---
protocol:
  name: ipv4
  longname: internet protocol version 4
  osilayer: 3
  fields:
    - field: version
      desc: Version
      bitfield: yes
      length: 4
    - field: IHL
      desc: internet header length (IHL)
      bitfield: yes
      length: 4
    - field: DSCP
      desc: differential services code point (DSCP)
      bitfield: yes
      length: 6
    - field: ECN
      desc: explicit congestion notification (ECN)
      bitfield: yes
      length: 2
    - field: packetlength
      desc: total length (incl. header)
      length: 2
    - field: id
      desc: identification
      length: 2
    - field: flags
      desc: fragment flags
      bitfield: yes
      length: 3
      subfields:
        - field: reserved
          bitfield: yes
          length: 1
        - field: df
          desc: don't fragment (DF)
          bitfield: yes
          length: 1
        - field: mf
          desc: more fragments (MF)
          bitfield: yes
          length: 1
    - field: fragmentoffset
      desc: fragment offset
      bitfield: yes
      length: 13
    - field: TTL
      desc: time to live (TTL)
      length: 1
    - field: protocol
      desc: protocol id
      length: 1
    - field: headerchecksum
      desc: header checksum
      length: 2
    - field: source
      desc: source ip address
      length: 4
    - field: destination
      desc: destination ip address
      length: 4
    - field: options
      desc: options (if IHL > 5)
      length: 4
      optional: yes
    - field: data
      data: true