Values used by the PPPoE header's code field, distinguishing Session
data from the five Discovery stage packet types.
SESSION_DATA: number
Session stage data — the payload carries a PPP frame.
PADO: number
PPPoE Active Discovery Offer, sent by an Access Concentrator in reply to a PADI.
PADI: number
PPPoE Active Discovery Initiation, broadcast by a Host to begin Discovery.
PADR: number
PPPoE Active Discovery Request, sent by a Host to the chosen Access Concentrator.
PADS: number
PPPoE Active Discovery Session-confirmation, sent by an Access Concentrator in reply to a PADR.
PADT: number
PPPoE Active Discovery Terminate, sent by either peer to end a session.