JP2011023846A - Line emulation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten time during which communication becomes impossible caused by a change in a communication path due to a maintenance work and occurrence of a fault in a line emulation device having redundant configuration of the communication path. <P>SOLUTION: Upon switching of physical ports used for the communication, a frame for updating an MAC (Media Access Control) address learning table for informing another connected device of a change in MAC address of itself is issued. The device which receives the frame for updating updates the learning table based on information on a transmission source MAC address in the frame, does not handle the frame for updating as a user frame, and immediately cancels the frame. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a circuit emulation apparatus that accommodates a non-Ethernet (registered trademark, hereinafter the same) line in an Ethernet network, and relates to an apparatus that performs frame transfer based on a MAC (Media Access Control) address that is a physical address unique to the apparatus. Is.

  Circuit emulation is widely known as a technique for accommodating a dedicated line service for communication between bases represented by ATM (Asynchronous Transfer Mode) and TDM (Time Division Multiplexing) in an economical Ethernet communication network.

  This is a method for artificially connecting lines of a communication method different from circuit emulation (for example, Non-Patent Document 1). FIG. 3 shows an example of a network system configuration using circuit emulation. The network system configuration example shown in FIG. 3 includes an Ethernet network 301, circuit emulation devices 302 and 303, non-Ethernet network transmission devices 304 and 305, and non-Ethernet network terminals 306 and 307. The communication emulation between the networks can be mutually converted by the circuit emulation devices 302 and 303, and the Ethernet network 301 can be used to accommodate the non-Ethernet network.

  Point-to-point communication between sites is performed by setting up a VLAN (Virtual Local Area Network) on the Ethernet network and dividing the broadcast domain in order to provide dedicated line services for communication between sites using the Ethernet network. Realized.

Metro Ethernet Forum, "Implementation Agreement for the Emulation of PDH Circuit over Metro Ethernet Networks", (US), October 2004

  FIG. 2 shows a network configuration example using a circuit emulation device and an Ethernet network. In FIG. 2, circuit emulation apparatuses 201, 202, 203, and 204 are respectively connected to physical ports A1, B1, A2, B2, A3, B3, A4, and B4 connected to the Ethernet network and physical ports C1, C2, and the like connected to the non-Ethernet network. C3 and C4. Non-Ethernet network terminals 211, 212, 213, and 214 are connected to physical ports connected to the non-Ethernet network, and layer 2 switches 221, 222, 223, and 224 are connected to physical ports connected to the Ethernet network. Since a dedicated line service using an Ethernet network requires highly reliable communication, there may be a redundant (redundant) configuration of communication paths and physical ports as shown in the figure. In the figure, Ethernet network connection ports A1 and B1, A2 and B2, A3 and B3, and A4 and B4 of the circuit emulation apparatus are duplexed. One of the duplicated physical ports operates as the active system and the other as the standby system. The standby port is blocked and frame transmission / reception is performed only by the active system. When a failure occurs in the communication path, the operating physical port, or the hardware to which the port belongs, it is automatically switched to the standby physical port to maintain communication. If the physical port needs to be switched due to maintenance work or the like, it can also be switched manually. Each of the physical ports A1, B1, A2, B2, A3, B3, A4, and B4 has an independent MAC address, and here, it is assumed that a MAC address having the same name as the physical port name is set (example: physical The MAC address of port A1 is A1). Layer 2 switches 221, 222, 223, and 224 are connected in a loop so that they have a redundant configuration. When a failure occurs in a communication route or a layer 2 switch, the communication is maintained by switching to a route without a failure. Do. In order to prevent a logical loop, a Spanning Tree Protocol (hereinafter referred to as STP) standardized by IEEE802.1d is used. STP prevents logical loops by blocking specific ports. Blocked ports do not send or receive frames. Here, it is assumed that the port P22 of the layer 2 switch 222 is blocked by the STP.

  A VLAN for performing Point to Point communication is set between the circuit emulation devices. Broadcast domains are divided by setting individual VLANs for each connection device. VLAN is managed by VLANID. A port belonging to the layer 2 switch is set for each VLAN ID, and a broadcast frame flows only in this port. A VLAN ID 232 (affiliated ports: P11, P12, P13, P21, P22, P23, P31, P32, P34, P41, P42, P44) is set between the line emulation apparatuses 201 and 202. The VLANID 233 (affiliated ports: P11, P12, P13, P21, P22, P23, P31, P32, P33, P41, P42, P45) is set between them, and the VLANID 234 (affiliated port) is set between the line emulation apparatuses 201 and 204. : P11, P12, P13, P21, P22, P23, P31, P32, P35, P41, P42, P43) are set.

  Point-to-point communication between circuit emulation devices is possible even when a broadcast frame is used by applying VLAN. For example, in the communication from the circuit emulation devices 201 to 202, the network has a redundant configuration as described above. Therefore, in addition to the signal route necessary for the original communication (route that is output from the physical port A1 and reaches the physical port A2 via the ports P11, P13, P41, and P44 of the layer 2 switch), other affiliations of the VLANID 232 A frame also flows to ports P12, P21, P23, P31, P32, P34, and P42 (P22 is not used because it is a blocking port by STP). This frame is a frame that flows through a redundant path and does not directly contribute to normal communication.

  In communication from the circuit emulation device 201 to 204, a signal path necessary for communication (output from the physical port A1 and reaches the physical port B4 via the ports P11, P13, P41, P42, P32, and P35 of the layer 2 switch. The frame (the frame flowing from the port P42 of the layer 2 switch to the port P32) exists on the same route as that of the route emulation device 201 to 202 on the same route. By using the broadcast frame in this way, unnecessary traffic flowing through the redundant path causes a band to be used for original communication.

  Therefore, a MAC address learning function is added to the circuit emulation device in order to reduce unnecessary traffic flowing through the redundant path as described above, and frames are transmitted and received by unicast. FIG. 4 shows a database of the MAC address learning table in the circuit emulation device 201. The correspondence relationship between the transmission source MAC address of the frame received from another device and the VLANID is stored in the MAC address learning table in the device. The destination MAC address is specified when performing unicast communication using this database. When the MAC address is not learned, a broadcast address is assigned to the destination MAC address, and the frame is transmitted by broadcast. Also, an aging timer is set in the learning table, the non-communication time with the accommodated VLAN is counted, and when the time set in the aging timer (for example, 300 seconds) expires, the corresponding stored information is deleted. When a frame from another source MAC address is received before the aging time of the accommodated VLAN expires, the learning table is overwritten and updated with the source MAC address of the frame received later.

  In the above configuration, when the circuit emulation devices 201 and 202 are performing unicast communication using the MAC address learning function, the physical port used by the circuit emulation device 201 due to a communication path, a physical port, or a hardware failure to which the port belongs. Consider a case in which A1 switches from A1 to B1. Since the MAC address has a unique value for each physical port, the MAC address of the circuit emulation device 201 is changed from A1 to B1 by changing the physical port. At this time, since the MAC address B1 after the port switching is unknown to the other circuit emulation device 202, the frame transmitted from the line emulation device 201 after the port switching is received or the MAC address in the circuit emulation device 202 is received. The stored information in the learning table is reset when the aging timer expires, and the line emulation apparatus 202 continues to transmit frames to the physical port A1 before switching of the line emulation apparatus 201 until the frame is transmitted by broadcast. Cannot reach the physical port B1. Since the line emulation apparatus 201 does not always immediately transmit a frame to the line emulation apparatus 202 after switching the physical port, the line emulation apparatus 202 changes from the line emulation apparatus 202 to the line emulation apparatus 201 until the aging timer expires. On the other hand, a time during which communication is impossible occurs, and the reliability of communication is impaired.

  As a method for shortening the communication disabled time at the time of switching the physical port, a method of transmitting and receiving diagnostic signals at regular intervals between non-Ethernet network terminals can be considered. With this method, frames are always transmitted and received between circuit emulation devices, and even when a port is switched, the MAC address of the switching destination is learned in a relatively short time, and communication is impossible. Can recover from the condition. However, in this method, since a diagnostic frame is always transferred in the network, extra traffic that compresses the band for user signals is generated accordingly.

  Therefore, it is a problem to reduce the communication impossibility time at the time of switching the physical port and reduce the influence on the user communication while suppressing excessive traffic in the Ethernet network by unicast communication using the MAC address learning function. Become.

  In a circuit emulation device that performs unicast communication using the physical address (MAC address) learning function, if the physical port used for communication is switched due to a failure in the communication path, the physical port and the hardware to which the port belongs, or maintenance work, the port is changed The received device transmits a frame for urging the physical address table (MAC address (learning) table) to be updated to the changed physical address (MAC address) to the accommodated VLAN.

  The device that has received the frame (for learning update) updates the physical address table, and then unconditionally discards the frame without analyzing the payload.

  Even in a state where the circuit emulation device is performing unicast communication by the MAC address learning function, it is possible to reduce the communication disabled time when switching the physical port, and it is possible to perform communication with higher reliability.

It is a figure showing the connection of the line emulation apparatus and Ethernet network immediately after physical port switching. It is a figure showing the connection of a circuit emulation apparatus and an Ethernet network. It is a figure which shows the structural example of the network system using a circuit emulation apparatus. It is a figure showing the database of the MAC address learning table in a circuit emulation apparatus. It is a figure which shows the frame format example of the frame for MAC address learning update. It is a flowchart showing operation | movement of the circuit emulation apparatus of the side which transmits the frame for MAC address learning update. It is a flowchart showing operation | movement of the circuit emulation apparatus of the side which receives the frame for MAC address learning update. 1 is a block diagram illustrating an example of an embodiment of a circuit emulation device.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an example of a network configuration using a circuit emulation device and an Ethernet network. In FIG. 1, circuit emulation apparatuses 101, 102, 103, and 104 are ports A1, B1, A2, B2, A3, B3, A4, and B4 connected to the Ethernet network, and ports C1, C2, C3, connected to the non-Ethernet network, respectively. C4. Non-Ethernet network terminals 111, 112, 113, and 114 are connected to physical ports connected to the non-Ethernet network, and layer 2 switches 121, 122, 123, and 124 are connected to physical ports connected to the Ethernet network. The physical ports on the Ethernet network side are duplicated, one operating as the active system and the other as the standby system. The standby port is blocked and frame transmission / reception is performed only by the active system. When a failure occurs in the communication path, the operating physical port, or the hardware to which the port belongs, the communication is continued by automatically switching to the standby physical port. If the physical port needs to be switched due to maintenance work or the like, it can also be switched manually. Each of the physical ports A1, B1, A2, B2, A3, B3, A4, and B4 has an independent MAC address (physical address), and here, it is assumed that a MAC address having the same name as the physical port name is set. . Layer 2 switches 121, 122, 123, and 124 are connected in a loop to provide a redundant configuration. When a failure occurs in a communication path or a layer 2 switch, the path is switched to a path without a failure to maintain communication. . In addition, STP is used to prevent a logical loop. STP prevents logical loops by blocking specific ports. Blocked ports do not send or receive frames. Here, it is assumed that the port P22 of the layer 2 switch 122 is blocked by the STP.

  A VLAN for performing Point to Point communication is set between the circuit emulation devices. Broadcast domains are divided by setting individual VLANs for each connection device. VLAN is managed by VLANID. A port belonging to the layer 2 switch is set for each VLAN ID, and a broadcast frame flows only in this port. A VLAN ID 132 (ports: P11, P12, P13, P21, P22, P23, P31, P32, P34, P41, P42, P44) is set between the line emulation apparatuses 101 and 102. The VLAN ID 133 (affiliated ports: P11, P12, P13, P21, P22, P23, P31, P32, P33, P41, P42, P45) is set between them, and the VLAN ID 134 (affiliated port) is set between the line emulation apparatuses 101 and 104. : P11, P12, P13, P21, P22, P23, P31, P32, P35, P41, P42, P43) are set.

  Furthermore, the circuit emulation devices 101, 102, 103, and 104 have a MAC address learning function for reducing unnecessary traffic that flows through redundant paths, and transmit and receive frames by unicast. The correspondence relationship between the transmission destination MAC address of the frame received from another device and the VLAN ID is stored in the MAC address learning table in the device. The destination MAC address is specified when performing unicast communication using this database. When the MAC address is not learned, a broadcast address is assigned to the destination MAC address, and the frame is transmitted by broadcast. Also, an aging timer is set in the learning table, the non-communication time with the accommodated VLAN is counted, and when the time set in the aging timer (for example, 300 seconds) expires, the corresponding stored information is deleted. When a frame from another source MAC address is received before the aging time of the accommodated VLAN expires, the learning table is overwritten and updated with priority given to the source MAC address of the frame received later.

  In the configuration of FIG. 1 described above, the circuit emulation apparatuses 101 and 102 will be described by taking an example in which unicast communication is performed using the physical ports A1 and A2, respectively. When a failure occurs in the physical port A1 and the hardware to which the port belongs, the line emulation apparatus 101 detects an abnormality and switches the physical port used for frame transmission / reception from A1 to B1. Since the circuit emulation device 101 side stores the MAC address A2 of the physical port A2 of the circuit emulation device 102 in the learning table, it is possible to transmit a frame by unicast or broadcast immediately after switching the port. 102 cannot recognize that the MAC address of the line emulation apparatus 101 has been changed from A1 to B1 until the frame from the line emulation apparatus 101 is received. Therefore, after switching the physical port, the circuit emulation apparatus 101 generates a MAC address (physical address) learning table update frame (update frame), and for the VLAN addressed to it (VLAN ID: 132, 133, 134), Each broadcast is transmitted individually. The generation of the update frame may be performed immediately after the physical port is switched. Further, the update frame addressed to the VLAN may be transmitted to all paths in which the VLAN ID is set. This frame has a role of updating the database of the destination MAC address learning table. The number of times an update frame is issued per VLAN ID and the transmission interval may be one, or may be multiple in consideration of frame discard due to congestion in the network. The transmission of the MAC address learning table update frame is automatically issued after the physical port is switched, but manual transmission by inputting an external command is also possible.

  FIG. 5 shows the frame format of the MAC address learning table update frame of this embodiment. This frame includes a destination MAC address 501, a transmission source MAC address 502, a VLAN tag 503, a circuit emulation frame header 504, a payload 505, and an FCS (Frame Check Sequence) 506.

  The destination MAC address 501 indicates the MAC address information of the physical port of the circuit emulation device that is the frame transmission destination. When the MAC address is not learned or when a MAC address learning update frame is issued, a broadcast address is assigned to this field. When the MAC address has already been learned, an individual MAC address is designated as the destination MAC address 501 so that unicast frame transmission / reception is performed between the circuit emulation devices.

  The transmission source MAC address 502 indicates the MAC address information of the physical port of the circuit emulation device that is the transmission source of the frame. In the MAC address learning table of the circuit emulation device in this embodiment, the correspondence between the MAC address of this field and the VLAN ID is stored. In the MAC address learning table update frame, the MAC address information of the switching destination port is described in the transmission source MAC address 502. The circuit emulation device that has received the update frame updates the MAC address learning table based on the information in this field.

  A VLAN tag 503 indicates information for using the VLAN, and its description method is defined in IEEE 802.1Q. In the circuit emulation device, VLAN setting is performed for each connected device to perform point-to-point communication. The 12-bit VLAN ID in the VLAN tag 503 is stored in the MAC address learning table database in the device in pairs with the MAC address, and the MAC address learning table update frame is sent to all VLANs accommodated by the device. Issue.

  The circuit emulation frame header section 504 is a header section unique to the circuit emulation apparatus, and this field includes information for determining whether this frame is a user frame or a MAC address learning table update frame. The description method of information for discriminating two types of frames is arbitrary, and here, for example, it is assumed that discrimination is performed based on whether a specific bit is 0 or 1. A frame whose specific bit for discrimination is 0 represents a user frame, and the frame after updating the MAC address learning table is not discarded. In normal frame transmission / reception, this bit is always set to 0. When the specific bit for determination is 1, it indicates that the frame is a MAC address learning table update frame issued at the time of physical port switching. Immediately after the occurrence of physical port switching due to maintenance work or failure, a MAC address learning table update frame with this bit set to 1 is generated, and the physical port MAC address information of the switching destination is described in the source MAC address 502 and accommodated Transmission is performed individually to each VLAN. The device that has received this frame updates the MAC address learning table with the MAC address information after switching. Then, it is unconditionally discarded without analyzing the payload 504. This does not affect user communication.

  A payload 505 is a user information section. In the circuit emulation device, non-Ethernet network data is encapsulated in this field in order to transmit non-Ethernet network data using the Ethernet network. Since the MAC address learning table update frame is a frame intended only to update the learning table of another device, the frame is discarded without analyzing the payload 505. For this reason, any information contained in the payload 505 does not affect the user's communication, but for example, all 0s are assigned to this field.

  FCS 506 is a field for detecting a frame transmission error. A CRC (Cyclic Redundancy Check) value calculated from each field in the frame is set. If the value on this field does not match between the receiving side and the sending side, it is determined that an error has occurred and the frame is discarded.

  FIG. 6 is a flowchart showing the operation of the circuit emulation device on the side that transmits the MAC address learning table update frame, and FIG. 7 shows the flowchart that shows the operation of the circuit emulation device on the side that receives the MAC address learning table update frame. .

  FIG. 8 is a block diagram showing an embodiment of a circuit emulation device. With this configuration, the circuit emulation device can operate. As shown in FIG. 8, the circuit emulation device includes physical ports 801 and 802 connected to the Ethernet network. These physical ports are duplicated as described above, one operating as an active system and the other as a standby system. The standby port is blocked and frame transmission / reception is performed only by the active system. The state of the physical ports 801 and 802 is constantly monitored by the port monitoring unit 803, and when an abnormality is detected in the operational system port, information is immediately transmitted to the port switching unit 804, and switching to the standby system port is executed. In addition, manual port switching by external signal input using the switching instruction unit 814 is also possible. Hereinafter, the physical port 801 is referred to as an operational port.

  An operation when the physical port 801 on the Ethernet network side receives a frame will be described. The frame received by the physical port 801 on the Ethernet network side is transmitted to the frame receiving unit 805. The frame receiving unit 805 reads the information of the VLAN tag 503 in the frame and inquires about the VLAN ID described in this field and the VLAN ID stored in the VLAN table 806. As a result of the inquiry, a frame that is not an accommodation VLAN is discarded, and the frame of the accommodation VLAN is transmitted to the transmission source MAC address / header monitoring unit 807. The transmission source MAC address / header monitoring unit 807 also has a function of an update control unit that updates the MAC address learning table 808, and inquires the transmission source MAC address 502 of the frame with the MAC address learning table 808. If so, the learning table is updated. Further, the source MAC address / header monitoring unit 807 reads the circuit emulation device frame header unit 505 in the frame. It is determined whether the frame received in the information of this field is a user frame or a MAC address learning table update frame. If the frame is a MAC address learning table update frame, the frame is discarded after the MAC address learning table 808 is updated. In this case, the data is transmitted to the frame conversion unit 809. The frame conversion unit 809 extracts the non-Ethernet network signal from the payload 505 of the Ethernet frame and transmits it from the physical port 810 on the non-Ethernet network side.

  An operation when the physical port 810 on the non-Ethernet network side receives a signal will be described. The signal received at the physical port on the non-Ethernet network side is transmitted to the frame conversion unit 809, converted into an Ethernet frame containing the non-Ethernet network signal in the payload 505, and then transmitted to the destination MAC address assignment unit 811. The destination MAC address assigning unit 811 assigns a destination MAC address 501 corresponding to the VLAN ID from the MAC address learning table 808. If the MAC address is not learned, a broadcast address is assigned. The frame with the destination MAC address information is transmitted from the physical port 801 on the Ethernet network side via the frame transmission unit 712. The frame transmission unit 812 inserts the MAC address learning table update frame generated by the MAC address learning table update frame generation unit 813.

  Here, the operation when a failure occurs in the physical port 801 will be described. When a failure occurs in the physical port 801, the port monitoring unit 803 detects an abnormality in the physical port 801 and transmits information on the occurrence of the abnormality to the port switching unit 804. The port switching unit 804 switches the physical port used for communication from the physical port 801 to the physical port 802 based on information from the port monitoring unit 803. In response to the switching, the port switching unit 804 instructs the MAC address learning table update frame generation unit 813 to generate an update frame. The MAC address learning table update frame generation unit 813 generates an update frame for the VLAN ID held in the VLAN table 806. The frame transmission unit 812 inserts an update frame, and transmits the MAC address learning table update frame from the physical port 802 after switching. Here, when an update frame is generated for all VLAN IDs held in the VLAN table 806, communication with higher reliability can be performed.

  As described above, according to the present embodiment, it is possible to reduce the communication disabled time at the time of physical port switching due to maintenance work or failure of the circuit emulation device performing unicast communication by the MAC address learning function, and to the user communication. The influence can be reduced.

101-104, 201-204, 301, 302 ... circuit emulation devices 111-114, 211-214, 306, 307 ... non-Ethernet network terminals 121-124, 221-224 ... layer 2 switch 141, 241, 308 ... Transmission path 303 ... Ethernet network 304, 305 ... Non-Ethernet network transmission device 501 ... Destination MAC address 502 ... Source MAC address 503 ... VLAN tag 504 ... Circuit emulation frame header 505 ... Payload 506 ... FCS
801, 802, A1 to A4, B1 to B4 ... Physical ports of the circuit emulation device (Ethernet network connection side)
803: Port monitoring unit 804: Port switching unit 805 ... Frame receiving unit 806 ... VLAN table 807 ... Source MAC address / header monitoring unit 808 ... MAC address learning table 809 ... Frame conversion unit 810, C1 to C4: Physical port of circuit emulation device (non-Ethernet network connection side)
811 ... Destination MAC address assigning unit 812 ... Frame transmitting unit 813 ... MAC address learning table update frame generating unit 814 ... Switching instruction units P11-13, P21-23, P31-35, P41- 45 ... physical port of layer 2 switch

Claims (9)

A first physical port having a first physical address;
A second physical port having a second physical address;
A port switching unit that switches between the first physical port and the second physical port;
A frame generation unit that generates a frame including physical address information and identification information of a switching destination in response to switching by the port switching unit;
A circuit emulation device having a frame transmission unit for transmitting the frame.   2. The circuit emulation according to claim 1, wherein the frame generation unit generates the frame by including the physical address information of the switching destination in a transmission source physical address and including identification information in a frame header unit. apparatus.   A physical address table that stores physical addresses of other devices; and an update control unit that updates the physical address table according to the identification information when receiving the frame generated by another circuit emulation device. The circuit emulation device according to claim 1.   2. The circuit emulation according to claim 1, wherein the frame transmission unit transmits the frame to an accommodated VLAN in accordance with switching between the first physical port and the second physical port. apparatus.   4. The circuit emulation device according to claim 3, wherein the update control unit determines whether or not the frame is a frame for updating a physical address table according to the identification information.   2. The circuit emulation device according to claim 1, wherein a VLAN ID is set for the VLAN, and the frame is transmitted by broadcast from the frame transmission unit. The circuit emulation device according to claim 1, wherein the frame is discarded after the physical table is updated.   The circuit emulation device according to claim 1, wherein the frame is discarded without analyzing the payload according to the update of the physical table.   2. The circuit emulation according to claim 1, wherein the frame generation unit generates the frame in response to automatic switching between the first physical port and the second physical port or an instruction from the outside. apparatus.

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