Page 107 - ITU-T Focus Group IMT-2020 Deliverables

ITU-T Focus Group IMT-2020 Deliverables 3

6.1.7.4.2 FlexE Client

A FlexE client is an Ethernet data flow, encoded as a 64B/66B according to Figure 82-5 of IEEE 802.3
[Ref.6.1.7-2]. The implementation agreement at OIF [Ref.6.1.7-1] requires that Ethernet MAC operating at a
rate of 10, 40, or m × 25 Gb/s (m >= 1).

6.1.7.4.3 FlexE Shim
FlexE shim is a layer on the FlexE interface, and it performs functions including the following:
1) On transmission, the FlexE shim maps FlexE clients (Ethernet packets) over the FlexE group in the
form of 64B/66B. This function is also called FlexE mux.
2) On reception, the FlexE shim demaps FlexE clients from the FlexE group in the form of 64B/66B to
Ethernet packets. This function is also called FlexE demux.

6.1.7.4.4 FlexE Calendar
Per [Ref.6.1.7-1], the FlexE mechanism operates using a calendar which assigns 66B block positions on sub-
calendars on each PHY of the FlexE group to each of the FlexE clients. The calendar has a granularity of 5G,
and has a length of 20 slots per 100G of FlexE group capacity. Two calendar configurations are supported: an
“A” and a “B” calendar configuration. At any given time, one of the calendar configurations is used for
mapping the FlexE clients into the FlexE group and demapping the FlexE clients from the FlexE group. Refer
to the illustration of Figure 6.1.7-2 (source is from OIF [Ref.6.1.7-1]).

Figure 6.1.7-2 – Illustration of FlexE Calendar and Overhead on each Ethernet PHY

6.1.7.4.5 FlexE Overhead

The alignment of the data from the PHYs of the FlexE group is accomplished by the insertion of FlexE
overhead into the stream of 66B blocks carried over the group. The FlexE overhead is delineated by a 66B
block which can be recognized independently of the FlexE client data.

6.1.7.4.6 Capabilities of FlexE
FlexE has three general capabilities [Ref.6.1.7-1] as follows:
1) Bonding Ethernet PHYs
FlexE allows bonding multiple Ethernet PHYs as a larger pipe to carry a FlexE data flow. E.g., a data
flow of MAC rate 200G can be carried over on two bonded Ethernet 100G PHYs.
2) Sub-rating of Ethernet PHYs
FlexE allows a data flow with MAC rate less than that of an Ethernet PHY be carried over. E.g., a data
flow of MAC rate 50G can be carried over on a single Ethernet 100G PHY.

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