Does IPv6 define a separate header checksum?

• A. Yes, in the IPv6 header
• B. Yes, there is a 16-bit header checksum
• C. A header checksum exists only in extension headers
• D. No; a header checksum is not defined and checksums are calculated by higher-layer protocols

Answer: (D)

IPv6 removes a separate header checksum to speed up routing and per-hop processing. Instead of protecting the IPv6 header with a checksum, integrity is handled by other layers: the transport protocols (like TCP and UDP) compute their own checksums using a pseudo-header that includes IPv6 addresses and payload length, providing end-to-end integrity. Extension headers do not introduce a header checksum either. ICMPv6 does include its own checksum field, but that belongs to the ICMPv6 header, not the IPv6 header itself. So there is no IPv6 header checksum defined, and checksums are handled by higher-layer (and some control-layer) protocols rather than the IPv6 header.