IPv6 Packet IPv6

An IPv6 packet — a fixed header plus its payload.

Reading a capture

Thirty-two of the forty octets are addresses. Compare that against IPv4's twenty-octet header carrying eight octets of address: nearly all of the growth is address space, and almost none of it is new machinery.

Subfields

• Version — Always 6 here.
• Traffic Class — Six bits of differentiated services code point and two of explicit congestion notification — the same split as IPv4's DSCP and ECN.
• Flow Label — Labels a sequence of packets the sender wants handled as one flow.
• Payload Length — Octets after this forty-octet header, extension headers included.
• Next Header — What follows this header — a transport protocol, or an extension header.
• Hop Limit — Decremented by each router; the packet dies at zero.
• Source Address — Where the packet came from.
• Destination Address — Where it is going.

Where it sits

IPv6 Packet

• Open in the explorer — UDP over IPv6, in a QoS Data frame

Accuracy

Clause

RFC 8200 §3

Verified

Not verified against the standard. Treat this as a claim, not a fact.