Configuring E-Cpos Interfaces; Overview; Sonet; Sdh - HP HSR6800 Configuration Manual

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Configuring E-CPOS interfaces

Synchronous Optical Network (SONET), a synchronous transmission system defined by the ANSI, is an

international standard transmission protocol over fiber-optic. SONET transmission rates form a sequence

of OC- 1 (51.84 Mbps), OC-3 (155 Mbps), OC- 1 2 (622 Mbps), and OC-48 (2.5 Gbps). Because signals

are synchronous, SONET can multiplex signals conveniently.

Synchronous Digital Hierarchy (SDH), defined by the CCITT (today's ITU-T) uses a SONET rate subset. As

SDH uses synchronous multiplexing and allows for flexible mapping, low-speed tributary signals can be

added to or dropped from SDH signals without a large amount of multiplexing/demultiplexing devices.

This reduces signal attenuation and investment in devices.

SDH frame structure

Low-speed tributary signals should distribute in a 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 shown in

Figure 16 STM-N frame structure

STM-N is a rectangle-block frame structure of 9 rows x 270 x N columns, where the N in STM-N equals

the N columns. N takes the value 1, 4, 16, and so on, indicating the number of STM- 1 signals that form

SDH signal.

The STM-N frame structure consists of three parts: the section overhead (SOH), which includes the

regenerator section overhead (RSOH) and the multiplex section overhead (MSOH); the administration

unit pointer (AU-PTR); and payload. AU-PTR is the pointer that indicates the location of the first byte of the

payload in an STM-N frame so that the receiving end can correctly extract the payload.

Figure

16:

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