Calculation of E1/T1 Path Sequence Number

CPOS interfaces adopt the multiplexing mode of byte interleave, so the lower-order VCs in a higher-order VC are not arranged in sequence. To facilitate user configuration, the following takes E1 in CPOS adopting AU-4 multiplexing path as an example to introduce the method of calculating the TU number.

The multiplexing process in Figure 16-6 shows that the 2 Mbit/s multiplexing structure is 3-7-3 when the AU-4 multiplexing path is adopted. The following formula shows how to calculate the numbers of TU-12s that are located in different positions in a VC-4:

TU-12 number = TUG-3 number + (TUG-2 number – 1) x 3 + (TU-12 number – 1) x 21

In a VC-4, all TUG-3s are numbered the same; all TUG-2s are numbered the same; the difference between two TU-12 numbers is 1. These two TU-12s are adjacent.

• The numbers listed in the preceding formula stand for the positions in a VC-4 frame.

• The TUG-3 number ranges from 1 to 3; the TUG-2 number ranges from 1 to 7; the TU-12 number ranges from 1 to 3.

• The TU-12 number indicates which one of the 63 TU-12s is in the VC-4 frame according to the sequence and also indicates the E1 channel number.

Figure 16-6 Sequence of arrangement of TUG-3, TUG-2, and TU-12 in VC-4

When the AU-3 multiplexing path is adopted, the calculation of the TU-12 number can be deduced in a similar manner.

When 63 E1 channels or 84 T1 channels are configured on a CPOS interface, these channels can be directly numbered from 1 to 63 or 1 to 84. If a router of Huawei is connected to a channelized STM-1 interface of a non-Huawei router, note differences in channel numbers.