EXFO FTB-8510B Guia Del Usuario página 1317

Glossary
Next-Gen - Virtual Concatenation (VCAT)
High-Order Path Sequence Indicator
In addition to the MFI, the H4 byte also carries the sequence indicator
information. The sequence indicators are assigned by the source node
(PTE) and interpreted by destination node (PTE). The sequence
indicator (SQ) identifies the order in which the STS-1/STS-3c of a
SONET STS-1/STS-3c-Xv is assembled to create the contiguous
container (STS-1/STS-3c-Xc), as demonstrated in figure below.
Similarly, SQs are used to identify the order of VC-3/VC-4s used to
create the VC-3/4-Xc in SDH.
Sequence Indicator in High-Order Path VCAT Multiframe
The eight-bit SQ, supporting a range from 0 to 255, is formed by using
the H4 bytes (bits 1 to 4 of frame 14 and 15) in the first multiframe stage
(MFI1), as shown in figure H4 High-Order Path Multiframe Structure on
page 666. Each VCG member is assigned an SQ. Normally, the first
timeslot associated to a VCG, composed of STS-1/3c-Xv or VC-3/4-Xv, is
667
SONET/SDH Application