363-206-295
A SONET Overview
A-16
Issue 1
December 1997
Concatenated Mode
1
For services requiring multiples of the STS-1 rate, STS-1 path payloads may be
shared to create a single broadband payload called a concatenated STS-
Nc
(OC-
Nc). STS-1 signals are mapped into an STS-Nc SPE and transported as a
concatenated STS-
Nc signal. This STS-Nc signal can be carried by an STS-N or
OC-
N (or higher level) line signal.
The STS-
N signal is multiplexed, switched, and transported through the network
as a single entity. A concatenation indicator, used to show that the STS-1s of the
STS-
Nc signal are linked together, is contained in the STS-1 payload pointer of all
but the first STS-1. The line and section overhead is sent on the first STS-1 and
the payload pointer for the first STS-1 is applied to all STS-1 signals in the
concatenated signal.
Figure A-10 shows an example of an STS-3c SPE. It consists of 3 x 87 columns
and 9 rows of bytes. The order of transmission is row by row, from left to right.
Figure A-10. STS-3c Concatenated Payload
J1
B3
C2
G1
F2
H4
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
3
H1
C
C
H2
C
C
H3
H3
H3
PayLoad Pointer
Transport Overhead
3 x 87 Columns STS-3c Payload
STS-3c POH
STS-1 #
Time
Path OverHead Byte
PayLoad Byte
Concatenation Byte
Pointer Byte
Stuff Byte
C
H1,H2
H3
125
µ
s
