Page 84 - Optical Switching And Networking Handbook
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04_200023_CH03/Batesx 1/17/01 9:42 AM Page 69
SONET 69
Overhead
The overhead is shown in Figure 3-12. This overhead contains 9
bytes of information that is accessed, generated, and processed by
the section-terminating equipment. It supports functions such as
Performance monitoring
A local orderwire
Data communications channels for OAM&P messages
Framing information
Line Overhead
The line overhead used between two pieces of LTE provides for
OAM&P functions.This is more extensive than the section overhead.
Figure 3-12 A A J /Z J 1
1 2 0 0
SONET overhead
B E F
1 1 1 B 3
D D D C
1 2 3 2
H H H G
1 2 3 1
B K K F
2 1 2 2
D D D H 4
4 5 6
D D 8 D 9 Z
7 3
D D D Z 4
10 11 12
S Z E Z 5
1 2 2
