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68 Chapter 3
SONET Overhead
SONET provides significant overhead, enabling simpler multiplex-
ing techniques and improved OAM&P operations. The next section
examines overhead in greater detail so as to provide a better under-
standing of why so much time and energy is dedicated to overhead
functions.
Figure 3-11 shows the architecture of the SONET link as defined
by ECSA and ANSI. In this reference, the link architecture is broken
down into three parts:
Section The section is defined as the portion of the link
between two repeater functions or between a repeater and a
piece of line-terminating equipment. Sufficient overhead is
allowed to detect and troubleshoot errors on the link between
these two points (STE).
Line The line overhead provides sufficient information to
detect and troubleshoot problems between two pieces of line-
terminating equipment (LTE).
Path The path overhead provides sufficient overhead to
detect and troubleshoot problems between the end-to-end pieces
of path-terminating equipment (PTE).
Figure 3-11
SONET link
architecture
Section Section Section
Line
Path
