An entry that contains objects used to manage a logical or
physical interface representing a single elementary packet
stream at the point where the CDL path defect indications are
terminated. Typically, this is a point where the CDL Ethernet
encapsulation is applied and removed. This can also be a point
between a part of the CDL network that supports
packet-by-packet multiplexing, and a part of the CDL network
that does not support packet-by-packet multiplexing.
This interface may have ifType value other than
'ethernetCsmacd', if traffic from a non-Ethernet protocol is
received on this interface and then encapsulated (or otherwise
interworked) in Ethernet and then CDL, before being progressed
into the CDL network.