Page 1149 - 5G Basics - Core Network Aspects

Transport aspects 2

15.8.2 ODU OH definition

15.8.2.1 ODU path monitoring (PM) overhead
One field of an ODU path monitoring overhead (PM) is defined in row 3, columns 10 to 12 to support path
monitoring and one additional bit of path monitoring is defined in row 2, column 3, bit 7.

The ODUk contains one instance of ODU PM overhead. The ODUCn contains n instances of the ODU PM
overhead, numbered 1 to n (PM #1 to PM #n).

The PM and PM #1 field contains the following subfields (see Figure 15-18):
 trail trace identifier (TTI);
 bit interleaved parity (BIP-8);

 backward defect indication (BDI);
 backward error indication (BEI);
 status bits indicating the presence of a maintenance signal (STAT).
The PM #2 to #n fields contains the following subfields (see Figure 15-18):

 bit interleaved parity (BIP-8)
 backward error indication (BEI)
 reserved (RES).

The PM&TCM field contains the following PM subfield (see Figure 15-18):
 path delay measurement (DMp).
For the case of ODUk, the content of the PM field, except the STAT subfield, will be undefined (pattern will
be all-1s, 0110 0110 or 0101 0101 repeating) during the presence of a maintenance signal (e.g., ODU-AIS,
ODU-OCI, ODU-LCK). The content of the PM&TCM field will be undefined (pattern will be all-1s, 0110 0110
or 0101 0101 repeating) during the presence of a maintenance signal. Refer to clause 16.5.

For the case of ODUCn, the content of the PM field, except the STAT subfield, will be undefined (pattern
will be all-1s or 0101 0101 repeating) during the presence of a maintenance signal (e.g., ODUCn-AIS,
ODUCn-LCK). Refer to clause 16.5.

15.8.2.1.1 ODU PM trail trace identifier (TTI)
For path monitoring, a one-byte trail trace identifier (TTI) overhead is defined to transport the 64-byte TTI
signal specified in clause 15.2 or a discovery message as specified in [ITU-T G.7714.1].
The ODUk and ODUCn contain one instance of ODU PM TTI overhead.

The 64-byte TTI signal shall be aligned with the ODU multiframe (see clause 15.6.2.2) and transmitted four
times per multiframe. Byte 0 of the 64-byte TTI signal shall be present at ODU multiframe positions 0000
0000 (0x00), 0100 0000 (0x40), 1000 0000 (0x80) and 1100 0000 (0xC0).

15.8.2.1.2 ODU PM error detection code (BIP-8)
For path monitoring, a one-byte error detection code signal is defined in the ODU PM overhead. This byte
provides a bit interleaved parity-8 (BIP-8) code.
NOTE  The notation BIP-8 refers only to the number of BIP bits and not to the EDC usage (i.e., what quantities are
counted). For definition of BIP-8, refer to the BIP-X definition in [ITU-T G.707].
Each ODU BIP-8 is computed over the bits in the OPU (columns 15 to 3824) area of ODU frame i, and
inserted in the ODU PM BIP-8 overhead location in the ODU frame i+2 (see Figure 15-20).

The ODUk contains one instance of ODU PM BIP-8 overhead. The ODUCn contains n instances of the ODU
PM BIP-8 overhead, numbered 1 to n (BIP-8 #1 to BIP-8 #n).

1139