Method for transmitting oam message and processing error in pon system

PURPOSE: An OAM(Operation, Administration, and Maintenance) message transmission method in a PON(Passive Optical Network) system and error processing method are provided to simplify an OAM message transmission and reception procedure by using an OAM packet type including a variable length. CONSTITUTION: An OLT(Optical Line Terminal) transmits created OAM messages to an ONU(Optical Network Unit). The OLT receives a response OAM message from the ONU(S502). The created OAM message includes a message identifier for one or more ethernet switching control creation messages, message content lengths, and a message content field. The created OAM message includes the message identifier, the message content lengths, and the message content field for one or more ethernet switching control response messages.