Traditionally, Ethernet MAC rates were constrained to match the rates of the Ethernet PHY(s). OIF's implementation agreement [OIFMLG3] was the first step in allowing MAC rates to be different than the PHY rates. OIF has recently approved another implementation agreement [OIFFLEXE1] which allows complete decoupling of the MAC data rates and the Ethernet PHY(s) that support them. This includes support for (a) MAC rates which are greater than the rate of a single PHY (satisfied by bonding of multiple PHY(s)), (b) MAC rates which are less than the rate of a PHY (sub-rate), (c) support of multiple FlexE client signals carried over a single PHY, or over a collection of bonded PHY(s). The FlexE SHIM functions which bond multipe Ethernet PHY(s) to form a large "pipe" view the connectivity between two FlexE aware devices as a collection of multiple point-to-point links (one link per Ethernet PHY). These logical point-to-point links can either be direct links (without an intervening transport network), or realized via a Optical transport network. This draft catalogs the usecases that capture the FlexE deployment scenarios -- including the cases that include/exclude OTNs.