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Configuring CPOS interfaces
Overview
The low-speed tributary signals multiplexed to form an SDH signal are called channels. The channelized
POS (CPOS) interface makes full use of SDH to provide the following benefits:
• Provides precise bandwidth division.
• Reduces the number of low-speed physical interfaces on devices.
• Enhances aggregation capacity.
• Improves the access capacity of leased lines.
The device supports the CPOS interfaces in Table 1.
Table 1 CPOS interfaces
Interface t
CPOS E1 63 E1 channels (E1 channel configurable).
CPOS T1 84 T1 channels (T1 channel configurable).
Overhead bytes
SDH provides layered precise monitoring and management.
SDH monitoring functions are implemented using overhead bytes. SDH provides monitoring at section
and channel levels.
• Sections are subdivided into regenerator and multiplex sections.
• Channels are subdivided into higher-order and lower-order paths.
SDH provides a variety of overhead bytes, but only those involved in CPOS configuration are discussed
in this section.
SOH
The section overhead (SOH) is further classified into the regenerator section overhead (RSOH) and the
multiplex section overhead (MSOH).
The J0 regenerator section trace byte is included in RSOH to repeatedly send the section access point
identifier. The receiver uses this identifier to make sure it is in continuous connection with the sender. This
byte can be any character in the network of the same carrier. If the networks of two carriers are involved,
the sending and receiving devices at network borders must use the same J0 byte. With the J0 byte,
carriers can detect and troubleshoot faults in advance or use less time to recover networks.
POH
The payload of an STM-N frame includes the path overhead (POH), which monitors low-speed tributary
signals.
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