Final answer:
A receiving node identifies the beginning and end of a frame through the header and trailer in the frame.
Step-by-step explanation:
When data travels on a network, it is encapsulated in frames. These frames contain a header and a trailer that help the receiving node identify the beginning and end of the frame.
The header typically contains information such as the source and destination addresses, sequence numbers, and control bits. The receiving node uses this header information to identify the start of the frame.
The trailer often includes a checksum or a cyclic redundancy check (CRC) value. The receiving node can compare this value to the data in the frame to ensure that it hasn't been corrupted during transmission. When the receiving node verifies the checksum or CRC value, it knows that it has reached the end of the frame.