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Transport aspects 2

15.8.2.2.2 ODU TCM error detection code (BIP-8)

For each tandem connection monitoring field, a one-byte error detection code signal is defined in the ODU
TCMi 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 TCM BIP-8 is computed over the bits in the OPU (columns 15 to 3824) area of ODU frame i, and
inserted in the ODU TCM BIP-8 overhead location (associated with the tandem connection monitoring
level) in ODU frame i+2 (see Figure 15-23).
The ODUk contains one instance of ODU TCMi BIP-8 overhead. The ODUCn contains n instances of the ODU
TCMi BIP-8 overhead, numbered 1 to n (BIP-8 #1 to BIP-8 #n).

Figure 15-23  ODU TCM BIP-8 computation

15.8.2.2.3 ODU TCM backward defect indication (BDI)
For each tandem connection monitoring field, a single-bit backward defect indication (BDI) signal is defined
to convey the signal fail status detected in a tandem connection termination sink function in the upstream
direction.

BDI is set to "1" to indicate an ODUk backward defect indication; otherwise, it is set to "0".
The ODUk and ODUCn contain one instance of ODU TCMi BDI overhead.

15.8.2.2.4 ODU TCM backward error indication (BEI) and backward incoming alignment error
(BIAE)

For each tandem connection monitoring field, a 4-bit backward error indication (BEI) and backward
incoming alignment error (BIAE) signal is defined. This signal is used to convey in the upstream direction the
count of interleaved-bit blocks that have been detected as being in error by the corresponding ODU
tandem connection monitoring sink using the BIP-8 code. It is also used to convey in the upstream direction
an incoming alignment error (IAE) condition that is detected in the corresponding ODU tandem connection
monitoring sink in the IAE overhead.

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