# PBB

class `ryu.lib.packet.pbb.``itag`(pcp=0, dei=0, uca=0, sid=0)

  I-TAG (IEEE 802.1ah-2008) header encoder/decoder class.

  An instance has the following attributes at least. Most of them are same to the on-wire counterparts but in host byte order. __init__ takes the corresponding args in this order.

  Attribute | Description
  --- | ---
  pcp | Priority Code Point
  dei | Drop Eligible Indication
  uca | Use Customer Address
  sid | Service Instance ID

  classmethod `parser`(buf)

    Decode a protocol header.

    This method is used only when decoding a packet.

    Decode a protocol header at offset 0 in bytearray buf. Returns the following three objects.

    - An object to describe the decoded header.
    - A packet_base.PacketBase subclass appropriate for the rest of the packet. None when the rest of the packet should be considered as raw payload.
    - The rest of packet.
  `serialize`(payload, prev)

    Encode a protocol header.

    This method is used only when encoding a packet.

    Encode a protocol header. Returns a bytearray which contains the header.

    payload is the rest of the packet which will immediately follow this header.

    prev is a packet_base.PacketBase subclass for the outer protocol header. prev is None if the current header is the outer-most. For example, prev is ipv4 or ipv6 for tcp.serialize.