However, since SONET/SDH use 4 bits
from the two S bytes in the SONET/SDH overhead
frame for such message, Ethernet relies on a
different channel called ESMC (Ethernet
Synchronization Messaging Channel) which is based
on IEEE 802.3 Organization Specific Slow Protocol.

Glossary:
AIS: Alarm Indication Signal
ATM: Asynchronous Transfer Mode
EEC: Ethernet Equipment Clock
ESMC: Ethernet Synchronization Messaging Channel
QL: Quality Level
SASE: Stand Alone Synchronization Equipment
SSM: Synchronization Status Messaging