Which statement describes a characteristic of the frame header fields of the data link layer?
- They all include the flow control and logical connection fields.
- Ethernet frame header fields contain Layer 3 source and destination addresses.
- They vary depending on protocols.
- They include information on user applications.
Explanation: All data link layer protocols encapsulate the Layer 3 PDU within the data field of the frame. However, the structure of the frame and the fields that are contained in the header vary according to the protocol. Different data link layer protocols may use different fields, like priority/quality of service, logical connection control, physical link control, flow control, and congestion control.