The Fragment Offset field is how many bits wide?

• A. 12 bits
• B. 13 bits
• C. 14 bits
• D. 16 bits

Answer: (B)

In IPv4, the Fragment Offset field tells you where a fragment’s payload fits within the original datagram. It’s expressed in units of eight bytes, which means each value references eight-byte blocks rather than individual bytes. The field is 13 bits wide because the 16-bit combined field that carries both this offset and the Flags uses 3 bits for Flags and the remaining 13 bits for the offset. That gives offsets from 0 up to 8191 (0 to 8191 × 8 bytes), which allows describing the position of fragments while staying within the overall 65,535-byte limit of an IP datagram (including the header). This structure enables proper reassembly at the destination, with the MF (More Fragments) flag indicating whether more pieces follow.