R2511-HP MSR Router Series Interface Configuration Guide(V5)

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Configuring CPOS interfaces
Feature and hardware compatibility
Feature MSR900 MSR93X MSR20-1X MSR20 MSR30 MSR50
MSR10
00
CPOS interface No No No No Yes Yes No
E1-related commands are available for CPOS (E) interface modules. T1-related commands are available
for CPOS (T) interface modules.
Overview
SONET and SDH
Synchronous Optical Network (SONET) adopts optical transmission. It is a synchronous transmission
system defined by the ANSI and is an international standard transmission protocol.
ITU-T Synchronous Digital Hierarchy (SDH) uses synchronous multiplexing and a flexible mapping
structure. It can add or drop low-speed tributary signals to or from SDH signals without a large number
of multiplexing/demultiplexing devices. This reduces signal attenuation and decreases device
investments.
CPOS
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 precise bandwidth division, reduce the number
of low-speed physical interfaces on devices, enhance their aggregation capacity, and improve the
access capacity of leased lines.
The CPOS interface operates at the rate of STM-1 or STM-16.
SDH frame structure
To understand the benefits of CPOS, understand the frame structure of SDH signal STM-N first.
Low-speed tributary signals should distribute in one frame regularly and evenly for the convenience of
adding them to or dropping them from high-speed signals. The ITU-T stipulates that STM-N frames adopt
the structure of rectangle blocks in bytes, as illustrated in Figure 11.