Why is there no fragment offset field in an IPv6 packet?

Why is there no fragment offset field in an IPv6 packet?

• A. IPv6 uses a dedicated fragmentation header.
• B. IPv6 relies on routers to fragment packets.
• C. IPv6 hosts adjust their packet sizes to fit network requirements.
• D. IPv6 fragments packets based on DNS information.

Answer: (C)

In IPv6, fragmentation is handled at the endpoints, not by routers along the path. The sending host uses path MTU discovery to figure out the largest packet size that can traverse the whole route, and if a packet is too big for a link it gets dropped and an ICMPv6 “Packet Too Big” message is returned to the source. The source then resends with a smaller size. If fragmentation ever occurs, it’s done by the origin host using a Fragment header, which carries the offset information there, not in the main IPv6 header. This design avoids per-hop fragmentation and keeps the main header compact, so there isn’t a fragment offset field in the IPv6 header itself. The key idea is that hosts adjust packet sizes to fit network requirements rather than relying on routers to fragment.

In IPv6, fragmentation is handled at the endpoints, not by routers along the path. The sending host uses path MTU discovery to figure out the largest packet size that can traverse the whole route, and if a packet is too big for a link it gets dropped and an ICMPv6 “Packet Too Big” message is returned to the source. The source then resends with a smaller size. If fragmentation ever occurs, it’s done by the origin host using a Fragment header, which carries the offset information there, not in the main IPv6 header. This design avoids per-hop fragmentation and keeps the main header compact, so there isn’t a fragment offset field in the IPv6 header itself. The key idea is that hosts adjust packet sizes to fit network requirements rather than relying on routers to fragment.