KR100535256B1 - communication system for peer-to-peer communication between Optical network units on Ethernet-based Passive Optical Network and communication method thereof - Google Patents

Abstract

The present invention relates to a communication system having a hierarchical structure for supporting peer-to-peer communication between optical network units (ONUs) in an Ethernet-based passive optical network (PON) network, and a communication method thereof.

To this end, the ONU inserts a PON-tag into an existing Ethernet preamble, creates and manages an address table in the emulation layer of the OLT, and records the PON-tag and MAC address in the address table. In the Frame Reflecting & Multiplexing (FRM) layer on the MAC control layer, it is determined whether to forward the Ethernet frame entering the OLT port to the upper side or the ONU by referring to the mirror address table and the upper address table of the address table. The upper address table is created and managed by FRM. The frame dropped from the FRM layer is transmitted by attaching a PON-tag corresponding to a source address or by attaching a broadcast PON-tag to the preamble with reference to the address table in the emulation layer.

Accordingly, it is possible to support peer-to-peer communication between ONUs while using the existing Ethernet protocol in an Ethernet-based PON network.

Description

Communication system for peer-to-peer communication between Optical network units on Ethernet-based Passive Optical Network and communication method

The present invention provides an optical line termination (OLT) for supporting peer-to-peer communication between optical network units (ONUs) in an Ethernet-based passive optical network (PON) (hereinafter referred to as EPON). It relates to a hierarchy and a communication method.

In the existing Ethernet, all terminals or nodes belonging to the same LAN segment simultaneously receive the same frame. However, in a PON network, if an attempt is made to send a frame from an ONU to another ONU, the ONU transmits the frame to the OLT and the OLT retransmits the frame. Look at the destination address and send it back to the corresponding ONU. However, according to existing Ethernet standards, frames received by OLT cannot be sent back to ONU. The following proposals have been made to solve this problem in the EPON network.

The first way is to put an emulation layer for peer-to-peer communication between the PHY (physical) layer and the MAC layer. This method is further divided into two ways. One is to remove the PON-tags (hereinafter referred to as PON-tags) of all frames received from the ONU in the emulation layer and upload them to the upper layer, and simultaneously copy these frames and broadcast them to all ONUs via the PON interface. . The ONU checks the PON-tag of the received frame and filters the dropped PON-tag and discards the frame. Otherwise, the ONU removes the PON-tag and sends it to the upper level. However, this method sends back all frames to the PON interface even in the case of non-peer-to-peer communication between ONUs.

Another way is to look at the PON-tags attached to the frames from each ONU, identify the frames and send them to the upper MAC layer. The upper MAC layer is composed of as many logical MAC layers as there are ONUs connected to the PON interface, and each MAC layer is connected to a port of a bridge so that frames are switched through the bridge and descend through the corresponding MAC layer. The frames that are switched down from the bridge are broadcasted to the ONU via the PON interface with a PON-tag corresponding to the destination address. The ONU checks the PON-tag of the received frame and, if it is its own PON-tag, removes the PON-tag and uploads it to the upper level. Otherwise, it filters and discards the frame. In this case, since frame multiplexing is performed at each MAC layer, and multiplexing between MAC layers must be performed once again, there is a disadvantage in that the frame multiplexing is complicated, and the logical MAC layer for one PON interface is configured by the number of ONUs. There are disadvantages that must be made.

The second method is to place a Shared LAN Emulation function above the OLT MAC layer. Shared LAN emulation consists of three parts: Lower Layer Shared LAN Emulation, Logical MAC, and Upper Layer Shared LAN Emulation (ULSLE). The lower layer shared LAN emulation function looks at the LLID (Logical Link ID) of the frame from the ONU and passes it to the corresponding logical MAC. The logical MAC passes this frame to higher layer shared LAN emulation. The upper layer shared LAN emulation has a function similar to that of IEEE802.1D, and can determine the LLID of a frame and send it down to a corresponding logical MAC for peer-to-peer communication. In the logical MAC, the LLID is set in this frame and sent down to the lower layer. In case of broadcasting, it is sent down through a separate broadcasting logical MAC. In this case, the broadcast bit is set. At this time, there are k logical MACs (number of LLIDs x 2 + 1), and the frame type needs to be changed unlike the standard for the shared LAN emulation function. The proposal of this technique does not mention the exact frame shape. In addition, since multiplexing between logical MACs is required, the multiplexing of overall downlink data is complicated.

Therefore, an object of the present invention is to support peer-to-peer communication between ONUs in an EPON network.

In particular, the technical problem to be achieved by the present invention is to enable peer-to-peer communication between ONUs while minimizing changes to existing Ethernet standards, and to simplify the hierarchical structure.

According to an aspect of the present invention, a communication system supporting peer-to-peer communication between ONUs in an Ethernet-based PON network includes a PON-tag in a frame-preamble transmitted from the OLT. Including an attached frame--the physical layer receiving the frame; And a data link layer including an emulation layer, a MAC layer, a MAC control layer, and a MAC emulation layer that processes frames received through the physical layer, wherein the data link layer is located between the emulation layer and the MAC layer. A P2PE layer configured to generate and manage an address table and a mirror address table thereof matching a PON-tag and a source address of a frame received from the ONU; A Frame Reflecting & Multiplexing (FRM) layer located between the MAC control layer and the MAC emulation layer to perform up-processing for transmitting to a broadcast or higher layer according to a destination address of the frame, and down-processing of frame transmission to a lower layer. It includes more.

Here, the P2PE layer includes a frame receiving unit which receives a first frame transmitted from the physical layer; An address table processor for generating an address table matching the PON-tag and the destination address of the received first frame and a mirror address table thereof; A frame processor for transmitting the first frame to an upper layer; A search unit for receiving a second frame transmitted from the upper layer and searching the address table to find a PON-tag corresponding to a destination address of the second frame; And a PON-tag processor for attaching the PON-tag corresponding to the destination address to the preamble of the second frame and transmitting the PON-tag to the physical layer.

The FRM layer may further include: an address determination unit configured to generate and manage an upper address table and to determine a destination address of a first frame input based on the mirror address table and the upper address table; And an uplink frame processor for forwarding the first frame to the upper side, reflecting or broadcasting to the ONU according to the address determination result.

Herein, if the destination address of the first frame is an address outside the EPON network, the uplink frame processor uploads the first frame to an upper bridge, and the destination address of the first frame is included in the upper address table and the mirror address table. If no or broadcast address, the first frame is broadcast in both upstream and ONU directions, and if the destination address of the first frame is in the mirror address table, the first frame is returned to the lower layer.

The FRM layer may further include a downlink frame processor that flags a destination address of a second frame transmitted from an upper layer in the address table, and the searcher only flags addresses of the downlink frame processor in the address table. The PON-tag corresponding to the destination address of the downlink frame is found and provided to the PON-tag processor.

If the destination address of the second frame is not in the address table, the PON-tag processing unit attaches the broadcast PON-tag to the preamble of the second frame and delivers it to the physical layer.

In a communication system having this feature, the FRM layer performs a multiplexing function between a second frame descending from the upper layer and a frame reflected in the FRM.

According to another aspect of the present invention, there is provided a communication method comprising: a) a communication method of a system supporting peer-to-peer communication between ONUs in an Ethernet-based PON network, the method comprising: a) receiving a first frame transmitted from the ONU; b) generating an address table and a mirror address table thereof matching the PON-tag and the source address of the received first frame; c) generating and managing an upper address table and determining an address of a first frame input based on the mirror address table and the upper address table; And d) forwarding the first frame upward, reflecting or broadcasting to the ONU according to the address determination result.

In addition, e) receiving a second frame transmitted from a higher layer, searching the address table to find a PON-tag corresponding to a destination address of the second frame; And f) attaching the PON-tag corresponding to the destination address to the preamble of the second frame and forwarding the same to the physical layer.

Here, step d) includes: if the destination address of the first frame is an address outside the EPON network, uploading the first frame to an upper bridge; If the destination address of the first frame is not in the upper address table and the mirror address table or is a broadcast address, broadcasting the first frame in both upper and ONU directions; And if the destination address of the first frame is in the mirror address table, returning the first frame to a lower layer.

Also, the step e) may include flagging the destination address of the second frame transmitted from the upper layer in the address table; And searching for only an address flagged in the address table to find a PON-tag corresponding to a destination address of a downlink frame.

In a communication method having such a feature, the system preferably has the same hierarchical structure as the communication system described above.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

The present invention supports retransmission in a port for frame transmission between ONUs existing in the same port not supported by the existing Ethernet bridge.

In general, the PON network is a medium-sharing tree structure. Unlike conventional media sharing in Ethernet, the downlink frame from the OLT to the ONU is transmitted to all ONUs, and the uplink frame transmitted from the ONU is different from the media and splitters. It has a direction of transmission that cannot be received in ONU but can only be received in OLT.

FIG. 1 shows a schematic structure of an Ethernet-based passive optical communication network, that is, EPON, according to an embodiment of the present invention, and FIG. 2 shows an EPON hierarchical structure.

The present invention provides peer-to-peer communication between ONUs in an EPON network. The EPON network is a PON network based on Ethernet. As shown in FIG. 1, the EPON network includes an optical line termination (OLT), an optical distribution network (ODN), and an optical network unit (ONU). In one EPON network, several ONUs are connected to one OLT through ODN. ODN consists of fiber and optical splitter.

Communication between ONUs is through OLT. In the existing Ethernet network, ONU and OLT are connected by peer-to-peer or shared bus. In the existing Ethernet network, frames transmitted by ONU are received by all ONUs and OLTs, so there is no problem in communication between ONUs.

However, in the EPON network, OLT and ONU are connected point-to-multipoint via ODN, and frames transmitted from OLT are broadcast to all ONUs due to the directionality of fiber and optical splitter, and frames transmitted from ONU are not received by other ONUs. , Only receives OLT. Therefore, in order to communicate between ONUs, OLT must send the frame received from the ONU to the corresponding ONU by looking at the destination address.

In Ethernet, frame relay is performed at the bridge. In IEEE802.1D, which defines the function of the bridge, when a frame is received, the received port cannot send the frame back.

Accordingly, the present invention provides a Frame Reflection & Multiplexing (FRM) function and a peer-to-peer emulation function in the RS layer to provide communication between ONUs in an EPON network while complying with the IEEE802.1D standard.

In order to provide such a function, the OLT according to an embodiment of the present invention has a hierarchical structure as follows.

As shown in FIG. 2, an OLT according to an embodiment of the present invention is composed of a physical layer and a data link layer.

The physical layer 11 is a physical layer in an Ethernet-based PON network, and may include a physical coding sublayer (PCS), a physical media attachment (PMA), a physical media dependent (PMD), and the like.

The data link layers 12 to 17 may include an emulation layer (RS) 12, a P2PE layer 13, a MAC layer 14, a MAC control layer 15, an FRM layer 16, and a MAC emulation layer ( 17).

The data link layer and the physical layer transmit and receive data through the Gigabit Media Independent Interface (GMII). GMII is an interface specification that performs interface functions capable of processing Ethernet frames of 1 gigabit and below.

The emulation layer 12 performs a cyclic redundancy check (CRC) check on the information included in the preamble on the frame raised from the physical layer 11. In particular, the PON-tag provided from the ONU provides the upper layer with a frame attached to the preamble.

The P2PE layer 13 looks at the frame received from the ONU, and generates and manages a lookup table of the PON-tag of the frame and the destination address, that is, the address table T1. It also creates and manages a mirror address table T2 of this address table.

The MAC layer 14 downwardly generates an FCS for the control frame for the MCP (Mult Point Control Protocol) among the Ethernet frames transmitted from the MAC control layer 15, inserts an IFG (Inter Frame Gap), and a MIB (for downlink frame). Management information base (Management Information Base) counter management and the like, and upwards has a frame check sequence (FCS) check, address filtering and management information base (MIB) counter management function for the uplink frame.

In the case of OLT, the MAC control layer 15 is a layer that performs bandwidth allocation functions and tasks related to scheduling and other MAC control.

The MAC layer 14 and the MAC control layer 15 are general system structures for the Ethernet PON, and their operation is defined in IEEE802.3, and thus detailed description thereof will be omitted.

Frames processed by the P2PE layer 13 are delivered to the FRM layer 16 through the upper MAC, MAC control layers 14,15.

The FRM layer 16 performs downlink processing such as upstreaming to a broadcast or higher bridge and forwarding frames to a lower layer according to a destination address of a frame. Also, it performs a multiplexing function between the downlink frame descended from the upper side and the frame reflected in the FRM.

Specifically, if the address is outside the EPON network, the frame is sent to the upper bridge. If the address is unknown or the address is unknown, the frame is broadcasted through the bridge and the PON interface. If the destination address is in the address table T1 generated in the P2PE layer 13, the frame is returned to the lower layer. It also provides multiplexing for downlink frames.

The MAC emulation layer 17 is similar to the MAC function, but provides functions mainly for uplink Ethernet frame matching, FCS check, PAUSE frame processing, etc., except for some management functions.

The bridge 30 communicates between ONUs in the PON system through the creation and management of filtering address tables for destination MAC addresses and VLAN (virtual LAN) IDs for each PON-tag, along with basic simple bridge functions related to EPON. VLAN Multicast is provided.

For convenience of explanation, the P2PE layer 13 and the emulation layer 12 are separated and the FRM layer 16 and the MAC emulation layer 17 are separated, but the P2PE layer 13 is included in the emulation layer 12. And the FRM layer 16 may be included in the MAC emulation layer 17.

Meanwhile, as shown in FIG. 2, the ONU includes a physical layer 21 and data link layers 22 to 25, and the data link layer has the same emulation layer 22, P2PE layer 23, and MAC as in the OLT. The layer 24 includes the MAC control layer 25 and, unlike the OLT, does not include the FRM layer.

In the hierarchical structure as described above, the P2PE layer 13 and the FRM layer, for providing inter-ONU communication in the EPON network, complying with the standard that when receiving a frame cannot receive the frame back to the received port. The operation between (16) and the structure of the hierarchy for performing the same will be described, and the structure thereof is shown in FIG.

As shown in FIG. 3, the P2PE layer 13 includes a frame receiving unit 131 for receiving a frame transmitted from a lower layer, a PON-tag attached to a preamble of the received frame, an address table T1 of a source address, and An address table processing unit 132 for generating and managing a mirror address table T2 thereof, and a frame processing unit 133 for delivering a frame to an upstream layer, and a retrieval unit 134 for processing a downlink frame transmitted from an upper layer. ) And a PON-tag processing unit 135.

Meanwhile, the FRM layer 16 receives an uplink frame addressed at the P2PE layer 13 to determine a corresponding destination address, and an uplink frame processor for broadcasting or transmitting a frame according to the determined address. 162, and a downlink frame processor 163 which flags an address for a downlink frame transmitted from the upper MAC emulation layer 17.

4 and 5 illustrate operating states based on the structure of these P2PE and FRM layers 13 and 16.

For example, in the ONU, the PON-tag allocated from the OLT in the P2PE layer 13 is attached to the preamble of the frame, and the frame is transmitted to the OLT. The frame to which the PON tag is attached is transmitted to the data link layer through the physical layer 11 of the OLT.

Then, as shown in FIG. 4, the frame receiving unit 131 of the P2PE layer 13 receives the frame transmitted from the physical layer, and the address table processing unit 132 is a check table of the PON-tag of the frame and the destination address. An address table T1 is generated, and at the same time, a mirror address table T2 of this address table T1 is generated.

Here, the address table T1 is an address table of MAC addresses for the terminals on the ONU side connected to the PON interface. The OLT can know which terminals are connected to the PON interface based on the address table T1. When generating the address table T1, the OLT looks at the SAs (Source Address) of the frames received from the PON interface and updates the address table T1 in the case of a new SA. The mirror address table T2 is a copy of the contents of the address table T1 as it is, and since the mirror address table T2 copies the address table T1 when the address table T1 is updated, T2) is also updated. This address table T1 is generated in the P2PE layer 13, which is copied to the mirror address table T2, and in the FRM layer 16 only the mirror address table T2 can be read.

Meanwhile, the frame processor 133 transmits the received frame to the FRM layer 16 via the upper MAC and MAC control layers 14 and 15.

When the Ethernet frame entering the OLT port is forwarded, the address determination unit 161 of the FRM layer 16 forwards to the upper position with reference to the mirror address table T2 of the address table T1 generated in the P2PE layer 13. Decide if you want to reflect it or towards the ONU. At this time, the address table (upper address table) for the higher level is generated and managed by the FRM layer 16. The address determining unit 161 provides the determination result to the uplink frame processing unit 162.

The upper address table is generated based on the SAs of the frames received at the opposite network interface instead of the PON interface. The FRM layer 16 generates this upper address table and determines the forwarding direction by looking at the upper address table and the mirror address table when determining the forwarding. Specifically, when the Ethernet frame is received from the PON interface, the address determining unit 161 reads the destination address of the received frame first and then compares it with the addresses of the mirror address table and the upper address table.

As shown in FIG. 5, if the destination address of the received frame is an address outside the EPON network, the uplink frame processor 162 uploads the received frame to the upper bridge, and if the address is a broadcast address or an unknown address. Broadcast over the bridge and PON interface. That is, if one of the addresses in the mirror address table T2 and the destination address of the received frame match, the received frame is returned to the lower layer to be reflected in the ONU direction. Also, if none of the addresses in the mirror address table T2 match the destination address of the received frame, and one of the addresses in the upper address table matches the destination address of the received frame (the destination address of the received frame is In case of address outside EPON network) Forward received frame to upper level. In addition, if none of the addresses in the mirror address table T2 and the upper address table match the destination address of the received frame or the destination address is the broadcast address, the received frame is forwarded to the upper side and simultaneously reflected (or broadcasted) to the ONU (or broadcast). do).

On the other hand, when a downlink frame transmitted through the MAC emulation layer 17 is received, the downlink frame processor 163 of the FRM layer 16 of the address table generated and managed in the P2PE layer 13 for the downlink frame down in the ONU direction Flag the corresponding address (destination address) and forward the downlink frame to the lower layer.

Then, if the downlink frame is delivered to the P2PE layer 13 through the MAC control layer 15 and the MAC layer 14, the search unit 134 of the P2PE layer 13 only the addresses flagged by the FRM layer 16. The PON-tag corresponding to the destination address of the downlink frame is found and provided to the PON-tag processor 135. At this time, fast address search is performed by the flag function of the FRM.

Accordingly, the PON-tag processing unit 135 attaches the PON-tag corresponding to the destination address to the preamble of the downlink frame and transmits it to the lower layer. For example, a frame taken down from the FRM layer 16 is transmitted with a PON-tag corresponding to a source address or a broadcast PON-tag attached to the preamble with reference to the address table T1. In this case, if the frame is a frame raised from the ONU, if the frame is reflected from the FRM layer 16, the destination address is included in the address table. Therefore, the corresponding PON-tag is added. The broadcast PON-tag is attached.

As a result, the ONU filters the frames received from the OLT by looking at the PON-tag in the P2PE layer 13. If the PON-tag of the received frame is its own or broadcast, the ONU removes the PON-tag of the preamble and uploads it to the upper MAC layer. If it is not its PON-tag, the ONU filters and discards the frame.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

According to the embodiment of the present invention, it is possible to support peer-to-peer communication between ONUs while using the existing Ethernet protocol in the Ethernet-based PON network.

In addition, since only the frame is sent to the PON link through the address table, the efficiency of the link can be improved, and the search time can be reduced by searching the corresponding PON-tag only for the flagged addresses using flags when searching for an address.

In addition, many changes in the Ethernet standard reduce compatibility with existing Ethernet networks, and complex structures increase the difficulty of implementation, but according to the present invention, without having multiple logical MACs, one MAC can be used like an existing Ethernet. This exists and does not change the hierarchical structure below the MAC layer.

It also maintains compatibility with Ethernet networks without changing the form of Ethernet frames, and simplifies the function of the emulation block to support peer-to-peer. In addition, address tables for peer-to-peer communication can be created and managed efficiently, and address tables can be searched quickly.

1 is a schematic structural diagram of an EPON according to an embodiment of the present invention.

2 is an EPON hierarchical structure diagram according to an embodiment of the present invention.

3 is a structural diagram of P2PE and Frame Reflection & Multiplexing (FRM) according to an embodiment of the present invention.

4 and 5 are exemplary views illustrating the operation of the P2PE and FRM layer according to an embodiment of the present invention.

Claims (11)

In a communication system supporting peer-to-peer communication between optical network units (ONUs) in an Ethernet-based passive optical network (PON) network A physical layer that receives a frame transmitted from the OLT, including a frame having a PON tag attached to a preamble; And Data link layer including an emulation layer, a MAC layer, a MAC control layer, and a MAC emulation layer to process frames received through the physical layer Including; The data link layer is A P2PE layer, located between the emulation layer and the MAC layer, for generating and managing an address table and a mirror address table thereof matching a PON-tag and a source address of a frame received from the ONU; And Frame Reflecting & FRM located between the MAC control layer and the MAC emulation layer to perform upstream processing for broadcasting a frame or forwarding the frame to a higher layer and downlink processing for a lower layer according to a destination address of the frame. Multiplexing layer Communication system further comprising. The method of claim 1 The P2PE layer is A frame receiving unit receiving a first frame transmitted from the physical layer; An address table processor for generating an address table matching the PON-tag and the destination address of the received first frame and a mirror address table thereof; A frame processor for transmitting the first frame to an upper layer; A search unit for receiving a second frame transmitted from the upper layer and searching the address table to find a PON-tag corresponding to a destination address of the second frame; And PON-tag processing unit for attaching the PON-tag corresponding to the destination address to the preamble of the second frame to the physical layer Communication system comprising a. The method of claim 2 The FRM layer is An address determination unit configured to generate and manage an upper address table and to determine a destination address of a first frame input based on the mirror address table and the upper address table; And An uplink frame processor for forwarding the first frame to the upper side, reflecting to the ONU, or broadcasting according to the address determination result Communication system comprising a. The method of claim 3, The uplink frame processor If the destination address of the first frame is an address outside the EPON network, the first frame is uploaded to an upper bridge, If the destination address of the first frame is not in the upper address table and the mirror address table or is a broadcast address, the first frame is broadcast in both upper and ONU directions. And if the destination address of the first frame is in the mirror address table, return the first frame to a lower layer. The method according to claim 2 or 3 The FRM layer further includes a downlink frame processor that flags a destination address of a second frame transmitted from an upper layer in the address table. And the searcher searches only the addresses flagged by the downlink frame processor in the address table, finds a PON tag corresponding to a destination address of the downlink frame, and provides the PON tag to the PON-tag processor. The method of claim 5 And, if the destination address of the second frame is not in the address table, the PON-tag processor attaches a broadcast PON-tag to the preamble of the second frame and delivers the PON-tag to the physical layer. The method of claim 1 The FRM layer performs a multiplexing function between a second frame descended from the upper layer and a frame reflected in the FRM. A communication method of a system supporting peer-to-peer communication between ONUs in an Ethernet-based PON network a) receiving a first frame delivered from the ONU; b) generating an address table and a mirror address table thereof matching the PON-tag and the source address of the received first frame; c) generating and managing an upper address table and determining a destination address of a first frame input based on the mirror address table and the upper address table; And d) forwarding the first frame upward, reflecting or broadcasting to the ONU according to the address determination result; Communication method comprising a. The method of claim 8 e) receiving a second frame transmitted from an upper layer, searching the address table and finding a PON-tag corresponding to a destination address of the second frame; And f) attaching the PON-tag corresponding to the destination address to the preamble of the second frame and forwarding it to the physical layer Communication method further comprising. The method of claim 8 Step d) Uploading the first frame to an upper bridge if the destination address of the first frame is an address outside the EPON network; If the destination address of the first frame is not in the upper address table and the mirror address table or is a broadcast address, broadcasting the first frame in both upper and ONU directions; And Returning the first frame to a lower layer if the destination address of the first frame is in the mirror address table Communication method comprising a. The method of claim 9 Step e) Flagging, in the address table, a destination address of a second frame transmitted from the upper layer; And Searching for only the address flagged in the address table to find a PON-tag corresponding to a destination address of a downlink frame; Communication method comprising a.