Fragment sizes, except possibly the last, are constrained by the MTU.

• A. True
• B. False
• C. Only for UDP
• D. Only when IPv6

Answer: (A)

The main idea here is that the MTU sets the maximum size of any IP fragment on a link. When an IP packet is larger than what a network link can carry, it is broken into smaller pieces so each piece fits within the MTU. Each fragment includes an IP header and a portion of the original payload, and the total length of every fragment cannot exceed the MTU. The last fragment may carry the remaining payload and thus can be smaller than the others, which is why it’s often described as “perhaps the last” being smaller. This constraint applies to all IP traffic, not just UDP, and it’s relevant to both IPv4 and IPv6 fragmentation (though IPv6 handles fragmentation differently at the source and routers, the MTU still governs fragment sizes). If the Don't Fragment flag is set and a packet would require fragmentation, it will be dropped instead of being fragmented.