#Ethernet
---
protocol: &ethframe
  name: eth-frame
  osilayer: 2
  fields:
    - field: dstmac
      desc: destination MAC
      length: 6
    - field: srcmac 
      desc: source MAC
      length: 6
    - field: vlantag
      desc: VLAN tag
      length: 4
      subfields: 
        - field: tpid
          desc: tag protocol identifier (0x8100)
          length: 2
        - field: tci
          desc: tag control information
          length: 2
          subfields:
            - field: pcp
              desc: priority code point (PCP)
              bitfield: yes
              length: 3
            - field: dei
              desc: drop eligible indicator (DEI)
              bitfield: yes
              length: 1
            - field: vid
              desc: VLAN identifier (VID)
              bitfield: yes
              length: 12
    - field: protocolid
      desc: Ethertype (Eth II) or length (IEEE 802.3)
      length: 2
      nextlayer: yes
    - field: data
      data: true
    - field: CRC
      desc: FCS (32-bit CRC)
      length: 4
      optional: yes #most network stacks compute that automatically