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Transport aspects 2

Figure 7-1  FlexO group principal information containment relationship

7.2 Process flow

Functions and process flows are specified in [ITU-T G.798].

8 FlexO frame
A FlexO frame is associated with a FlexO interface and is independent of an OTUCn frame and transport
unit, the latter being specified in [ITU-T G.709]. The OTUCn is the transport unit over OTN interfaces.
A FlexO frame consists of frame alignment (markers), OH, FEC and payload area.

The FlexO frames in the different interfaces of a FlexO group are frame/multi-frame aligned at the source.

8.1 Frame structure
The frame structure is shown in Figure 8-1 and consists of 128 rows by 5,440 1-bit columns. It contains a
frame alignment marker area in row 1, columns 1 to 960, an overhead area in row 1 columns 961 to 1280, a
FEC area in columns 5,141 to 5,440 in every row and a (128 × 5140 – 1280 = 656640 bit) payload area in the
remainder of the frame. The FlexO frame period results is ~6.2us.

Each row constitutes a 5,440-bit FEC codeword, with the last 300 bits used for the FEC parity bits. This
results in a bit-oriented structure. The MSB in each FEC codeword is bit 1, the LSB is bit 5,440.

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