VeEX RXT-6000e, User Manual

Page: 158 / 387

H4 Byte (VT Indicator)
Z3/Z4 byte (STS Path)
Allocated for future use. Have no defined value. The receiver is required to ignore their content.
Z5 byte (STS Path TCM)
Allocated to provide a STS Path Tandem Connection monitoring function for contiguously concatenated
STS-3 levels.
Bits 1-4: Used as an Incoming Error Count (IEC)
Bit 5: Operates as the TC-REI to indicate errored blocks occurring within the tandem connection
Bit 6: Operates as the OEI to indicate errored blocks egressing the STS-n
Bits 7-8: Operate in 76 multi-frame structure:
Frames 1-8 > Frame Alignment Signal (FAS)
Frames 9-72 > The Access Point Identifier of the Tandem Connection (TC-API)
Frames 73-76 > TC-RDI indicating defects that have occurred in the tandem connection to the far-
end
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
Frames 73-76 > Reserved capacity
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