IP options must fall on which boundary?

IP options must fall on which boundary?

• A. 2-byte boundaries
• B. 4-byte boundaries
• C. 8-byte boundaries
• D. 16-byte boundaries

Answer: (B)

IPv4 headers are defined in 32-bit words, and the header length field (IHL) counts how many of those 32-bit words are in the header. Because the total header length must be a multiple of 4 bytes, any options added in the header must start and end on a 4-byte boundary. The base header is 20 bytes (already a multiple of 4), and options extend that length up to a multiple of 4 by padding as needed (often with No-Operation or End-of-Options List markers). This alignment ensures efficient parsing and processing by network devices and software.

IPv4 headers are defined in 32-bit words, and the header length field (IHL) counts how many of those 32-bit words are in the header. Because the total header length must be a multiple of 4 bytes, any options added in the header must start and end on a 4-byte boundary. The base header is 20 bytes (already a multiple of 4), and options extend that length up to a multiple of 4 by padding as needed (often with No-Operation or End-of-Options List markers). This alignment ensures efficient parsing and processing by network devices and software.