Sonet Hierarchy; Line; Path - Cisco ASR 900 Series Configuration Manual

SONET Hierarchy

SONET Hierarchy

Figure 1: A SONET Link
Each level of the SONET hierarchy terminates its corresponding fields in the SONET payload, as follows:
Section
A section is a single fiber run that can be terminated by a network element (Line or Path) or an optical
regenerator.
The main function of the section layer is to properly format the SONET frames, and to convert the electrical
signals to optical signals. Section Terminating Equipment (STE) can originate, access, modify, or terminate
the section header overhead.

Line

Line-Terminating Equipment (LTE) originates or terminates one or more sections of a line signal. The LTE
does the synchronization and multiplexing of information on SONET frames. Multiple lower-level SONET
signals can be mixed together to form higher-level SONET signals. An Add/Drop Multiplexer (ADM) is an
example of LTE.

Path

Path-Terminating Equipment (PTE) interfaces non-SONET equipment to the SONET network. At this layer,
the payload is mapped and demapped into the SONET frame. For example, an STS PTE can assemble 25
1.544 Mbps DS1 signals and insert path overhead to form an STS-1 signal.
This layer is concerned with end-to-end transport of data.
1-Port OC-192 or 8-Port Low Rate CEM Interface Module Configuration Guide, Cisco IOS XE Everest 16.7.x
(Cisco ASR 900 Series)
22
Configuring SONET