Answer:
Data offset field
Step-by-step explanation:
The data offset field is used to store the size of the Transmission Control Protocol (TCP) header. The size of the Transmission Control Protocol (TCP) header is stored using a four bit number so that the receiving network device understands where the actual data payload begins. The minimum size of the header has 5 data offset words (representing 20 bytes) while the maximum size of the header has 15 data offset words (representing 60 bytes).
