Patent ID: 7450551

Claim:
A method of processing frame by an optical line termination (OLT) for multicast transmission in a Gigabit-capable passive optical network encapsulation mode (GEM) mode in a Gigabit-capable passive optical network, the method comprising the steps of: a) an OLT receiving a frame from an optical network unit (ONT), which belongs to the OLT, and intercepting an Internet Group Management Protocol (IGMP) frame by means of a media access control (MAC) address of the received frame; b) confirming whether an address of a multicast group, which is included in the IGMP frame, is an address registered to the OLT; c) confirming whether an ONT number coincides with an ONT number registered to the OLT, as a result of the confirmation in step b, when the address of the multicast group is the address registered to the OLT; d) assigning a new multicast port ID to the address of the multicast group, and registering corresponding information to the OLT, as a result of the confirmation in step b, when the address of the multicast group is not the address registered to the OLT; e) assigning a multicast port ID, which has been registered to the address of the multicast group, to the ONT, and registering corresponding information to the OLT, as a result of the confirmation in step c), when the ONT number does not coincide with an ONT number registered to the OLT; and f) transmitting a message to the ONT, the message requiring the multicast port ID having been registered to be assigned to the ONT.