Cisco ASR 900 Series Configuration Guide

• Multiplexing – This process is used when multiple lower-order path layer signals are adapted into a
higher-order path signal, or when the higher-order path signals are adapted into a Multiplex Section.
• Stuffing – As the tributary signals are multiplexed and aligned, some spare capacity is designed into
the SDH frame to provide enough space for all the various tributary rates. Therefore, at certain points
in the multiplexing hierarchy, this space capacity is filled with “fixed stuffing” bits that carry no
information, but are required to fill up the particular frame.
Modes of SDH
A Synchronous Transport Module (STM) signal is the Synchronous Digital Hierarchy (SDH) equivalent of
the SONET STS. In this document, STM term refers to both path widths and optical line rates. The paths
within an STM signals are called administrative units (AUs).
An AU is the information structure that provides adaptation between the higher-order path layer and the
multiplex section layer. It consists of an information payload (the higher-order VC) and an AU pointer, which
indicates the offset of the payload frame start relative to the multiplex section frame start.
The AU-3 pointer is composed of 3 bytes; the AU-4 pointer is composed of 9 bytes.
The payload of the STM-1 frame consists of one AU-4 unit or three AU-3 units.
Augment Mapping
An administrative unit group (AUG) consists of one or more administrative units occupying fixed, defined
positions in an STM payload. Augment mapping is supported at STM1 level.The following types of augment
mapping are supported:
•
Augment Mapping AU-4
This is the default augment mapping mode.Note
•
Augment Mapping AU-3
•
Mixed (AU-3 and AU-4) Augment Mapping
The supported modes of SDH are:
•
AU-4-16c (VC4-16c)
•
AU-4-4c (VC4-4c)
•
AU-4 (VC4)
• AU-4 — TUG-3 — VC-3 — DS3
• AU-4 — TUG-3 — VC-3 — E3
• AU-4 — TUG-3 — TUG-2 — VC-11 — T1
• AU-4 — TUG-3 — TUG-2 — VC-12 — E1
• AU-4 — TUG-3 — TUG-2 — VC-11
• AU-4 — TUG-3 — TUG-2 — VC-12
• AU-3 — VC-3 — DS3
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)
76
Configuring SDH on 1-Port OC-192/STM-64 or 8-Port OC-3/12/48/STM-1/-4/-16 Module
Modes of SDH

Cisco ASR 900 Series Specifications

General

Brand	Cisco
Model	ASR 900 Series
Category	Network Router
Language	English