H3C Technologies H3C SR8800 - Manual (Page 51)

44
Figure 15 Process of multiplexing four STM-1 frames into an STM-4 frame
The recipient will demultiplex a received STM-4 frame into four STM-1 frames. During the multiplexing
process, the A1, A2, J0, Z0, B1, E1, F1, D1, D2, and D3 fields in the RSOH of the first frame are
multiplexed into the STM-4 frame while those of the rest three frames are treated as invalid. The other
fields of each frame are multiplexed into the STM-4 frame separately.
Figure 16 shows how an STM-16 frame in the SDH frame format is demultiplexed.
Figure 16 The process of demultiplexing an STM-16 frame in the SDH frame format
Rate hierarchy of SONET/SDH
SDH frames at different rates are identified in the form of STM-N (N equals 1, 4, 16, 64, and so on,
indicating that the frame is formed through multiplexing and interleaving N STM-1 frames). SONET
frames at different rates are identified in the form of STS-N (N equals 1, 3, 12, 48, and so on, indicating
that the frame is formed through multiplexing and interleaving N STS-1 frames. The following table lists
the rate hierarchies of SONET and SDH.
Table 1 Rate hierarchy of SONET/SDH
SONET SDH Rate
STS-1 N/A 51.840 Mbps
D
Section overhead
payload AU pointer
Section overhead
C
Section overhead
payload AU pointer
Section overhead
B
Section overhead
payload
Section overhead
AU pointer
A
Section overhead
payload AU pointer
Section overhead
P
O
H
A B C D A B C D