What is the 2-byte type field used for in an Ethernet frame?

A. It defines the data type contained within the frame.
B. It identifies the upper-layer protocol for the data contained within the frame.
C. It is a calculation with the FCS to provide error detection.
D. It describes the length of data contained within the frame.

B. The Ethernet type field is 2 bytes and it identifies at layer 2 which upper-layer protocol to send the data to. When IPv4 is used, the type field is 08-00. When IPv6 is used, the type field is 86-dd.