Z5 byte (STS Path TCM)
- Allocated to provide a STS Path Tandem Connection monitoring function for contiguously concatenated STS-3 levels.
o Bits 1-4: Used as an Incoming Error Count (IEC)
o Bit 5: Operates as the TC-REI to indicate errored blocks occurring within the tandem connection
o Bit 6: Operates as the OEI to indicate errored blocks egressing the STS-n
o Bits 7-8: Operate in 76 multi-frame structure;
- Frames 1-8 >Frame Alignment Signal (FAS)
o Frames 9-72 > The Access Point Identifier of the tandem connection (TC-API)
o Frames 73-76 > TC-RDI indicating defects that have occurred in the tandem connection to the far end
o Frame 74 > ODI indicating to the far end that AU/TU-AIS has been inserted into egressing STS-n / VTG-n due to
defects before or within the tandem connection
o Frames 73-76 > Reserved capacity
TX150 e-Manual D07-00-023 Rev A02
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