Page 1331 - 5G Basics - Core Network Aspects

Transport aspects 2

Figure 9-5  Multi-frame alignment signal overhead

The MFAS field is located in all frames, in overhead byte 1 immediately following the AM.
9.2.2 Group identification (GID)

A 20-bit (2.5 bytes) FlexO Group Identification field is provided to indicate the FlexO Group instance that
the FlexO interface is a member of. The GID provides the ability to check at the receive side that the FlexO
interface belongs to the intended FlexO group instance.

The GID field is located in frame 1, in overhead bytes 3, 4 and 5.
The same FlexO Group Identification value is used in both directions of transport.

Non-zero values for GID are valid and the value of "0" is reserved for this field.
A FlexO interface that is not part of any group has its GID value set to "0".

9.2.3 PHY identification (PID)
A FlexO group is composed of m FlexO interfaces, also referred to as members or PHYs. An 8-bit (1 byte)
field is provided to uniquely identify each member of a group and the order of each member in the group.
This information is required in the reordering process.

The PID values of the interfaces in a FlexO group are not necessarily arranged consecutively. The PID values
indicate the order of the interfaces within the FlexO group, from low to high. The first FlexO interface in the
group is the one with the lowest PID value.

The PID field is located in frame 1, in overhead byte 6. The values ''0'' and ''255'' are reserved for this field.
The same FlexO PHY Identification value is used in both directions of transport.

A FlexO interface that is not part of any group has its PID value default to "0".
9.2.4 PHY map (MAP)

A 256-bit (8 bytes) field is provided to indicate the members belonging to the group. Each bit in the field, is
set to ''1'' indicating a member/PHY is part of the group. The bit position of the MAP corresponds to the PID
set for the member FlexO interface, with the MSB corresponding to lowest numbered PID. The remaining
unused fields in the MAP are set to ''0''. The full MAP is sent and received on all members of the group.
The MAP field is located in all frames, in overhead bytes 7, 8, 9 and 10. As shown in Figure 9-6, the MSB of
overhead byte 7 in frame 1 is associated with PID #0 and the LSB of overhead byte 10 in frame 8 is
associated with PID #255.

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