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IPv6 Extension Headers

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IPv6: fixing IPv4's option mess

IPv4's options field was a fixed position in the header that every router had to inspect, slowing forwarding. IPv6 eliminates header options entirely — the base header is always exactly 40 bytes.

Optional information uses extension headers chained via Next Header fields. Routers forward on the Destination Address without inspecting extension headers (except Hop-by-Hop) — enabling fast hardware forwarding.

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