Cisco ASR 900 Series Configuration Manual page 109

Configuring SDH
SDH Frame Structure
scrambled immediately prior to transmission to ensure adequate clock timing content for downstream
regenerators.
Figure 6: STM1 Frame Structure
Figure 7: STM1 Section Overhead
VC
SDH supports a concept called VC. Through the use of pointers and offset values, VCs can be carried in the
SDH payload as independent data packages. VCs are used to transport lower-speed tributary signals. Note
that it can start (indicated by the J1 path overhead byte) at any point within the STM-1 frame. The start location
of the J1 byte is indicated by the pointer byte values. VCs can also be concatenated to provide more capacity
in a flexible fashion.
1 port OC48/ 4 port OC12/OC3 + 12 port T1/E1 + 4 port T3/E3 CEM Interface Module Configuration Guide, Cisco IOS
XE Fuji 16.7.x (Cisco ASR 900 Series)
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