Cuda 12000 IP Access Switch CLI-based Administration Guide
Packet Over SONET (POS) Interface Administration 129
Section Layer Administration
The primary roles of the section layer include synchronization and timing of
the SONET transmission, and passing the electrical STS-n frame format to the
photonic layer where it is then converted to an optical signal and transported
to the adjacent device.
Section layer administration involves viewing the current status of the
configuration and modifying the configuration of the section layer
parameters for a selected POS interface. You can configure the following
POS section layer parameters:

Loopback Configuration

Loopback configuration on a POS interface allows you to test interface
connectivity and connection to a remote device. By default, loopback is not
configured. The system supports the following loopback configuration:
■Line — Configures the POS interface to loop-back data to the originating
device. While configured in this mode, the interface loops back and
retransmits incoming data without actually receiving it.
■Internal — Configures the POS interface to loop-back data to itself.
While configured in this mode, the interface loops-back outgoing data to
the receiver without actually transmitting it.
To configure loopback testing on a selected POS interface, perform the
following tasks in interface pos <c/s/i> mode:
Task Command
1. Enable loopback testing. loop {line | internal}
2. Disable loopback testing. no loop