SDH frame structure
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This section provides detailed information on the locations and functions of various
overhead bytes for each of the following SDH path and line sections:
• Regenerator Section
• Multiplex Section
• Path
Section overhead
The following table identifies the location and function of each regenerator section
overhead byte.
Bytes Function
A1, A2 Frame alignment A1 = 1111 0110 ; A2 = 0010 1000 ; These
fixed-value bytes are used for synchronization.
B1 BIP-8 parity test
Regenerator section error monitoring; BIP-8 :
Computed over all bits of the previous frame after scrambling; B1 is
placed into the SOH before scrambling;
BIP-X: (Bit Interleaved Parity X bits) Even parity, X-bit code;
first bit of code = even parity over first bit of all X-bit sequences;
B2 Multiplex section error monitoring; BIP-24 :
B2 is computed over all bits of the previous STM-1 frame except for
row 1 to 3 of the SOH (RSOH); B2 is computed after and placed
before scrambling;
Z0 Spare bytes
D1-D3(=
DCC
R
)D4-
D12 (= DCC
M
)
Data Communication Channel (network management information
exchange)
E1 Orderwire channel
E2 Orderwire channel
F1 User channel
K1, K2 Automatic protection switch
K2 MS-AIS/RDI indicator
S1 Synchronization Status Message
M1 REI (Remote Error Indication) byte
NU National Usage
An SDH overview
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365-312-801R7.2
Issue 3, May 2007
Alcatel-Lucent - Proprietary
See notice on first page
A-9
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