Nortel Networks 8000 - Manual (Page 65)

4 POS and CPOS interface configuration
Nortel Secure Router 8000 Series
Configuration -WAN Access
Multiplexing E1/T1 to STM-1
In the SDH multiplexing process stipulated in the G.709 recommendation, you can have more
than one multiplexing route from a valid payload to STM-N.
Figure 4-2 shows the mode of multiplexing E1/T1 to STM-1.
Figure 4-2 Process of multiplexing E1 to STM-1
STM-1
X 1
AUG-1
X 1
AU-4 VC-4
U 3 TUG-3
Multiplexing
Mapping
Aligning
AU-3 VC-3
X 7
’ 7
TUG-2
X 3
C-12: 2.048Mbit/s
TU-12 <— VC-12 C-12
Figure 4-3 Process of multiplexing T1 to STM-1
STM-1
X 1
AUG-1
X 1
AU-4
t x 3
Multiplexing
----- Mapping
...... Aligning
AU-3
VC-4
TUG-3
VC-3
X 7
X 7 C-11: 1.544Mbit/s
TUG-2 TU-11 VC-11 C-11
X 4
In actual applications, different countries and regions may adopt different multiplexing
structure modes. The SR8000 provides the
multiplex mode command on the CPOS interface.
This enables you to select AU-3 or AU-4 multiplexing structure mode.
Calculation of E1/T1 path sequence number
You do not arrange lower order virtual containers in order, because the CPOS interface adopts
the byte interleaved multiplexing mode.
This section considers CPOS E1 using the AU-4 multiplexing route as an example to
introduce the calculation method for the TU sequence number.
When using the AU-4 multiplexing route, the multiplexing structure of E1 is the 3-7-3
structure. Figure 4-2 shows the process of multiplexing E1 to STM-1. The formula for
calculating the TU-12 sequence numbers of di^erent locations in the same VC-4 is as follows:
Sequence number of VC-12 = Number of TUG-3 + (Number of TUG-2 - 1) x 3 + (Number of
TU-12 - 1) x 21
4-4 Nortel Networks Inc. Issue 5.3 (30 March 2009)