KR100689483B1 - Ethernet passive optical network and l2 switching method - Google Patents

Abstract

According to the present invention, an Ethernet passive optical fiber (OLT) including an L2 switch and an Ethernet passive optical fiber connected to the OLT and including a plurality of optical network units (ONUs) each including at least one service port or a subscriber port are included. The L2 switching method of a subscriber network includes: assigning predetermined PHY IDs to at least one service port or a subscriber port connected to each ONU; Tagging / filtering the PHY ID in the transmission frame using the PHY ID tagging / detagging layer; And transmitting an Ethernet frame destined for the predetermined port connected to the ONU through the port of the L2 switch assigned to the port when the Ethernet frame is received by the OLT.

Ethernet, Passive Optical Subscriber Network, Switch

Description

ETHERNET PASSIVE OPTICAL NETWORK AND L2 SWITCHING METHOD}             

1 is a view showing the configuration of an Ethernet passive optical subscriber network according to the prior art,

2 is a view showing the structure of an Ethernet standard frame;

3A is a diagram showing the structure of a tag Ethernet MAC frame according to a first embodiment of the present invention;

3b is a view showing the structure of a tag Ethernet MAC frame according to a second embodiment of the present invention;

4 is a diagram illustrating a detailed configuration of a PHY ID field shown in FIG. 3A;

5 is a view for explaining a peer-to-peer communication procedure of an Ethernet passive optical subscriber network according to a preferred embodiment of the present invention.

The present invention relates to an optical network, and more particularly, to an Ethernet passive optical subscriber network.

Passive optical subscriber network is a subscriber network structure that forms a distributed topology of tree structure by connecting multiple optical network units (ONU) to one optical line termination (OLT) using 1 × N optical distribution network (ODN). . Recently, the International Telecommunication Union-Telecommunication sect (ITU-T) has standardized the ITU-T G.982, ITU-T G.983.1, and ITU-T G. standards for Asynchronous Transfer Mode-Passive Optical Network (ATM-PON) systems. Documented as 983.3. In addition, the IEEE 802.3ah TF defined by the Institute of Electrical and Electronics Engineers (IEEE) is in the process of standardizing a passive optical subscriber network system based on Gigabit Ethernet.

Transmission capacity in ATM-PON and Ethernet passive optical subscriber network systems, as discussed in standard organizations such as ITU-T and IEEE 802.3, depends on the format of the data carried on two different wavelengths between the OLT and the ONU. In other words, the downlink transmission from the OLT at the telephone station to the subscriber ONU is carried by transmitting an ATM cell or Ethernet frame on a signal of 1550 nm (or 1490 nm) wavelength. Uplink transmission to the telephone-side OLT is discussed in the international organizations ITU-T and IEEE 802.3 on how to transmit data on 1310 nm wavelength signals.

In addition, point-to-point Gigabit Ethernet and ATM-PON MAC technologies have already been standardized, and their contents are described in IEEE 802.3z and ITU-T G.983.1. In addition, US Patent No. 5,978,374, which was invented by Gigad Ghaib et al. And issued a patent on November 2, 1999, discloses the MAC technology in ATM-PON in detail. have.

1 is a view showing the configuration of an Ethernet passive optical subscriber network according to the prior art, Figure 2 is a view showing the structure of an Ethernet standard frame. The Ethernet passive optical subscriber network includes an optical line terminal (OLT) 110, an optical network unit 120 (ODN), and a plurality of optical network units 132, 134, and 136 (ONU).

The OLT 110 accesses data of each ONU 132, 134, or 136 in a time division multiplexing (TDM) manner. The OLT 110 includes a Layer 2 switch and an L2 switch, and transmits a frame received by each ONU 132, 134, or 136 by matching an address and a port. In order to recognize the address, an address learning procedure is required. The medium access control (MAC) address learning of the ONU 132, 134, or 136 is initialized. While storing the Source Address (SA) in a predetermined table, the address assigned to each port is learned. At this time, the source address or destination address (Destination Address, DA) uses the MAC address of the ONU (132, 134 or 136) port. After the learning process is completed, the L2 switch receiving the frame transmits the frame only to the ported destination address and uses a static filtering entry (IEEE 802.1d clause 7.9.1).

In the operation of the 802.1d L2 switch, in the case of the unlearned address that cannot find the destination address of the received frame in the address table, the frame is transmitted to all ports except the received port. If there is an address in the table but the port assigned to this address is the same as the received port, this frame is discarded.

That is, the L2 switch interprets the destination address and broadcasts it in the case of a specific code. If the port of the destination address and the source address are the same, the frame is already assigned to the port by the concept of "broadcast and select" due to the characteristics of Ethernet. Since the connected end user 142 has received all the received frames, the received frames are discarded under the principle that they do not need to be delivered again.

However, as described above, in the conventional passive optical subscriber network, frames sent from one ONU to another ONU connected to the same passive optical subscriber network are not transmitted to all ONUs but transmitted only to the OLT. Therefore, frames to be transmitted upstream and downlink through the same port cannot be transmitted because they are discarded by the L2 switch table because the ports assigned to the destination address and the source address are the same. In this structure, there is a problem in that communication is not possible between ONUs in L2. This also applies to multi-subscribers or multi-services connected to one ONU, so that communication support is impossible when multiple LANs or types of services are classified and transmitted for one ONU.

Therefore, incompatibility between the Ethernet passive optical subscriber network and the L2 switch may be caused, and how to retransmit frames to the same port in the L2 switch of the OLT may be a big issue. For this reason, there is a need for a switching scheme compatible with existing L2 switches while supporting subscriber-to-subscriber communication or multi-service in an Ethernet passive optical subscriber network.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to overcome the incompatibility of the L2 switch in the Ethernet passive optical subscriber network, subscriber-to- subscriber communication or multi-subscription in the Ethernet passive optical subscriber network structure The present invention provides an L2 switching scheme capable of supporting multiple services and a quality of service (QoS), an Ethernet frame structure for implementing the same, and an Ethernet passive optical subscriber network and an L2 switching method using the same.

In order to achieve the above object, in accordance with the present invention, an optical line termination (OLT) including an L2 switch and a plurality of optical network units (ONUs), each of which includes at least one service port or subscriber port, are connected to the OLT. L2 switching method of the Ethernet passive optical subscriber network configured to include,

Assigning a predetermined PHY ID to each of at least one service port or subscriber port connected to each ONU;

Tagging / filtering the PHY ID in the transmission frame using the PHY ID tagging / detagging layer;

And when the Ethernet frame destined for the predetermined port connected to the ONU is received by the OLT, transmitting through the port of the L2 switch assigned to the port.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention; In describing the present invention, detailed descriptions of related well-known functions or configurations are omitted in order not to obscure the subject matter of the present invention.

3A is a diagram illustrating a structure of a tag Ethernet MAC frame according to a first embodiment of the present invention. The frame includes a destination address (DA) field 210, a source address (SA) field 220, a type field 230, a PHY ID field 240, and a message field 250. ) And a frame check (FCS) field 260.

In the case of a conventional Ethernet frame, the DA field 210 has a length of 6 bytes, the SA field 220 has 6 bytes, and the type field 230 has a length of 2 bytes. 240 is inserted using a tagging method when transmitting downlink from the OLT to the ONU or transmitting upward from the ONU to the OLT. The PHY ID is a unique ID assigned to each of at least one service port or subscriber port connected to each ONU. The PHY ID is divided to allocate a predetermined port to the L2 switch of the OLT and is assigned to each port of the L2 switch of the OLT. Mapped. The PHY ID field 240 is inserted into or removed from a PHY ID (PON) tagging / detagging layer and transmitted. The classification of the tag Ethernet MAC frame is possible by complexly defining the type field 230 to indicate whether or not the tag Ethernet MAC frame is simultaneously with the previously defined Ethernet frame.

3B is a diagram illustrating the structure of a tag Ethernet MAC frame according to a second embodiment of the present invention. The frame includes a DA field 310, an SA field 320, a first type field 330, a PHY ID field 340, a second type field 350, a message field 360, It consists of an FCS field 370. The first type field 330 is a field indicating whether or not it is a PHY ID tag Ethernet MAC frame, the second type field 350 is a previously defined Ethernet frame type field, and the frame structure is a second type field 350. Is identical to the structure of the frame shown in FIG.

In the case of FIG. 3A, the compatibility with the existing Ethernet frame is weak because the type field 230 should be switched to one of the previously defined Ethernet frame types while the PHY ID is de-tagged to be transferred to the upper layer. In this case, since the first type field 330 and the PHY ID are de-tagged together with the PHY ID, the tag is transmitted to the upper layer, and thus the compatibility with the existing system is large.

4 is a diagram illustrating an embodiment of a structure that the PHY ID field 240 shown in FIG. 3A may have. The PHY ID field 240 is composed of a 3-bit class 242, a 1-bit mode 244, and a 12-bit PHY ID 246 when defined as 2 bytes.

The PHY ID 246 corresponds to a unique number assigned when a new ONU or subscriber port or classified service port is registered.

The class 242 represents classes classified according to service level agreements (SLAs) of subscribers or types of multi-services supported. Priority may be given according to the class 242. The priority is given to the queue of the corresponding port of the L2 switch of the OLT, or the highest priority is given to the corresponding port of the ONU when the bandwidth is granted, thereby supporting QoS (Multiple Service). of Service) can be guaranteed. It can also be classified according to the class of SLA for the subscriber.

The mode 242 distinguishes between a point-to-point link mode (P) and a point-to-multipoint broadcast mode (B) for a transmission frame. In case of B mode, it is directly connected to the L3 router (Layer 3 router) instead of passing through the L2 switch port.

5 is a view for explaining the L2 switching operation of the Ethernet passive optical subscriber network according to an embodiment of the present invention. The Ethernet passive optical subscriber network is composed of one OLT 410 and a plurality of ONUs 450, 510, and 550 connected in a tree structure.

The ONU 450, 510 or 550 has one or more service ports or subscriber ports S1, S2, S3, S4, S5, S6, S7, S8 and S9 in addition to the connection ports to the OLT 410, respectively. . To assign a predetermined port to the L2 switch 440 of the OLT 410 for the one or more service ports or subscriber ports S1, S2, S3, S4, S5, S6, S7, S8, S9, respectively. Give a predetermined PHY ID. This can be done during the initial registration process. The OLT 410 assigns a PHY ID when a new ONU or subscriber port or a classified service port is registered. When the ONU or subscriber / service port is deregistered and remains as a cold ONU or port, the PHY ID that was assigned is released and released by another new ONU or subscriber / service port. You can reuse the PHY ID.

The assigned PHY ID is mapped to each port of the L2 switch 440 of the OLT 410 by demultiplexing a logical link to allocate a predetermined port to the L2 switch 440 of the OLT 410. Lose.

In the case of uplink transmission from the ONU 450, 510, 550 to the OLT 410, the PHY ID tagging / detagging layer 455, 515, 555 of the ONU 450, 510, 550 is an LLC layer 480, A tagging frame type is set in an Ethernet frame generated from 540 and 580, and a tag is transmitted by tagging its PHY ID. Thereafter, the Ethernet frame is transmitted upward to the OLT 410 through the PHY layers 475, 535, 575, etc. The PHY ID tagging / detagging layer 435 of the OLT 410 receives the PHY ID of the received frame. After checking, de-tagging and simultaneously demultiplexing the link to the corresponding port of the L2 switch 440 and transmits to the corresponding L2 switch port. The L2 switch 440 sees the DA through the address learning process and switches the frame to the corresponding port to output the DA.

The output frame is transmitted downward from the OLT 410 to the corresponding ONUs 450, 510, and 550. In this case, the PHY ID tagging / detagging layer 435 of the OLT 410 sets a tagging frame type and outputs the output frame. The PHY ID corresponding to the port of the L2 switch 440 is tagged and transmitted downward to the corresponding ONU (450, 510, 550). The PHY ID tagging / detagging layer (455, 515, 555) of the ONU (450, 510, 550) receiving this checks the tagging frame type and detags the PHY ID while matching the received PHY ID with its own PHY ID. If so, it transmits to the upper layer to the subscriber or the service port (S1, S2, S3, S4, S5, S6, S7, S8, S9). If it does not match, the frame is discarded.

If the frame to be transmitted is used for broadcasting, the mode 242 of FIG. 4 can be seen. In the case of the point-to-multipoint broadcast mode (B), the PHY ID tagging / detagging layer 435 of the OLT 410 is used. After multiplexing the logical link in the UE, it is sent directly to the L3 router (Layer 3 router) instead of through the L2 switch port and then routed back to the OLT 410, where the PHY ID tagging / detagging layer 435 broadcasts. Default PHY ID or PHY ID of the OLT 410 designated for use is tagged and transmitted downward. This downlink transmission frame is received by all ONUs 450, 510, and 550. The PHY ID tagging / detagging layer 455, 515, and 555 of the ONUs 450, 510, and 550 view the mode and indicate that the frame is a broadcast frame. After the PHY ID does not match with its own PHY ID, it decodes the PHY ID and transmits it to the upper layer. In broadcast mode (B), the reason why the frame is sent directly to the L3 router (Layer 3 router) instead of through the L2 switch port is because the frame is transmitted to all ports except the input port through the L2 switch port. This is to prevent such multiple broadcasts because there are duplicate broadcasts for the number of ports-1).

Checking whether the transmission frame is a tag control frame is performed by performing a function of identifying a layer other than the MAC control layer (465, 525, and 565) in addition to the type field for the tag frame. It is also possible to transfer up to layers 465, 525, 565.

As shown in FIG. 4, a class for a transmission frame may be assigned to a PHY ID, and priority may be given accordingly. ONU may be given priority to a queue of a corresponding port of an L2 switch 440 of the OLT 410 or a band is assigned. By providing the highest priority to the corresponding port of 450, 510, and 550, it is possible to guarantee QoS in multi-service support. It can also be classified according to the class of SLA for the subscriber.

As described above, the Ethernet passive optical subscriber network according to the present invention overcomes the incompatibility of the existing L2 switch and proposes an L2 switching scheme capable of supporting subscriber-to-subscriber communication or multi-service, thereby providing not only ONU vs. ONU in L2. Enable subscriber to subscriber communication. In addition, by providing a PHY ID according to the type of service, a point-to-point emulation technique for such a service port may be implemented to support multi-service. In addition, the class of the class can be specified according to the subscriber's SLA or the type of the multi-service to be supported. The priority is given according to the class, which has the advantage of guaranteeing QoS or charging according to the SLA when supporting the multi-service.

Claims (7)

In an Ethernet passive optical subscriber network comprising an optical line termination (OLT) having an L2 switch and a plurality of optical network units (ONUs) connected to the OLT and each having at least one service port or subscriber port. , The frame transmitted between the OLT and ONU, A DA field indicating a destination address; An SA field indicating a source address; And a PHY ID field indicating a PHY ID which is a unique number assigned to a service port or a subscriber port of the ONU, And the OLT transmits through a port of the L2 switch assigned to the service port or the subscriber port when receiving the frame destined for the service port or the subscriber port of the ONU. The method of claim 1, The PHY ID field is A PHY ID corresponding to a unique number assigned to a service port or a subscriber port of the ONU; A class representing classes classified according to types of services supported; Ethernet passive optical subscriber network comprising a mode for distinguishing between point-to-point link mode and point-to-multipoint broadcast mode. Optical Line Termination (OLT) having an L2 switch and L2 of an Ethernet passive optical subscriber network connected to the OLT and including a plurality of optical network units (ONUs) each having at least one service port or subscriber port. In the switching method,  Assigning a PHY ID to a service port or a subscriber port of each ONU;  Tagging / filtering the PHY ID in the transmission frame using the PHY ID tagging / detagging layer; When the Ethernet frame destined for the service port or the subscriber port of the ONU is received by the OLT, transmitting through the port of the L2 switch assigned to the service port or the subscriber port. L2 switching method of optical subscriber network. The method of claim 3, And assigning a class to a service port or a subscriber port of the ONU, thereby performing transmission processing according to priority. The method of claim 3, The L2 switching method of an Ethernet passive optical subscriber network, further comprising the step of distinguishing the transmission signal for peer-to-peer communication and the broadcast signal by assigning a mode of the transmission frame. The method of claim 3, wherein the frame, A DA field indicating a destination address; An SA field indicating a source address; A type field indicating a type of the frame; And a PHY ID field indicating a PHY ID which is a unique number assigned to a service port or a subscriber port of the ONU. The method of claim 6, wherein the PHY ID field, A PHY ID corresponding to a unique number assigned to a service port or a subscriber port of the ONU; A class representing classes classified according to types of services or subscribers supported; A L2 switching method of an Ethernet passive optical subscriber network comprising a mode for distinguishing a point-to-point link mode and a point-to-multipoint broadcast mode.

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