When are IPv4 Options used and how do they affect header length?

• A. Options are optional; if present, they extend the header length beyond 20 bytes.
• B. Options are mandatory in every packet.
• C. Options do not affect header length.
• D. Options set a fixed header length of 40 bytes.

Answer: (A)

IPv4 header length can vary. The base header is 20 bytes, and the length is indicated by the IHL field in 32-bit words. Options are optional data that can be included after the base header; if any options are present, they add to the header size, making it longer than 20 bytes. The header can grow up to 60 bytes (15 words) when options are used. Options provide extra control information (like routing or timestamps), but they aren’t required for every packet, and many networks don’t rely on them. So the correct idea is that options are optional and, when present, extend the header length beyond 20 bytes.