Cisco NCS 4200 Series Configuration Manual page 2

Basic SDH Signal
• One of the two options for the User-Network Interface (UNI) (the customer connection) and formally
Basic SDH Signal
The basic format of an SDH signal allows it to carry many different services in its VC because SDH signal
is bandwidth-flexible. This capability allows the transmission of high-speed packet-switched services, ATM,
contribution video, and distribution video. However, SDH still permits transport and networking at the 2
Mbit/s, 34 Mbit/s, and 140 Mbit/s levels, accommodating the existing digital hierarchy signals. In addition,
SDH supports the transport of signals based on the 1.5 Mbit/s hierarchy.
SDH Hierarchy
SDH Frame Structure
The STM-1 frame is the basic transmission format for SDH. The frame lasts for 125 microseconds, therefore,
there are 8000 frames per second. The STM-1 frame consists of overhead plus a Virtual Container (VC)
capacity.
The SDH frame consists of 270 columns. The first nine columns of each frame make up the Section Overhead,
and the last 261 columns make up the VC capacity. The VC plus the pointers (H1, H2, H3 bytes) are called
the Administrative Unit (AU). Carried within the VC capacity, which has its own frame structure of nine rows
and 261 columns, is the Path Overhead and the Container. The first column is for Path Overhead; it is followed
by the payload container, which can itself carry other containers. VCs can have any phase alignment within
the Administrative Unit, and this alignment is indicated by the Pointer in row four. Within the Section Overhead,
the first three rows are used for the Regenerator Section Overhead, and the last five rows are used for the
Multiplex Section Overhead. The STM frame is transmitted in a byte-serial fashion, row-by-row, and is
1 port OC-48/ 4 port OC-12/OC-3 + 12 port T1/E1 + 4 port T3/E3 CEM Interface Module Configuration Guide, Cisco
IOS XE Fuji 16.7.x (Cisco NCS 4200 Series)
2
the U reference point interface for support of BISDN
Configuring SDH