VeEX UX400, User Manual

Page: 159 / 209

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
Z5 Byte (Path TCM)
V5 byte (VT path overhead)
The first byte of a VT SPE provides the functions of error checking, signal label and path status.
Continuous monitoring of anomalies or defects and payload composition at the path end or along the path
Bits 1-2 provides error checking (BIP-2)
Bit 3 is the REI-V (0 = no error, 1 = errors), that is sent back towards an originating VT PTE if errors were detected by the BIP-2.
Bit 4 is reserved for mapping-specific functions.
UX400 10G e-Manual D07-00-058P RevA00 Page 159 of 209