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2 Transport aspects

NOTE – The FlexO frame structure is derived from 100Gbit/s Ethernet clause 91 [IEEE 802.3-2015] FEC alignment and
lane architecture, without any 66b alignment or 256b/257b transcoding functions.

Figure 8-1  FlexO frame structure

8.2 Multi-frame structure
In order to pad the payload area and provide additional OH field locations, an 8-frame multi-frame
structure is defined. The multi-frame structure is shown in Figure 8-2. It uses the three least significant bits
of the multi-frame alignment signal (MFAS) overhead to identify the eight frames within the multi-frame.
The multi-frame contains seven fixed stuff locations, each containing 1,280 bits. These fixed-stuff locations
are distributed in row 65, columns 1 to 1,280 of the first seven frames within the multi-frame. The last
frame within the multi-frame does not contain fixed stuff.
The fixed stuff bits are filled with all-0s and not checked at the receiver sink function.

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