KR20100061263A - Olt and method for transmitting broadcast frame in gpon - Google Patents

Abstract

PURPOSE: An OLT(Optical Line Terminal) in a GPON(Gigabit Passive Optical Network) and a method for transmitting a broadcast frame using the same are provided to retransmit a broadcast frame downstream without having to manage an Ethernet address and an IP address. CONSTITUTION: A PON(Passive Optical Network) connects an OLT(Optical Line Terminal)(10) installed in a telephone office to ONUs(Optical Network Units)(20), also called ONTs(Optical Network Terminals), installed in a home through a passive optical splitter in a point to multi-point scheme. A downstream transmission from the OLT to the optical network unit is performed through a broadcast transmission scheme allowing all packets to be transmitted to the optical network unit. However, an upstream transmission from the optical network units to the optical line terminal is performed by sharing a single optical link with a plurality of optical network units based on various medium access control schemes. A broadcast frame, such as an ARB packet, needs to be output through ports except for a port of an Ethernet switch which has transmitted the broadcast frame. When transmitting a broadcast frame in the GPON(Gigabit Passive Optical Network), two transmission paths are considered based on the direction of a transmission.

Description

Broadcasting frame transmission method of optical line terminal and optical line terminal in Gigabit passive optical communication network {OLT and method for transmitting broadcast frame in GPON}

One aspect of the present invention relates to a gigabit passive optical communication network technology, and more particularly, to an optical line terminal and a broadcast frame transmission method of an optical line terminal in a gigabit passive optical communication network.

This study was derived from the research conducted as part of the experimental project for the development of optical subscriber network (FTTH) services by the Ministry of Knowledge Economy and the Ministry of Information and Communication Research.

Gigabit-capable Passive Optical Networks (GPONs) provide broadband to subscribers and accommodate a variety of multi-protocols. GPON is one of the standardized FTTH (Fiber To The Home) services through ITU-T, and many optical subscriber units (Optical Network Terminal, ONT or Optical Network Unit, ONU) are connected to a single optical line terminal through passive devices. Optical Line Terminal (OLT) has a structure that is connected in a point-to-multipoint method.

An optical line terminal is a multiservice device that connects an optical subscriber network with other systems, and is composed of a SIPP (Service Interface and Protocol Processing) device, a comprehensive cable broadcasting (CATV) device, a transmission device, and a network management device. An optical subscriber device is a network termination device for accessing an optical subscriber system system constituting a next generation communication network. Optical subscriber equipment converts communication interface or video signal interface such as N-ISDN user-network interface and B-ISDN user-network interface to connect to optical fiber network. do.

According to an aspect, a gigabit passive optical communication network provides an optical line terminal and a broadcast frame transmission method capable of retransmitting a broadcast frame downward without managing an Ethernet address and an IP address.

According to an aspect, an optical line terminal in a gigabit passive optical communication network may include a port identifier assigned for each optical subscriber device and an antiport identifier assigned for each optical subscriber device so that broadcast frames are not retransmitted to the optical subscriber device that has transmitted the broadcast frame. Receiving a broadcast frame from the identifier table and the optical subscriber device, respectively, to store the information, the controller to configure and provide a broadcast frame by changing the port identifier of the broadcast frame to an anti-port identifier matching the port identifier with reference to the identifier table It includes.

Meanwhile, a method of transmitting a broadcast frame of an optical line terminal in a gigabit passive optical communication network according to another aspect includes receiving an uplink broadcast frame from an optical subscriber device, storing a port identifier and an antiport identifier assigned to each optical subscriber device. Referencing the identifier table, changing the port identifier of the broadcast frame to an anti-port identifier that matches the port identifier to construct a broadcast frame and transmitting the configured broadcast frame downward.

On the other hand, an information storage medium recording the data structure of an optical line terminal in a gigabit passive optical communication network according to another aspect is allocated to each optical subscriber unit so that the broadcast frame is transmitted to the optical subscriber unit that has transmitted the broadcast frame to the optical line terminal. The port subscriber information and the optical subscriber device which has transmitted the broadcast frame to the optical line terminal include anti-port identifier information allocated for each optical subscriber device so that the broadcast frame is not retransmitted.

According to one embodiment, an optical port terminal in a gigabit passive optical network assigns and manages an anti-port identifier to the optical subscriber device that transmits the broadcast frame to the optical terminal so that the broadcast frame is not retransmitted. Even if the IP address is not managed, the broadcast frame can be retransmitted downward.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention; In the following description of the present invention, if it is determined that detailed descriptions of related well-known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to intention or custom of a user or an operator. Therefore, the definition should be made based on the contents throughout the specification.

1 is an exemplary diagram illustrating a gigabit passive optical communication network to which the present invention is applied.

Referring to FIG. 1, a Passive Optical Network (PON) includes an optical line terminal (OLT) 10 installed at a telephone station and an optical subscriber unit (ONU or ONT) 20 located at each subscriber's premises or in an incoming facility. ), Unlike the existing communication concept, connects in a point-to-multipoint manner through the passive optical splitter 30. In the downstream direction from the optical line terminal 10 to the optical subscriber unit 20, a broadcast scheme in which all packets are transmitted to all optical subscriber units 20 is used.

However, the upstream direction from each optical subscriber device 20 to the optical line terminal 10 is used by a method in which one optical link is shared by several optical subscriber devices 20 using various media approaches. do. One of the media access methods, Time Division Multiple Access (TDMA) PON, uses a time division multiple access scheme that is accessible only at a time when transmission is allowed from the optical line terminal 10, and in particular, a gigabit passive optical communication network (Gigabit) to which the present invention belongs. Capable Passive Optical Network (GPON) corresponds to TDMA PON.

2 is an exemplary diagram for explaining uplink frame transmission of an optical line terminal according to an embodiment of the present invention.

Referring to FIG. 2, broadcast frames such as ARP packets should be output to all ports except ports input from an Ethernet switch. In GPON, a broadcast frame may consider two paths depending on the delivery direction.

The first is a path through which frames are input from the downlink external network. At this time, the frame input from the downlink external network should be delivered to all optical subscriber devices.Because of the structure of the PON system, all frames are broadcasted, so that all optical subscriber devices receive frames when using the broadcast port ID. No problem.

The second is a path through which the frame is input from the optical subscriber device. Assuming that the n-th optical subscriber device 20n transmits the broadcast frame upward 200, as shown in FIG. 2, the optical line ending 10 transmits the received broadcast frame to the optical line terminal 10. FIG. The transmission 210 is also transmitted to the external network, and is also transmitted 220 to the other first optical subscriber device 20a and the second optical subscriber device 20b connected to the optical line terminal 10 at the same time. However, if the above-mentioned frame is broadcasted downward, the n-th optical subscriber device 20n also receives the broadcast frame transmitted by itself, which is received by the Ethernet switch in the n-th optical subscriber device 20n. In this case, the same frame as the transmitted frame may be received again by the output port.

In general GPON, all the Ethernet frame addresses and IP addresses connected to the optical subscriber device are managed by the optical line terminal or the upper router, and the corresponding optical subscriber device is found so that only the optical subscriber device can receive the destination optical subscriber device of the upstream broadcast frame. Send with a Port ID of. Therefore, in order for the optical line terminal to operate normally, frame processing functions of the network layer 2 and layer 3 for determining the port identifier are required. Managing the addresses and IP addresses of the aforementioned Ethernet frames is a very complex and difficult task.

However, according to an embodiment of the present invention, the optical line terminal 10 may satisfy the GPON standard specification and may be broadcast frame to an optical subscriber device that transmits the broadcast frame to the optical line terminal regardless of the Ethernet frame address and IP address. Assign an Anti-Port ID (APID) to prevent this retransmission. The antiport identifier is an identifier assigned to each optical subscriber device so that the broadcast frame is not retransmitted to the optical subscriber device that has transmitted the broadcast frame to the optical line terminal. Accordingly, when the uplink broadcast frame is received from the specific optical subscriber device by the optical line terminal, the broadcast frame can be retransmitted to all other optical subscriber devices except for the specific optical subscriber device.

3 is a block diagram of an optical line terminal according to an embodiment of the present invention. Referring to FIG. 3, the optical line terminal 10 includes an identifier table 110, a controller 100, a downlink receiver 130, a downlink transmitter 140, an uplink transmitter 150, and an uplink receiver 160. The port identifier allocator 120 may be further included.

The identifier table 110 stores a port identifier (Port ID, PID) and an anti-port identifier (Anti-Port ID, APID) allocated to each optical subscriber device. At this time, the port identifier is a port identifier registered in the optical subscriber device so that one optical subscriber device to which the port identifier is assigned can receive the downlink frame transmitted by the optical line terminal.

The antiport identifier is an identifier assigned to each optical subscriber device so that the broadcast frame is not retransmitted to the optical subscriber device that has transmitted the broadcast frame to the optical line terminal.

When the controller 100 receives the broadcast frame from the optical subscriber device, the controller 100 changes the port identifier of the broadcast frame to an anti-port identifier matched with the port identifier by referring to the identifier table 110 to configure the broadcast frame. The broadcast frame is provided to the optical subscriber device. In this case, the controller 100 may retransmit the broadcast frame to another optical subscriber device except for the optical subscriber device that has transmitted the broadcast frame using the anti-port identifier.

Meanwhile, the downlink receiver 130 receives an Ethernet frame from the system external network. In this case, a port ID assigned through the port identifier allocator 120 to be described later is added to the received Ethernet frame, thereby converting the Ethernet frame into a GEM frame (GPON Encapsulation Method frame).

The downlink transmitter 140 performs various GPON related Media Access Control (MAC) functions necessary for transmitting broadcast frames to the optical subscriber device, and generates and manages a GTC frame (GPON Transmission Convergence layer).

The uplink transmitter 150 converts the GEM frame received from the optical subscriber device into an Ethernet frame and transmits it to the system external network.

The uplink receiver 160 performs a GPON MAC function for extracting a GTC frame and a GEM frame received from the optical subscriber device from the optical subscriber device.

Meanwhile, the port identifier allocator 120 allocates and manages a port identifier used in the GPON system. In GPON, up to 4,096 (2 ¹² ) port identifiers can be used, and depending on the purpose, they can be used for multicast frames, broadcast frames, OMCI GEM frames, or general bidirectional data frames.

The optical line terminal assigns a port identifier to the optical subscriber device every time the system is started or the optical subscriber device is added. Then, the optical subscriber apparatus divides the port identifier assigned from the optical line terminal into each frame group, adds it to the port identifier region in the GEM frame header, and transmits the same to the optical line terminal. As described above, since the optical subscriber apparatus inserts and transmits an appropriate port identifier in the frame header among the port identifiers allocated from the optical circuit terminal, the optical subscriber station can easily identify the optical subscriber apparatus identifier to which the received frame belongs.

Here, the port identifier includes a port identifier for an anti-port identifier (APID) frame, and APID is an identifier registered to the optical subscriber device so that all optical subscriber devices except one optical subscriber device can receive. The APID region may be assigned a port identifier whose region does not overlap with other port identifiers within the 4K port identifier determined by the GPON, and as many as the number of optical subscriber devices operated. Therefore, the APID is not a port identifier randomly generated by the port identifier allocator 120, but is a port identifier used for APID use among existing port identifiers, and thus satisfies the GPON standard.

The optical line terminal allocates as many APIDs as the number of optical subscriber devices connected to the network, and registers the number of APIDs corresponding to a specific optical subscriber device to each optical subscriber device among the allocated APIDs.

In the example of an optical line terminal having eight optical subscriber devices connected thereto, it is assumed that eight necessary port identifiers for APID are assigned, and the assigned port identifiers are APID0 to APID7. When eight optical subscriber devices are designated as optical subscriber devices 0 to optical subscriber device 7, a port identifier having APID1 to APID7 except APID0 is registered in optical subscriber device 0, and APID0 and APID2 except APID1 to optical subscriber device 1 Register a port identifier with APID7. The remaining optical subscriber devices can also register seven port identifiers not received only by the above-described method.

The optical subscriber device according to one embodiment receives or discards the downlink frame according to whether the downlink frame received from the optical line terminal is registered in the port identifier registration table. Therefore, when the optical line terminal transmits the frame having the APID3 port identifier, since the APID3 is not registered only in the optical subscriber device 3, all the optical subscriber devices except the optical subscriber device 3 can receive the frame.

4 is a detailed configuration diagram of the control unit 100 of FIG. 3 according to an embodiment of the present invention. Referring to FIG. 4, the controller 100 of FIG. 3 includes a bridge 1010, an identifier change unit 1020, and a multiplexer 1030.

The bridge 1010 determines whether an uplink frame received from the optical subscriber device is a broadcast frame. Here, the bridge 1010 transmits the received uplink frame to the uplink transmitter (150 in FIG. 3) if the received uplink frame is not a broadcast frame, and uplink transmitter (150 in FIG. 3) and the identifier change unit 1020 to be described later if the broadcast frame is a broadcast frame. Simultaneously transmit a frame to control the frame to be retransmitted downward.

Meanwhile, the identifier change unit 1020 registers and retrieves an antiport identifier (APID) used when retransmitting a broadcast frame received upward from the optical subscriber device to the optical subscriber device. Since the optical line terminal allocates a port identifier (PID) to the optical subscriber unit, the optical line terminal can know which optical subscriber unit has transmitted the broadcast frame by looking at the port identifier of the frame received at the optical line terminal. In addition, it is possible to identify the port identifier for the APID corresponding to the optical subscriber device that has transmitted the above-described broadcast frame through the port identifier for each optical subscriber device inputted from the port identifier allocator 120 (FIG. 2) and the APID relationship. Can be.

According to one embodiment, the optical line terminal records APID data in an identifier table (PID-APID table) (110 in FIG. 2) having a port identifier as an address. For example, if the number of optical subscriber devices to be operated is four, each of the optical subscriber devices 0 (ONU0), optical subscriber device 1 (ONU1), optical subscriber device 2 ( ONU2) and optical subscriber unit 3 (ONU3), and a port identifier can be assigned to each optical subscriber unit ONU0, ONU1, ONU2, and ONU3.

As shown in Table 1, when an identifier table (PID-APID table) is recorded, an address becomes a data PID and the table data becomes an APID. If the port identifier of the broadcast frame received from the optical subscriber station by the optical line terminal is 405, 405 is a port identifier of the optical subscriber unit 2 (ONU2). Here, the optical line terminal changes the port identifier of the corresponding frame from 405 to 102 and retransmits it to each optical subscriber device. Then, all of the optical subscriber devices ONU0, ONU1, and ONU3 except for the optical subscriber device 2 (ONU2) having APID 102 of the optical subscriber devices can receive the broadcast frame transmitted by the optical line terminal.

On the other hand, the multiplexer 1030 performs a multiplexing function for the broadcast frame that needs to be retransmitted to the optical subscriber device in the down frame and the up frame. In this case, since the broadcast frame received from the uplink does not have a high frequency, it does not affect the overall downlink performance and may be preferentially output than the received downlink frame.

5 is a flowchart illustrating a method of transmitting an uplink frame of an optical line terminal according to an embodiment of the present invention.

Referring to FIG. 5, the optical line terminal receives an uplink broadcast frame from the optical subscriber device (S500). Subsequently, the port identifier and the antiport identifier are referred to the stored identifier table (S510).

The optical line terminal configures the broadcast frame by changing the port identifier of the broadcast frame to an anti-port identifier matching the port identifier (S520). In this case, the method may further include multiplexing the broadcast frame.

Subsequently, the optical line terminal transmits the broadcast frame downward to the optical subscriber device based on the changed anti-port identifier (S530).

In summary, an optical fiber terminal assigns and manages anti-port identifiers that can be received by all optical subscribers except specific optical subscribers, so that the broadcast frame is downstream from the GPON MAC chip without managing Ethernet and IP addresses. Can be resent.

The embodiments of the present invention have been described above. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1 is a diagram illustrating a gigabit passive optical communication network to which the present invention is applied;

2 is an exemplary diagram for explaining uplink frame transmission of an optical line terminal according to an embodiment of the present invention;

3 is a configuration diagram of an optical line terminal according to an embodiment of the present invention;

4 is a detailed block diagram of the control unit of FIG. 3 according to an embodiment of the present invention;

5 is a flowchart illustrating a method of transmitting an uplink frame of an optical line terminal according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

1: Gigabit Passive Optical Network 10: Optical Line Terminal

20: optical subscriber device 30: passive optical splitter

100 control unit 110 identifier table

120: port identifier allocator 130: downlink receiver

140: downlink transmitter 150: uplink transmitter

160: uplink receiver 1010: bridge

1020: identifier change unit 1030: multiplexer

Claims (11)

In the optical line terminal for a gigabit passive optical network, An identifier table for storing an assigned port identifier for each optical subscriber device and an antiport identifier assigned for each optical subscriber device so that the broadcast frame is not retransmitted; And Receiving a broadcast frame from the optical subscriber device, by referring to the identifier table to change the port identifier of the broadcast frame to an anti-port identifier matching the port identifier comprises a control unit for configuring and providing the broadcast frame; Optical line terminal, characterized in that. The method of claim 1, wherein the control unit, A bridge unit for determining and switching whether an uplink frame received from the optical subscriber device is a broadcast frame; An identifier change unit configured to change the port identifier of the broadcast frame to an anti-port identifier matching the port identifier to form a broadcast frame; And And a multiplexer which controls downlink transmission by multiplexing the configured broadcast frame. The method of claim 1, And a port identifier allocator for allocating the port identifier and the antiport identifier to the optical subscriber device. The method of claim 3, wherein the port identifier assigning unit, Assign the antiport identifier to the optical subscriber device according to the number of the optical subscriber devices; And registering an antiport identifier other than the antiport identifier assigned to a specific optical subscriber device among the assigned antiport identifiers in the specific optical subscriber device. The method of claim 3, wherein the port identifier assigning unit, And assigning the port identifier and the antiport identifier to an area not overlapping with each other. The method of claim 1, wherein the control unit, And providing the broadcast frame to another optical subscriber device except for the optical subscriber device which has transmitted the broadcast frame using the anti-port identifier. A broadcast frame transmission method of an optical line terminal for a gigabit passive optical communication network, Receiving an uplink broadcast frame from an optical subscriber device; Configuring a broadcast frame by changing a port identifier of the broadcast frame to an antiport identifier matching the port identifier with reference to an identifier table storing an assigned port identifier and an antiport identifier for each optical subscriber device; And Transmitting the configured broadcast frame downward; And the anti-port identifier is an identifier registered in the optical subscriber device such that the broadcast frame is not retransmitted to the optical subscriber device that has transmitted the broadcast frame to the optical wire terminal. The method of claim 7, wherein the step of configuring the broadcast frame by changing the port identifier to the anti-port identifier, Determining whether the uplink frame received from the optical subscriber device is a broadcast frame and switching; Configuring a broadcast frame by changing a port identifier of the broadcast frame to an anti-port identifier matching the port identifier; And And controlling downlink transmission by multiplexing the configured broadcast frame. The method of claim 7, wherein And allocating the port identifier and the antiport identifier to the optical subscriber device. The method of claim 9, wherein assigning the port identifier and the antiport identifier comprises: Assign an antiport identifier according to the number of optical subscriber units, And registering an antiport identifier other than the antiport identifier assigned to a specific optical subscriber device among the assigned antiport identifiers in the specific optical subscriber device. In the information storage medium recording the data structure of the optical fiber termination device for the passive optical subscriber network, Port identifier information allocated for each optical subscriber device to transmit the broadcast frame to the optical subscriber device that has transmitted the broadcast frame to the optical line terminal; And The optical subscriber apparatus which has transmitted the broadcast frame to the optical line terminal includes the anti-port identifier information allocated to each optical subscriber apparatus so that the broadcast frame is not retransmitted. Information storage medium.

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