JP2006270680A - Layer two switch device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a layer two switch device for rewriting the destination address into the MAC address of a predetermined broad band access server for transmission upon receiving a PADI packet. <P>SOLUTION: The two layer switch device 3 equipped with at least two connection ports 35 for transmitting a layer two level packet received by any of the connection ports 35 from at least one of the residual connection parts 35 is provided with a packet processing part 31 for controlling the transmission/reception of a packet, an address database 33 for storing the MAC address of a communicatively connected broad band access server (BAS4) and distribution policy information 34 in which the selection policy of the BAS4 is stored. Then, when the packet is a PADI packet, the packet processing part 31 selects one BAS4 from the address database 33 based on the distribution policy information 34, and rewrites the destination address of the packet into the MAC address of the selected BAS4 for transmission. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a layer 2 switch apparatus that transmits and receives layer 2 level packets.

  In general, an access method in a broadband network is PPPoE (abbreviation of “PPP over Ethernet”) that can use a PPP (point-to-point protocol) authentication function on Ethernet (registered trademark), and is defined in RFC2516. ) Is used.

  FIG. 6 shows a network configuration using PPPoE. Usually, PPPoE software 1a is installed in a terminal (computer) 1 of a subscriber of a broadband network, and this terminal 1 is connected to a communication company's concentrator (layer 2 switch device 3) via a DSL modem 2. It is connected. This layer 2 switch device 3 is connected to a broadband access server (BAS) 4 which is a system for managing subscribers, and further connected to a system 5 of the Internet service provider (ISP) and the Internet 6 via this BAS 4. Yes.

  The BAS 4 communicates with the subscriber terminal 1 using PPPoE, authenticates the subscriber, and simultaneously connects to the ISP system 5 designated by the subscriber. Therefore, if a failure occurs in BAS4 or if it is stopped for maintenance, the subscriber will not be able to use the network. Therefore, the telecommunications carrier broadcasts so that the continued service can be provided to the subscriber. Multiple BAS4 units are installed in the domain to ensure reliability. The process in which the terminal 1 selects one from the plurality of BASs 4 is also performed using PPPoE (see, for example, Patent Document 1).

JP 2003-198580 A

  However, when selecting BAS4 using PPPoE, which BAS4 is selected depends on the processing of the terminal 1 (PPPoE software 1a), and the communication carrier cannot control it. Therefore, there is a problem that sessions cannot be equally distributed to a plurality of BASs 4 for load balancing, or a problem that sessions cannot be concentrated on a predetermined BAS 4 (a BAS 4 that is not subject to maintenance) in preparation for maintenance or the like. there were.

  There is a method of explicitly specifying the BAS 4 to be connected in the PPPoE software 1a installed in the terminal 1, but the software 1a capable of such setting is a special one, and the address (MAC address) of the BAS 4 is set. Even if it can be specified, a means for notifying the subscriber, setting by manual input, and the like are required, which is not realistic.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a layer 2 switch device that, when receiving a PADI packet, rewrites the destination address to the MAC address of a predetermined broadband access server and transmits it. And

  In order to solve the above-described problem, a layer 2 switch device according to the present invention has at least two or more connection ports, and any of the connection ports receives a layer 2 level packet received from at least the remaining connection ports. Packet processing means (for example, the packet processing unit 31 in the embodiment) that controls transmission / reception of packets, an address database that stores MAC addresses of broadband access servers capable of communication, and broadband access And distribution policy information in which a server selection policy is stored. Then, when the received packet is a PADI packet, the packet processing means selects one broadband access server from the address database based on the distribution policy information, and sets the destination address of the packet to the selected broadband access server. It is configured to rewrite to a MAC address for transmission.

  At this time, it is preferable that the packet processing means is configured to determine that the received packet is a PADI packet when the ether type of the packet is 0x8863 and the destination address is a broadcast address.

  In addition, it has BAS monitoring means for monitoring the broadband access server (for example, the BAS monitoring unit 32 in the embodiment), and this BAS monitoring means sets the MAC address of the broadband access server stored in the address database as the destination address. The PAD packet is transmitted, and the state of the broadband access server to which the PADO packet is returned in response to this PADI packet is stored in the address database as normal, and the packet processing means selects the broadband access server that is in the normal state. The packet is preferably configured to rewrite the destination address of the packet. Alternatively, the BAS monitoring means transmits a PADI packet with a broadcast address set as the destination address, stores the state of the broadband access server to which the PADO packet is returned in response to this PADI packet as normal, and stores it in the address database. Preferably, the means is configured to select a broadband access server in a normal state and rewrite the destination address of the packet.

  Further, the packet processing means is configured to store the number of terminals assigned to the broadband access server, and the distribution policy information selects the broadband access server having the smallest number of terminals and rewrites the packet destination address. It is preferable that it is set to.

  Alternatively, the packet processing means is configured to store a broadband access server that is not subject to rewriting of the destination address, and the distribution policy information selects a broadband access server excluding the broadband access server that is not subject to rewriting. The destination address of the packet is preferably set to be rewritten.

  When the layer 2 switching device according to the present invention is configured as described above, the destination address of the PADI packet can be rewritten by this layer 2 switching device without affecting the terminal or the broadband access server to be connected by PPPoE. Thus, the selected broadband access server can be controlled, and a plurality of broadband access servers can be provided to the subscriber to ensure reliability while enabling flexible operation when the system is healthy. At this time, the PADI packet can be identified from the packets transmitted and received by the layer 2 switching device 3 by examining the ether type and the destination address of the packet.

  In addition, by sending a PADI packet from this layer 2 switch device and monitoring the status of the broadband access server to which the PADO packet is returned as normal, the broadband access server in which a failure has occurred or stopped is designated as the destination address. Can be excluded from the target of rewriting, and reliability can be improved.

  Furthermore, load distribution can be performed by storing the number of terminals assigned by rewriting the destination address for each broadband access server and allocating the broadband access server having the smallest number of assigned terminals. Alternatively, by storing and not allocating a broadband access server that is not subject to rewriting of the destination address, it is possible to prevent the broadband access server planned for maintenance or the like from being rewritten as the destination address.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, a process in which the terminal 1 selects one of a plurality of BASs 4 and starts communication using PPPoE will be described with reference to FIG. In PPPoE, there are a stage for establishing a session by searching for BAS 4 (discovery stage) and a stage for communicating with the Internet 6 and the like through the established session (PPP session stage), but here only for the discovery stage explain.

  When the terminal 1 is connected to the network, first, a PADI (PPPoE Active Discovery Initiation) packet is transmitted. In this PADI packet, an Ethernet broadcast address is set as a destination address of the Ethernet frame. Therefore, the layer 2 switch device 3 that has received the PADI packet duplicates and transmits the PADI packet from the ports of the layer 2 switch device 3 other than the port to which the terminal 1 is connected.

  The BAS 4 (first BAS 4a and second BAS 4b) that has received the PADI packet transmits a PADO (PPPoE Active Discovery Offer) packet to the terminal 1, respectively. At this time, the MAC address of the terminal 1 that has transmitted the PADI packet is set as the destination address of the PADO packet (that is, a unicast address is set). The terminal 1 receiving this PADO packet selects one BAS 4 from these PADO packets, and transmits a PADR (PPPoE Active Discovery Request) packet to the BAS 4. FIG. 1 shows a case where the first BAS 4a is selected. The destination address of this PADR packet is also a unicast address, and the MAC address of the first BAS 4a is set. Finally, the first BAS 4a that has received this PAD packet transmits a PADS (PPPoE Active Discovery Session-confirmation) packet to the terminal 1, ends the discovery stage, and the terminal 1 that has received this PADS packet enters the PPP session stage. Transition. The destination address of this PADS packet is also unicast, and the MAC address of the terminal 1 is set.

  Although not shown, when the PPPoE session is terminated, a PADT (PPPoE Active Discovery Terminate) packet is transmitted. The destination address of this packet is also a unicast address.

  Now, a description will be given of the layer 2 switch device 3 for the communication carrier to control the BAS 4 to be connected regardless of the terminal 1 in the discovery stage in PPPoE. When receiving a PADI packet (broadcast packet) from the terminal 1, the layer 2 switching device 3 transmits the packet only to a predetermined BAS 4. As shown in FIG. 2, the layer 2 switching device 3 has a plurality of ports 35 (35a to 35c), and is connected to the terminals 1 and BAS 4 (4a, 4b) connected to these ports 35. A packet processing unit 31 that forwards and receives packets transmitted and received by the BAS 4 and a BAS monitoring unit 32 that monitors the BAS 4 and controls the BAS 4 assigned to the PADI packet received from the terminal 1 by the packet processing unit 31.

  When the destination address of the packet transmitted from the terminal 1 is a unicast address, the packet processing unit 31 transmits the packet from the port 35 (35b or 35c) corresponding to the unicast address. The packet is duplicated and transmitted from a predetermined port (in this case, ports 35b and 35c to which BAS4 is connected). Further, when the layer 2 switch device 3 receives the PADI packet from the terminal 1 and the address database 33 in which the MAC address of the BAS 4 communicable with the layer 2 switch device 3 (within the same broadcast domain) is stored. And distribution policy information 34 for determining which BAS 4 the PADI packet is transmitted to.

  Here, the address database 33 may be configured such that the communication carrier sets in advance the MAC address of the BAS 4 that can communicate with the layer 2 switch device 3, and the BAS monitoring unit 32 may be configured by the packet processing unit 31. By sending a PADI packet (broadcast packet) to the BAS 4 via the BAS 4, receiving the PADO packet transmitted from the BAS 4 that received it, and scanning the connected BAS 4, the BAS 4 set in this PADO packet The MAC address may be stored in the address database 33.

  Further, since the terminal 1 cannot communicate if a failure occurs in the BAS 4 or is stopped due to maintenance, the BAS monitoring unit 32 is configured to monitor the state of the BAS 4 at predetermined time intervals. Yes. For example, as shown in FIG. 3, the BAS monitoring unit 32 uses the MAC address of each BAS 4 as a destination address (ie, as a unicast packet) for each BAS 4 stored in the address database 33 at regular intervals. BAS4 that has transmitted a PADI packet and has returned a PADO packet within a predetermined time is stored in the address database 33 as being in a normal state, and if the PADO packet cannot be received within a predetermined time, It is stored in the address database 33 as being in an abnormal state. At this time, it is also possible to configure the BAS 4 that transmits the PADI packet as a broadcast packet and returns the PADO packet within a predetermined time and stores it in the address database 33 as being in a normal state.

  As described above, the packet processing unit 31 of the layer 2 switching device 3 identifies the packet transmitted from the terminal 1 and received by the port 35a in the discovery stage as shown in FIG. 4, and when the packet is a PADI packet Is configured so that the destination address of the Ethernet frame is selected and replaced from the address database 33 based on the distribution policy information 34 and transmitted from the predetermined ports 35b and 35c (in FIG. 4, the first BAS 4a is selected). Shows the case). This process will be described with reference to FIG.

  When the packet processing unit 31 receives a packet from the port 35 (for example, the port 35a), the packet processing unit 31 checks whether the ether type constituting the Ethernet frame of the packet is 0x8863 (step S100). As described above, in PPPoE, there are a discovery stage and a PPP session stage. In the discovery stage, 0x8863 is set in the ether type, and in the PPP session stage, 0x8864 is set in the ether type. When the ether type is not 0x8863, since it is not a PADI packet, the packet is transmitted as it is from the port 35 (35b, 35c) (step S103).

  If the ether type of the received packet is 0x8863 (step S100), it is next checked whether the destination address constituting the Ethernet frame is a broadcast address (step S101). Among the packets (PADI, PADO, PADR, PADS, PADT) transmitted when the Ether type is 0x8863, that is, the discovery stage in PPPoE, the broadcast address is set as the destination address when the PADI packet is set. Because it is only. If the destination address is not a broadcast address, the packet is transmitted as it is from the port 35 (35b, 35c) (step S103).

  If the destination address of the received packet is a broadcast address (step S101), the packet processing unit 31 starts from one in the normal state among the BASs 4 stored in the address database 33 according to the distribution policy information 34. The base BAS 4 is selected, and the destination address of the received packet is rewritten to the MAC address (that is, the unicast address) (step S102).

  The packet processing unit 31 is configured to monitor the PADS packet and store the number of terminals connected to each BAS 4. Specifically, when receiving the PADS packet, the packet processing unit 31 is configured to count and store the number of terminals connected to the BAS4 (corresponding number of PPPoE session IDs) for each BAS4 MAC address. Has been. The packet processing unit 31 monitors the PADT packet and is configured to reduce the number of terminals connected to the BAS 4 when the PPPoE session ends. Similarly, it is configured to reduce the number of terminals connected to a PPPoE session that has not been communicated for a certain period of time.

  Here, the setting content of the distribution policy information 34 is set to a distribution policy of “select the BAS 4 with the smallest number of connected terminals from the number of terminals for each BAS 4 stored in the packet processing unit 31”. be able to. As a result, the terminals 1 can be distributed to the plurality of BASs 4 so that the loads are equalized. Alternatively, when there is a BAS 4 that performs maintenance, information on the BAS 4 is stored in the packet processing unit 31 as an exclusion target BAS, and the packet processing unit 31 “excludes the exclusion target BAS from the selection target”. Can be set to the distribution policy. As a result, after the setting, the terminal 1 connected to the excluded BAS 4 (the destination address is rewritten) disappears, and even if the BAS 4 is stopped for maintenance, the subscriber is not affected by the maintenance. Can do.

  The packet whose destination address has been rewritten as described above is transmitted from the port 35 (35b, 35c) (step S103). In this address replacement process (S102), rewriting is not performed except for the destination address (for example, the transmission source address).

  When the layer 2 switch device 3 is configured as described above, the layer 1 switch device 3 controls the selection of the BAS 4 to be used while the terminal 1 (PPPoE software 1a) and the BAS 4 are in use. Therefore, it is possible to distribute the load by equally distributing the number of terminals 1 connected to the BAS 4 and to prevent the terminals 1 from being connected to the BAS 4 that is stopped due to maintenance or the like. A plurality of BASs 4 can be provided to ensure reliability while enabling flexible operation when the system is healthy.

It is a diagram which shows the exchange of the packet between a terminal and BAS in a discovery stage. It is a block diagram which shows the structure of the layer 2 switch apparatus which concerns on this invention. It is a diagram which shows the exchange of a packet when BAS is monitored. It is a diagram which shows when a PADI packet is rewritten. It is a flowchart which shows the rewriting process of a destination address. It is a block diagram which shows the structure of the network using PPPoE.

Explanation of symbols

3 Layer 2 switch device 4 BAS (Broadband Access Server)
31 Packet processing unit (packet processing means)
32 BAS monitoring unit (BAS monitoring means)
33 Address database 34 Distribution policy information 35 Port

Claims (6)

A layer 2 switching device having at least two or more connection ports and transmitting a layer 2 level packet received by any of the connection ports from at least one of the remaining connection ports;
Packet processing means for controlling transmission and reception of the packet;
An address database in which MAC addresses of communicable broadband access servers are stored;
Distribution policy information in which a selection policy of the broadband access server is stored;
The packet processing means is
When the received packet is a PADI packet,
A single broadband access server is selected from the address database based on the distribution policy information, and the destination address of the packet is rewritten to the MAC address of the selected broadband access server and transmitted. A layer 2 switching device. The packet processing means is
The configuration of claim 1, wherein the received packet is a PADI packet when the ether type of the packet is 0x8863 and the destination address is a broadcast address. Layer 2 switch device. BAS monitoring means for monitoring the broadband access server,
The BAS monitoring means transmits a PADI packet in which the MAC address of the broadband access server stored in the address database is set as the destination address, and the broadband access in which a PADO packet is returned to the PADI packet Store the server status as normal in the address database,
3. The layer 2 switch according to claim 1, wherein the packet processing unit is configured to select the broadband access server in which the state is normal and rewrite the destination address of the packet. 4. apparatus. BAS monitoring means for monitoring the broadband access server,
The BAS monitoring means transmits a PADI packet in which a broadcast address is set as the destination address, stores the state of the broadband access server to which the PADO packet is returned in response to the PADI packet as normal, and stores it in the address database.
3. The layer 2 switch according to claim 1, wherein the packet processing unit is configured to select the broadband access server in which the state is normal and rewrite the destination address of the packet. 4. apparatus. The packet processing means is configured to store the number of terminals allocated to the broadband access server;
5. The distribution policy information according to claim 1, wherein the distribution policy information is set to select the broadband access server having the smallest number of terminals and rewrite the destination address of the packet. Layer 2 switch device. The packet processing means is configured to store the broadband access server that is not subject to rewriting of the destination address;
2. The distribution policy information is set so as to rewrite the destination address of the packet by selecting the broadband access server by excluding the broadband access server not to be rewritten. The layer 2 switch apparatus in any one of -4.

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