During fragmentation, which fields are essential to reassemble the original packet on the receiving end?

• A. Version, IHL, and Total Length
• B. Identification, Flags, and Fragment Offset
• C. Type of Service and Protocol
• D. Source Address and Destination Address

Answer: (B)

The thing being tested is how reassembly of fragmented IPv4 packets is done. To put the pieces back together, the receiver relies on three fields: Identification, Flags (specifically the More Fragments bit), and Fragment Offset. The Identification value ties all fragments that belong to the same original datagram, so fragments from different packets aren’t mixed up. The Fragment Offset tells where each fragment’s payload fits in the original data, and it’s expressed in 8-byte units, which lets the receiver place each piece in the correct order. The More Fragments flag indicates whether more fragments follow this one; when it’s not set, that fragment is the last piece. Together, these fields let the receiver collect all relevant fragments and reconstruct the complete payload accurately. Other fields, such as Version/IHL, Type of Service, Protocol, or the Source and Destination addresses, are important for routing and processing, but they aren’t used to reassemble the payload.