IHL

Header length in 32-bit words. Five means a twenty-octet header with no options.

Reading a capture

Must be read before anything after the header can be located. A decoder that assumes twenty octets breaks on any packet carrying options.

Where it sits

IPv4 Datagram > IHL

• Open in the explorer — TCP over IPv4, in a protected QoS Data frame, aggregated
• Open in the explorer — ICMP echo over IPv4, in a QoS Data frame
• Open in the explorer — TCP over IPv4, in a protected QoS Data frame
• Open in the explorer — TCP over IPv4, in an open QoS Data frame
• Open in the explorer — UDP over IPv4, in a QoS Data frame

Accuracy

Clause

RFC 791 §3.1

Verified

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