JP2007110654A - Bridge device and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bridge device capable of dealing with a problem of MTU unmatching in applying multicast or flooding processing to a frame, and a control method of the bridge device. <P>SOLUTION: The bridge device receives mutlicast frames from a transmission source terminal by a receiver side network interface, and transmits it to a plurality of transmitter side network interfaces. The bridge device is provided with a means for acquiring a value of a first maximum transfer unit owned by the receiver side network interface, and receiving values of a plurality of second maximum transfer units owned by the plurality of the transmitter side network interfaces; and a means for transmitting an ICMP (internet control message protocol) packet including the minimum value of the maximum transfer unit, if the minimum value of the value of the plurality of second maximum transfer units is smaller than the value of the first maximum transfer unit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bridge device applied to an IP network and a bridge device control method.

  In the Internet Protocol, which performs end-to-end communication by sending and receiving packets, the packet size that can be handled by the terminals at both ends of communication is basically free (but maximum The size is 65535). However, since IP packets are exchanged on a data link layer such as Ethernet (registered trademark) or PPP (Point-to-Point Protocol), the size of the packet is inevitably set to a size that can be transmitted by the data link layer. It can be said that keeping the maximum number is the most efficient transfer. The size of this packet is called MTU (Maximum Transfer Unit).

  Usually, in the case of Ethernet, the value of the MTU is 1500, and when performing IP communication, communication is performed by the MTU 1500. For example, in the case of a LAN connected by Ethernet, it is the most efficient state that any terminal communicates with the MTU 1500. Since the value of 1500 is not normally changed, devices such as a bridge and a switching hub used for extending the Ethernet do not particularly process the MTU. Although IP packets with a size exceeding the MTU are fragmented at the IP layer, devices such as bridges and hubs are not devices that process IP, so packets larger than those that can be processed by these devices are discarded. Become.

  With the enhancement of the network environment in homes, SOHO (Small Office Home Office) and general offices, and the spread of infrastructure for broadband networks and public wireless Internet connection, these homes, SOHOs and offices can be safely accessed via the Internet. There is an increasing demand for connection. Normally, it may be assumed that the MTUs are uniform, but the MTU may change when tunneling is performed in order to perform communication using the same IP segment as that of the remote network. “Tunneling” is a general term for technologies for generally wrapping IP packets (or Ethernet frames, etc.) in another IP packet and transferring them. L3VPN (Layer 3 Virtual Private Network), L2VPN (Layer 2 Virtual Private Network) Such a technique is known. For L2VPN, more specific techniques include L2TP (Layer 2 Tunneling Protocol) and MPLS (Multi Protocol Label Switching).

  For example, when encapsulating layer 2 (L2) with layer 3 (L3) and emulating layer 2 thereby, the maximum payload is reduced by the header for encapsulation in the packet format. MTU will be reduced. When bridging layer 2 emulated in this way based on IEEE 802.1D, the bridge device must be aware that the MTU is different. For example, consider an L2 bridge between MTU 1500 and MTU 1454. Frames of MTU 1455 and higher are discarded without being forwarded by the L2 bridge. At this time, layer 3 is not notified that the frame has been discarded.

  This problem needs to be considered even when the bridge device transfers a multicast frame or when a unicast frame is flooded.

  Accordingly, an object of the present invention is to provide a bridge device and a control method for the bridge device that can cope with the problem of MTU mismatch when multicasting or flooding a frame.

  A bridge device according to an aspect of the present invention is a bridge device that receives a multicast frame from a transmission source terminal via a reception-side network interface and transmits the multicast frame to a plurality of transmission-side network interfaces. Means for obtaining a value of a transfer unit and obtaining values of a plurality of second maximum transfer units possessed by the plurality of transmission side network interfaces; and a minimum value among the values of the plurality of second maximum transfer units. And a means for transmitting an ICMP packet including the minimum value of the maximum transfer unit to the transmission source terminal if the value is smaller than the value of one maximum transfer unit.

  According to the present invention, an object of the present invention is to provide a bridge device and a control method for the bridge device that can cope with the problem of MTU mismatch when multicasting or flooding a frame.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a network to which a bridge device according to an embodiment of the present invention is applied. As shown in the figure, terminal B to terminal E are connected to terminal A via bridge device 1. The bridge device 1 transfers the frame transmitted from the terminal A to any one of the terminals B to E, or conversely, the frame transmitted from any one of the terminals B to E to the terminal A. Transfer process. In order to realize such a basic function as a bridge, the bridge device 1 includes a MAC address learning unit 2 and an L2 bridge frame transfer processing unit 3. The MAC address learning unit 2 performs MAC address learning based on, for example, IEEE 802.1D specifications. The L2 bridge frame transfer processing unit 3 performs a bridge forwarding process based on the IEEE 802.1D specification.

  In the first to fourth embodiments of the present invention, the bridge device 1 receives, for example, a multicast frame from a transmission source terminal corresponding to the terminal A in FIG. The present invention relates to a bridge device that takes measures against a problem of MTU mismatch when performing so-called multicast transmission to a port of a side network interface.

  In the fifth to seventh embodiments of the present invention, when the bridge device 1 receives a unicast frame from a transmission source terminal corresponding to, for example, the terminal A in FIG. The present invention relates to a bridge device that takes measures against a problem of MTU mismatch when performing so-called flooding processing, in which a unicast frame is transmitted to all transmission side network interfaces if the frame transfer destination is unsolved.

(First embodiment)
FIG. 2 is a block diagram showing a function expansion portion in the bridge device shown in FIG. 1 according to the first embodiment of the present invention. As shown in the figure, in addition to the components shown in FIG. 1, the bridge device 1 according to the present embodiment includes an MTU determination unit 40, an ICMP processing unit 50, an MTU holding unit 6, an IP transmission source / destination. And holding unit 7.

  The MTU determination unit 40 reads the MTU (maximum transfer unit) value of the port that has received the multicast frame from the MTU holding unit 6 and stores it, for example, a storage unit 41 such as a register, and all ports other than this reception port. Each of the MTU values is read from the MTU holding unit 6 and stored. For example, a storage unit 42 such as a register, a comparator (COMP) 43 that compares the values of the storage unit 41 and the storage unit 42, and a comparator 43 And a determination unit 44 that determines how to process the multicast frame according to the comparison result. Specific processing contents of the determination unit 44 will be described later.

  When the MAC address learning unit 2 learns the MAC address based on the IEEE 802.1D specification, the MTU determination unit 40 simultaneously determines the MTU value for each network interface corresponding to the device connected to the network. Acquired and stored in the MTU holding unit 6. The present invention is not limited to a specific method as to how to acquire the MTU value. For example, the MTU determination unit 40 determines the MTU value from the MTU value acquisition unit 51 in the ICMP processing unit 50. The acquisition of is instructed. In response to this, the MTU value acquisition unit 51 acquires the MTU value of each device in the network by, for example, a path MTU discovery function based on ICMP.

  The L2 bridge frame transfer processing unit 3 performs bridge forwarding processing based on the IEEE 802.1D specification as described above. Whether or not this forwarding processing should be executed depends on the processing result of the determination unit 44. Controlled.

  The ICMP processing unit 50 includes an MTU value acquisition unit 51 and an ICMP packet transmission unit 52.

  The MTU value acquisition unit 51 has the above-described path MTU detection function. The ICMP path MTU detection is defined in RFC 1191 in IPv4 and in RFC 1981 in IPv6. As a general procedure for path MTU detection, a DF flag (fragment prohibition flag) is set in an IP packet, and the IP packet is transmitted with various changes in the MTU size. In response, an ICMP destination unreachable message is received and an MTU value set in the message is obtained.

  The ICMP packet transmission unit 52 transmits an ICMP packet to the multicast frame transmission source terminal under the control of the determination unit 44 of the MTU determination unit 40.

  The IP transmission source / destination holding unit 7 stores the transmission source IP address (layer 3 address) and the destination IP address in association with the frame transfer performed in the past by the bridge device 1 in association with each other. The ICMP packet transmission unit 52 obtains the IP address from the IP transmission source / destination holding unit 7 when transmitting the ICMP packet to the transmission source terminal of the multicast frame.

  The bridge apparatus 1 of the present embodiment configured as described above addresses the problem of MTU mismatch when receiving and forwarding a multicast frame. Here, dynamic change of the MTU will be described. . Consider a case where layer 2 (L2) is encapsulated by layer 3 (L3) in the network of FIG. FIG. 3 shows a packet format when emulating L2. When emulating L2, the maximum payload P is reduced by the header amount H for encapsulation, and the MTU of layer 2 is reduced. When bridging the layer 2 emulated in this way based on IEEE 802.1D, the bridge device 1 must be aware that the MTU is different.

  For example, consider an L2 bridge between MTU 1500 (multicast frame reception port) and MTU 1454, MTU 1280, and MTU 1120 (transmission side ports). Frames of MTU 1455 and higher are discarded without being forwarded by the L2 bridge. At this time, even if it is possible to notify the transmission source terminal that a frame of MTU 1455 or higher has been discarded, if the transmission source terminal retransmits the frame of MTU 1454, it cannot still forward to each port of MTU 1280 and MTU 1120. It is a problem. This is an inherent problem when forwarding multicast frames.

  Therefore, in the bridge device 1 according to the present embodiment, when a multicast frame is received, the MTU value of the reception port is acquired and stored in the storage unit 41, and the MTU values of all transmission ports are acquired. The values are stored in the storage unit 42, and both of the values stored in the storage units 41 and 42 are compared by the comparator 43. The determination unit 44 determines whether or not the minimum value of the MTU of the transmission side port is smaller than the value of the MTU of the reception side port. If so, the ICMP packet including the minimum value of the MTU is transmitted to the transmission source. The ICMP packet transmission unit 52 is instructed to transmit to the terminal.

  FIG. 4 is a flowchart showing a procedure for processing a multicast frame by the bridge device according to the first embodiment of the present invention.

  First, the Ethernet multicast frame transmitted from the transmission source terminal is received by the bridge device 1 (step S101). At this time, the MAC address learning unit 2 performs MAC address learning based on, for example, IEEE 802.1D specifications.

  Next, the MTU value acquisition unit 51 acquires the MTU value of the port that has received the multicast frame and the MTU values of all ports other than the reception port (step S102). These MTU values are stored in the MTU holding unit 6. Note that acquisition of the MTU value is not necessarily performed after reception of the multicast frame, and the execution order of steps S101 and S102 may be switched.

  Next, the MTU value of the receiving port of the multicast frame is read from the MTU holding unit 6 and stored in the storage unit 41, and the MTU values of all other ports are similarly read from the MTU holding unit 6. It is stored in the storage unit 42. Here, the determination unit 44 determines whether there is a port having an MTU smaller than the port that has received the multicast frame (step S103). The comparator 43 compares the magnitudes of the MTU values stored in the storage units 41 and 42. If there is no port having an MTU smaller than the multicast frame reception port, the determination unit 44 transfers the L2 bridge frame so that the multicast frame is forwarded to all ports except the multicast frame reception port. An instruction is given to the processing unit 3.

  On the other hand, if it is determined in step S103 that there is a port having an MTU smaller than the multicast frame reception port, the ICMP packet transmission unit 52 sets the IP address of the multicast frame transmission source to the IP transmission source Obtained from the destination holding unit 7, the protocol type of the multicast frame is determined (step S105).

  For example, if the transmission source of the multicast frame uses IPv6 and is transmitting an IPv6 multicast frame, the ICMP packet transmission unit 52 transmits an ICMPv6 packet to this transmission source (step S106). Alternatively, when this transmission source uses IPv4, an ICMPv4 packet is transmitted to this transmission source (step S107). Note that it is preferable that these ICMP packets corresponding to the protocol type include the minimum value of the MTU of the transmission side port.

  After the ICMP packet is transmitted in step S106 or S107, the multicast frame is discarded and the current reception process is terminated (step S108).

  The transmission source that has received the notification by the ICMP packet can determine retransmission or the like by layer 3 processing of the ICMP packet. At the time of retransmission, it is possible to match the MTU for transmitting a multicast frame with the notified minimum value. Therefore, it is possible to appropriately cope with the MTU mismatch problem at the time of the multicast frame transfer processing by the bridge device 1.

(Second embodiment)
FIG. 5 is a block diagram showing a function expansion portion in the bridge device shown in FIG. 1 according to the second embodiment of the present invention. As shown in the figure, the bridge device 1 according to the present embodiment includes a multicast information learning unit 8, a multicast information holding unit 9, an MTU determination unit 40, and an ICMP processing unit in addition to the components shown in FIG. 50, an MTU holding unit 6, and an IP transmission source / destination holding unit 7.

  The multicast information learning unit 8 learns multicast information based on the IGMP / MLD snoop function (reference URL <http://www.ietf.org/internet-drafts/draft-ietf-magma-snoop-10.txt>). To be held in the multicast information holding unit 9. According to the multicast information, it is possible to specify a port to which a multicast frame should be transferred toward terminals participating in the multicast group.

  In FIG. 5, in the bridge device 1 of the present embodiment, the same reference numerals as those in the first embodiment are assigned to components that are substantially the same as those in the first embodiment. Omitted.

  The MTU determination unit 40 reads out and stores the MTU (maximum transfer unit) value of the port that has received the multicast frame from the MTU holding unit 6, for example, a storage unit 41 such as a register, and a learning result by the multicast information learning unit 8. The MTU value of the transmission target port of the specified multicast frame is read from the MTU holding unit 6 and stored, for example, a storage unit 45 such as a register, and a comparator that compares the values of the storage unit 41 and the storage unit 45 (COMP) 43 and a determination unit 44 that determines how to process the multicast frame according to the comparison result by the comparator 43. Specific processing contents of the determination unit 44 will be described later.

  The bridge device 1 according to the present embodiment addresses the problem of MTU mismatch when receiving and forwarding a multicast frame as in the first embodiment, but transmits the multicast address of the multicast frame and the multicast frame. The multicast information learning unit 8 learns multicast information that associates with a port to be used, and the MTU is determined for a limited port based on the multicast information.

  In the bridge device 1 of the present embodiment, when a multicast frame is received, the value of the MTU that the receiving port has is acquired and stored in the storage unit 41, and the multicast frame specified by the learning result by the multicast information learning unit 8 The MTU values of the transmission target ports are respectively acquired and stored in the storage unit 45, and both values stored in the storage units 41 and 45 are compared by the comparator 43. The determination unit 44 determines whether or not the minimum value of the MTU of the transmission side port is smaller than the value of the MTU of the reception side port. If so, the ICMP packet including the minimum value of the MTU is transmitted to the transmission source. The ICMP packet transmission unit 52 is instructed to transmit to the terminal.

  FIG. 6 is a flowchart showing a procedure for processing a multicast frame by the bridge device according to the second embodiment of the present invention.

  First, the Ethernet multicast frame transmitted from the transmission source terminal is received by the bridge device 1 (step S201). At this time, the MAC address learning unit 2 performs MAC address learning based on, for example, IEEE 802.1D specifications.

  Next, the multicast information learning unit 8 narrows down the transmission target (forwarding destination) ports of the multicast frame by the IGMP / MLD snoop function (step S202).

  Next, the MTU value acquisition unit 51 acquires the MTU value of the port that received the multicast frame and the MTU value of the transfer destination port (step S203). These MTU values are stored in the MTU holding unit 6. Note that the acquisition of the MTU value is not necessarily performed after the reception of the multicast frame, and the execution order of steps S201 and S203 may be switched.

  Next, the MTU value of the receiving port of the multicast frame is read from the MTU holding unit 6 and stored in the storage unit 41, and the MTU value of the transfer destination port is similarly read from the MTU holding unit 6 and stored in the storage unit. 45. Here, the determination unit 44 determines whether there is a port having an MTU smaller than the port that has received the multicast frame (step S204). The comparator 43 compares the magnitudes of the MTU values stored in the storage units 41 and 45. Then, if there is no port having an MTU smaller than the receiving port of the multicast frame, the determination unit 44 transfers the L2 bridge frame so as to forward the multicast frame to all the specified transfer destination ports. An instruction is given to the processing unit 3.

  On the other hand, if it is determined in step S204 that there is a port having an MTU smaller than the multicast frame reception port, the ICMP packet transmission unit 52 sets the IP address of the multicast frame transmission source to the IP transmission source Obtained from the destination holding unit 7, the protocol type of the multicast frame is determined (step S206).

  For example, if the transmission source of the multicast frame uses IPv6 and is transmitting an IPv6 multicast frame, the ICMP packet transmission unit 52 transmits an ICMPv6 packet to this transmission source (step S207). Alternatively, when this transmission source uses IPv4, an ICMPv4 packet is transmitted to this transmission source (step S208). Note that it is preferable that these ICMP packets according to the protocol type include the minimum value of the MTU of the transfer destination port.

  After transmitting the ICMP packet in step S207 or S208, the multicast frame is discarded and the current reception process is terminated (step S209).

  The transmission source that has received the notification by the ICMP packet can determine retransmission or the like by layer 3 processing of the ICMP packet, as in the first embodiment. At the time of retransmission, it is possible to match the MTU for transmitting a multicast frame with the notified minimum value. Therefore, it is possible to appropriately cope with the MTU mismatch problem at the time of the multicast frame transfer processing by the bridge device 1.

(Third embodiment)
FIG. 7 is a block diagram showing a function expansion portion in the bridge device shown in FIG. 1 according to the third embodiment of the present invention. As shown in the figure, the bridge device 1 according to the present embodiment includes an MTU determination unit 40, an MTU value acquisition unit 51, an MTU holding unit 6, and a fragment processing unit 100 in addition to the components shown in FIG. With.

  The fragment processing unit 100 follows the procedure of the IP protocol version and PW fragmentation (reference URL <http://www.ietf.org/internet-drafts/draft-ietf-pwe3-fragmentation-05.txt>). In addition, an IP fragment processing unit 101 and a PW fragment processing unit 102 are provided for performing appropriate fragment processing.

  In FIG. 7, in the bridge device 1 of the present embodiment, substantially the same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be given. Omitted.

  The MTU determination unit 40 reads the MTU (maximum transfer unit) value of the port that has received the multicast frame from the MTU holding unit 6 and stores it, for example, a storage unit 41 such as a register, and all ports other than this reception port. Each of the MTU values is read from the MTU holding unit 6 and stored. For example, a storage unit 42 such as a register, a comparator (COMP) 43 that compares the values of the storage unit 41 and the storage unit 42, and a comparator 43 And a determination unit 44 that determines how to process the multicast frame according to the comparison result. Specific processing contents of the determination unit 44 will be described later.

  The bridge device 1 of the present embodiment addresses the problem of MTU mismatch when receiving and forwarding multicast frames as in the first embodiment. A multicast frame is transmitted as it is to a transmission side port having the same or higher MTU value, and the multicast frame is fragmented and transmitted to a transmission side port whose MTU value is smaller than that of the reception side port. This is different from the first embodiment.

  In the bridge device 1 of the present embodiment, when a multicast frame is received, the MTU value of the reception port is acquired and stored in the storage unit 41, and the MTU values of all transmission ports are acquired. The values are stored in the storage unit 42, and the values stored in the storage units 41 and 42 are compared by the comparator 43. The determination unit 44 transmits the multicast frame as it is to the transmission side port having the same or higher MTU value as the reception side port among the plurality of transmission side ports, and the MTU value is smaller than that of the reception side port. The transmission side port is instructed to the L2 bridge frame transfer processing unit 3 or the fragment processing unit 100 to perform the fragment processing on the multicast frame for transmission.

  FIG. 8 is a flowchart showing a procedure for processing a multicast frame by the bridge device according to the third embodiment of the present invention.

  First, the Ethernet multicast frame transmitted from the transmission source terminal is received by the bridge device 1 (step S301). At this time, the MAC address learning unit 2 performs MAC address learning based on, for example, IEEE 802.1D specifications.

  Next, the MTU value acquisition unit 51 acquires the MTU values of all ports including the port that has received the multicast frame (step S302). These MTU values are stored in the MTU holding unit 6. Note that acquisition of the MTU value is not necessarily performed after reception of the multicast frame, and the execution order of steps S301 and S302 may be switched.

  Next, the MTU value of the receiving port of the multicast frame is read from the MTU holding unit 6 and stored in the storage unit 41, and the MTU values of all other ports except the receiving port are similarly set in the MTU holding unit 6. Is stored in the storage unit 42. Here, the determination unit 44 determines whether there is a port having an MTU smaller than the port that has received the multicast frame (step S303). The comparator 43 compares the magnitudes of the MTU values stored in the storage units 41 and 42. Then, if there is no port having an MTU smaller than the reception port of the multicast frame, the determination unit 44 performs the L2 bridge frame transfer process so as to forward the multicast frame to all other ports except the reception port. The unit 3 is instructed (step S304).

  On the other hand, if it is determined in step S303 that there is a port having an MTU smaller than the multicast frame reception port, the MTU value is compared and determined for each of all ports except the multicast frame reception port. Thus, it is determined whether the multicast frame is to be fragmented for the port or forwarded as it is (step S305). That is, if the MTU value of the port is greater than or equal to the MTU value of the receiving port, the multicast frame is forwarded to the port as it is (step S306). On the other hand, if the MTU value of the port is not equal to or greater than the MTU value of the receiving port (step S305 = NO), the fragment processing unit 100 first determines the protocol type of the multicast frame (step S307). For example, if the source of the multicast frame uses IPv6 and is transmitting an IPv6 multicast frame, the fragment processing unit 100 performs IPv6 fragment processing on the multicast frame and sends it to the port (step S308). . On the other hand, when the transmission source uses IPv4, the fragment processing unit 100 performs IPv4 fragment processing on the multicast frame and sends it to the port (step S309). If the type of the multicast frame is neither IPv6 nor IPv4, the multicast frame is discarded and the process is terminated (step S310).

  As in this embodiment, by performing fragment processing on a multicast frame for a specific port based on the magnitude comparison of MTU values, it is possible to prevent frame discard due to MTU value mismatch.

(Fourth embodiment)
FIG. 9 is a block diagram showing a function expansion portion in the bridge device shown in FIG. 1 according to the fourth embodiment of the present invention. As shown in the figure, in addition to the components shown in FIG. 1, the bridge device 1 according to the present embodiment includes a multicast information learning unit 8, a multicast information holding unit 9, an MTU determination unit 40, and an MTU value acquisition. Unit 51, MTU holding unit 6, and fragment processing unit 100.

  The multicast information learning unit 8 learns multicast information based on the IGMP / MLD snoop function (reference URL <http://www.ietf.org/internet-drafts/draft-ietf-magma-snoop-10.txt>). To be held in the multicast information holding unit 9. According to the multicast information, it is possible to specify a port to which a multicast frame should be transferred toward terminals participating in the multicast group.

  The fragment processing unit 100 performs an appropriate fragment processing according to the procedure of PW fragmentation (reference URL <http://www.ietf.org/internet-drafts/draft-ietf-pwe3-fragmentation-05.txt>). IP fragment processing unit 101 and PW fragment processing unit 102 are provided.

  In FIG. 9, in the bridge device 1 of the present embodiment, substantially the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof will be given. Omitted.

  The MTU determination unit 40 reads the MTU (maximum transfer unit) value of the port that received the multicast frame from the MTU holding unit 6 and stores it, for example, by the storage unit 41 such as a register and the learning result by the multicast information learning unit 8 The MTU value of the transmission target port of the multicast frame to be transmitted is read from the MTU holding unit 6 and stored, for example, a storage unit 45 such as a register, and a comparator that compares the values of the storage unit 41 and the storage unit 45 ( COMP) 43 and a determination unit 44 that determines how to process the multicast frame according to the comparison result by the comparator 43. Specific processing contents of the determination unit 44 will be described later.

  As in the third embodiment, the bridge device 1 according to the present embodiment performs a fragment process on a specific port to transfer a multicast frame. The multicast address of the multicast frame and the multicast frame are The multicast information learning unit 8 learns multicast information that associates with a port to be transmitted, and the MTU is determined for a limited port based on the multicast information. This is different from the third embodiment.

  In the bridge device 1 of the present embodiment, when a multicast frame is received, the value of the MTU that the receiving port has is acquired and stored in the storage unit 41, and the multicast frame specified by the learning result by the multicast information learning unit 8 The MTU values of the transmission target ports are respectively acquired and stored in the storage unit 45, and both values stored in the storage units 41 and 45 are compared by the comparator 43. The determination unit 44 transmits the multicast frame as it is to the transmission side port having the same or higher MTU value as the reception side port among the plurality of transmission side ports, and the MTU value is smaller than that of the reception side port. The transmission side port is instructed to the L2 bridge frame transfer processing unit 3 or the fragment processing unit 100 to perform the fragment processing on the multicast frame for transmission.

  FIG. 9 is a flowchart showing a procedure for processing a multicast frame by the bridge device according to the fourth embodiment of the present invention.

  First, the Ethernet multicast frame transmitted from the transmission source terminal is received by the bridge device 1 (step S401). At this time, the MAC address learning unit 2 performs MAC address learning based on, for example, IEEE 802.1D specifications.

  Next, the multicast information learning unit 8 narrows down the transmission target (forwarding destination) port of the multicast frame by the IGMP / MLD snoop function (step S402).

  Next, the MTU value acquisition unit 51 acquires MTU values of all ports including the port that has received the multicast frame (step S403). These MTU values are stored in the MTU holding unit 6. Note that acquisition of the MTU value is not necessarily performed after reception of the multicast frame, and the execution order of steps S301 and S302 may be switched.

  Next, the MTU value of the receiving port of the multicast frame is read from the MTU holding unit 6 and stored in the storage unit 41, and the MTU value of the transfer destination port is similarly read from the MTU holding unit 6 and stored in the storage unit. 45. Here, the determination unit 44 determines whether there is a port having an MTU smaller than the port that has received the multicast frame (step S404). The comparator 43 compares the magnitudes of the MTU values stored in the storage units 41 and 45. Then, if there is no port having an MTU smaller than the reception port of the multicast frame, the determination unit 44 performs the L2 bridge frame transfer process so as to forward the multicast frame to all other ports except the reception port. The unit 3 is instructed (step S405).

  On the other hand, if it is determined in step S404 that there is a port having an MTU smaller than the receiving port of the multicast frame, the MTU value is compared and determined for each of the transfer destination ports, so that the multicast for that port is determined. It is determined whether the frame is to be fragmented or forwarded as it is (step S406). That is, if the MTU value of the port is greater than or equal to the MTU value of the receiving port, the multicast frame is forwarded to the port as it is (step S407). On the other hand, if the MTU value of the port is not equal to or greater than the MTU value of the receiving port (step S406 = NO), the fragment processing unit 100 first determines the protocol type of the multicast frame (step S408). For example, if the transmission source of the multicast frame uses IPv6 and is transmitting an IPv6 multicast frame, the fragment processing unit 100 performs IPv6 fragment processing on the multicast frame and sends it to the port (step S409). . On the other hand, when the transmission source uses IPv4, the fragment processing unit 100 performs IPv4 fragment processing on the multicast frame and sends it to the port (step S410). If the type of the multicast frame is not IPv6 or IPv4, the multicast frame is discarded and the process is terminated (step S411).

  According to the present embodiment, by discarding a multicast frame for a specific port in a port (forwarding destination port) narrowed down by the IGMP / MLD snoop function, frame discard due to mismatch of MTU values is prevented. it can.

(Fifth embodiment)
FIG. 11 is a block diagram showing a function expansion portion in the bridge device shown in FIG. 1 according to the fifth embodiment of the present invention. As shown in the figure, the bridge device 1 according to the present embodiment performs a unicast frame flooding process, and the L2 bridge frame transfer processing unit 3 includes an address resolution processing unit 31.

  The MTU determination unit 40 reads the MTU (maximum transfer unit) value of the port that received the unicast frame from the MTU holding unit 6 and stores it, for example, a storage unit 46 such as a register, and all ports other than this reception port That is, the MTU value of the flooding port is read from the MTU holding unit 6 and stored, for example, a storage unit 47 such as a register, and a comparator (COMP) that compares the values of the storage unit 46 and the storage unit 47 43 and a determination unit 44 that determines how to process the unicast frame according to the comparison result by the comparator 43. Specific processing contents of the determination unit 44 will be described later.

  In FIG. 11, in the bridge device 1 of the present embodiment, substantially the same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be given. Omitted.

  The bridge device 1 of the present embodiment addresses the problem of MTU mismatch when receiving a unicast frame and performing a flooding process.

  In the bridge device 1 of the present embodiment, when a unicast frame is received, the MTU value of the reception port is acquired and stored in the storage unit 46, and the MTUs of all transmission ports that are flooding targets are included. Each value is acquired and stored in the storage unit 47, and both of the values stored in the storage units 46 and 47 are compared by the comparator 43. The determination unit 44 determines whether any value of the MTU of the transmission side port is smaller than the value of the MTU of the reception side port, and if so, transmits the ICMP packet to the transmission source terminal. Instructs the ICMP packet transmission unit 52.

  FIG. 12 is a flowchart showing a procedure in which the bridge device according to the fifth embodiment of the present invention floods a unicast frame.

  First, the Ethernet unicast frame transmitted from the transmission source terminal is received by the bridge device 1 (step S501). At this time, the MAC address learning unit 2 performs MAC address learning based on, for example, IEEE 802.1D specifications.

  Next, the L2 bridge frame transfer processing unit 3 checks whether there is an entry in the forwarding database 32 for the port to which the received unicast frame is to be transferred. If there is an entry, the flooding process is unnecessary, and the unicast frame is transferred to the port specified by this entry, and the process ends (step S503).

  If there is no entry in the forwarding database 32, the MTU value acquisition unit 51 acquires the MTU value of the port that has received the unicast frame and the MTU values of all ports other than the reception port (step S504). These MTU values are stored in the MTU holding unit 6. Note that acquisition of the MTU value is not necessarily performed after reception of the unicast frame, and the execution order of steps S501 and S504 may be switched.

  Next, the MTU value of the receiving port of the unicast frame is read from the MTU holding unit 6 and stored in the storage unit 46, and the MTU values of all other ports are similarly read from the MTU holding unit 6. And stored in the storage unit 47. Here, the determination unit 44 determines whether there is a flooding target port having an MTU smaller than that of the port that has received the unicast frame (step S505). The comparator 43 compares the magnitudes of the MTU values stored in the storage units 46 and 47. If there is no port having an MTU smaller than the receiving port of the unicast frame, the unicast frame is flooded and the process ends (step S506).

  If there is a port having an MTU smaller than the receiving port of the unicast frame, the flooding process is prohibited (step S505 = YES). The ICMP packet transmission unit 52 acquires the IP address of the transmission source of the unicast frame from the IP transmission source / destination holding unit 7, and determines the protocol type of the unicast frame (step S507).

  For example, if the transmission source of the unicast frame uses IPv6 and is transmitting an IPv6 unicast frame, the ICMP packet transmission unit 52 transmits an ICMPv6 packet to this transmission source (step S508). Alternatively, when this transmission source uses IPv4, an ICMPv4 packet is transmitted to this transmission source (step S509). Note that it is preferable that these ICMP packets corresponding to the protocol type include the minimum value of the MTU of the transmission side port.

  After the ICMP packet is transmitted in step S508 or S509, the unicast frame is discarded and the current reception process is terminated (step S510).

  The transmission source that has received the notification by the ICMP packet can determine retransmission or the like by layer 3 processing of the ICMP packet. At the time of retransmission, it is possible to match the MTU for transmitting a unicast frame with the notified minimum value. Therefore, it is possible to appropriately cope with the problem of MTU mismatch when the unicast frame is transferred by the bridge device 1.

(Sixth embodiment)
FIG. 13 is a block diagram showing a function expansion portion in the bridge device shown in FIG. 1 according to the sixth embodiment of the present invention. As shown in the figure, the bridge device 1 according to the present embodiment performs a unicast frame flooding process, and the L2 bridge frame transfer processing unit 3 includes an address resolution processing unit 31.

  The MTU determination unit 40 reads the MTU (maximum transfer unit) value of the port that received the unicast frame from the MTU holding unit 6 and stores it, for example, a storage unit 46 such as a register, and all ports other than this reception port That is, the MTU value of the flooding port is read from the MTU holding unit 6 and stored, for example, a storage unit 47 such as a register, and a comparator (COMP) that compares the values of the storage unit 46 and the storage unit 47 43 and an address resolution processing control unit 48 for controlling the address resolution processing according to the comparison result by the comparator 43. Specific processing contents of the address resolution processing control unit 48 will be described later.

  In FIG. 13, in the bridge device 1 of this embodiment, substantially the same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be given. Omitted.

  The bridge device 1 according to the present embodiment addresses the problem of MTU mismatch when receiving a unicast frame and performing a flooding process, as in the fifth embodiment.

  In the bridge device 1 of the present embodiment, when a unicast frame is received, the MTU value of the reception port is acquired and stored in the storage unit 46, and the MTUs of all transmission ports that are flooding targets are included. Each value is acquired and stored in the storage unit 47, and both of the values stored in the storage units 46 and 47 are compared by the comparator 43. The address resolution processing control unit 48 prohibits the flooding process and sets the transmission source terminal as the transmission source if any of the MTU values of the transmission port to be flooded is smaller than the MTU value of the reception port. The address resolution processing unit 31 of the L2 bridge frame transfer processing unit 3 is controlled to execute the address resolution procedure. Then, the unicast frame is transmitted to the transfer destination resolved by the address resolution procedure of the address resolution processing unit 31.

  FIG. 14 is a flowchart showing a procedure for flooding a unicast frame by the bridge device according to the sixth embodiment of the present invention.

  First, the Ethernet unicast frame transmitted from the transmission source terminal is received by the bridge device 1 (step S601). At this time, the MAC address learning unit 2 performs MAC address learning based on, for example, IEEE 802.1D specifications.

  Next, the L2 bridge frame transfer processing unit 3 checks whether there is an entry in the forwarding database 32 for the port to which the received unicast frame is to be transferred (S602). If there is an entry, the flooding process is unnecessary, and the unicast frame is transferred to the port specified by this entry, and the process ends (step S603).

  If there is no entry in the forwarding database 32, the MTU value acquisition unit 51 acquires the MTU value of the port that has received the unicast frame and the MTU values of all ports other than the reception port (step S604). These MTU values are stored in the MTU holding unit 6. Note that acquisition of the MTU value is not necessarily performed after reception of the unicast frame, and the execution order of steps S601 and S604 may be switched.

  Next, the MTU value of the receiving port of the unicast frame is read from the MTU holding unit 6 and stored in the storage unit 46, and the MTU values of all other ports are similarly read from the MTU holding unit 6. And stored in the storage unit 47. Here, the determination unit 44 determines whether there is a flooding target port having an MTU smaller than that of the port that has received the unicast frame (step S605). The comparator 43 compares the magnitudes of the MTU values stored in the storage units 46 and 47. If there is no port having an MTU smaller than the receiving port of the unicast frame, the unicast frame is flooded and the process ends (step S606).

  If there is a port having an MTU smaller than the receiving port of the unicast frame, the flooding process is prohibited (step S605 = YES).

  Here, the address resolution processing control unit 48 determines the protocol type of the received unicast frame (step S607). For example, if the transmission source of the unicast frame uses IPv6 and is transmitting an IPv6 unicast frame, the address resolution processing control unit 48 sets the ND (specified in RFC 2461 to the address resolution processing unit 31. It is instructed to transmit a Neighbor Discovery) packet to all ports (step S608). Alternatively, when the transmission source uses IPv4, the address resolution processing control unit 48 transmits an ARP (Address Resolution Protocol) request packet defined in RFC826 to the address resolution processing unit 31 to all ports. (Step S609).

  After transmitting the ND packet or the ARP request packet in step S608 or S609, it waits for a predetermined time (step S610), and again refers to the forwarding database 32 to check whether there is an entry (step S611). If there is an entry, a unicast frame is transmitted to the port (step S613). If there is no entry, the unicast frame is discarded (step S612) and the process ends.

  In this embodiment, there is a possibility that the received unicast frame can be transmitted without flooding by the address resolution processing after the MTU determination. If the address cannot be resolved and the MTU does not match, flooding can be appropriately prohibited. .

(Seventh embodiment)
FIG. 15 is a block diagram showing a function expansion portion in the bridge device shown in FIG. 1 according to the seventh embodiment of the present invention. As shown in the figure, the bridge device 1 according to the present embodiment performs a unicast frame flooding process, and the L2 bridge frame transfer processing unit 3 includes an address resolution processing unit 31. In addition, a fragment processing unit 100 is provided. The fragment processing unit 100 follows the procedure of the IP protocol version and PW fragmentation (reference URL <http://www.ietf.org/internet-drafts/draft-ietf-pwe3-fragmentation-05.txt>). In addition, an IP fragment processing unit 101 and a PW fragment processing unit 102 are provided for performing appropriate fragment processing.

  The MTU determination unit 40 reads the MTU (maximum transfer unit) value of the port that received the unicast frame from the MTU holding unit 6 and stores it, for example, a storage unit 46 such as a register, and all ports other than this reception port That is, the MTU value of the flooding port is read from the MTU holding unit 6 and stored, for example, a storage unit 47 such as a register, and a comparator (COMP) that compares the values of the storage unit 46 and the storage unit 47 43, a comparator (COMP) 43 that compares the values of the storage unit 46 and the storage unit 47, and how to process the unicast frame according to the comparison result by the comparator 43 And a determination unit 44. Specific processing contents of the determination unit 44 will be described later.

  In FIG. 15, in the bridge device 1 of this embodiment, the same reference numerals as those in the first embodiment are assigned to components that are substantially the same as those in the first embodiment. Omitted.

  The bridge device 1 according to the present embodiment addresses the problem of MTU mismatch when receiving a unicast frame and performing a flooding process, as in the fifth embodiment.

  In the bridge device 1 of the present embodiment, when a unicast frame is received, the MTU value of the reception port is acquired and stored in the storage unit 46, and the MTUs of all transmission ports that are flooding targets are included. Each value is acquired and stored in the storage unit 47, and both of the values stored in the storage units 46 and 47 are compared by the comparator 43. The determination unit 44 determines whether or not the minimum value of the MTU of the transmission side port is smaller than the value of the MTU of the reception side port, and performs fragment processing for such a port.

  FIG. 16 is a flowchart showing a procedure in which the bridge device according to the seventh embodiment of the present invention floods a unicast frame.

  First, the Ethernet unicast frame transmitted from the transmission source terminal is received by the bridge device 1 (step S701). At this time, the MAC address learning unit 2 performs MAC address learning based on, for example, IEEE 802.1D specifications.

  Next, the L2 bridge frame transfer processing unit 3 checks whether there is an entry in the forwarding database 32 for the port to which the received unicast frame is to be transferred (S702). If there is an entry, the flooding process is unnecessary, and the unicast frame is transferred to the port specified by this entry, and the process ends (step S703).

  When there is no entry in the forwarding database 32, the MTU value acquisition unit 51 acquires the MTU value of the port that has received the unicast frame and the MTU values of all ports other than the reception port (step S704). These MTU values are stored in the MTU holding unit 6. Note that acquisition of the MTU value is not necessarily performed after reception of the unicast frame, and the execution order of steps S701 and S704 may be switched.

  Next, the MTU value of the receiving port of the unicast frame is read from the MTU holding unit 6 and stored in the storage unit 46, and the MTU values of all other ports are similarly read from the MTU holding unit 6. And stored in the storage unit 47. Here, the determination unit 44 determines whether there is a flooding target port having an MTU smaller than that of the port that has received the unicast frame (step S705). The comparator 43 compares the magnitudes of the MTU values stored in the storage units 46 and 47. If there is no port having an MTU smaller than the receiving port of the unicast frame, the unicast frame is flooded and the process ends (step S706).

  If there is a port having an MTU smaller than the receiving port of the unicast frame, the frame is subjected to fragment processing for such a port (step S705 = YES).

  By comparing and determining the value of the MTU for each of all ports except the receiving port of the unicast frame, it is determined whether the unicast frame is to be fragmented or forwarded as it is (step S707). ). That is, if the MTU value of the port is greater than or equal to the MTU value of the receiving port, the unicast frame is forwarded to the port as it is (step S708). On the other hand, if the MTU value of the port is not equal to or greater than the MTU value of the receiving port (step S707 = NO), the fragment processing unit 100 first determines the protocol type of the unicast frame (step S709). For example, if the transmission source of the unicast frame uses IPv6 and is transmitting an IPv6 unicast frame, the fragment processing unit 100 performs the IPv6 fragment processing on the unicast frame and sends it to the port ( Step S710). On the other hand, when the transmission source uses IPv4, the fragment processing unit 100 performs the fragment processing of IPv4 on the unicast frame and sends it to the port (step S711). If the type of unicast frame is neither IPv6 nor IPv4, the unicast frame is discarded and the process ends (step S712).

  As in this embodiment, by performing unicast frame fragment processing on a specific port based on the magnitude comparison of MTU values, it is possible to prevent frame discard due to mismatch of MTU values.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The figure which shows the network with which the bridge apparatus which concerns on embodiment of this invention was applied. The block diagram which shows the principal part of the bridge apparatus which concerns on 1st embodiment of this invention. The figure which shows an example of the packet format in the case of emulating L2 The flowchart which shows the procedure in which the bridge | bridging apparatus which concerns on 1st embodiment of this invention processes a multicast frame. The block diagram which shows the principal part of the bridge apparatus which concerns on 2nd embodiment of this invention. The flowchart which shows the procedure in which the bridge | bridging apparatus which concerns on 2nd embodiment of this invention processes a multicast frame. The block diagram which shows the principal part of the bridge apparatus which concerns on 3rd embodiment of this invention. The flowchart which shows the procedure in which the bridge | bridging apparatus which concerns on 3rd embodiment of this invention processes a multicast frame. The block diagram which shows the principal part of the bridge | bridging apparatus which concerns on 4th embodiment of this invention. The flowchart which shows the procedure in which the bridge | bridging apparatus which concerns on 4th embodiment of this invention processes a multicast frame. The block diagram which shows the principal part of the bridge | bridging apparatus which concerns on 5th embodiment of this invention. The flowchart which shows the procedure in which the bridge | bridging apparatus which concerns on 5th embodiment of this invention performs the flooding process of a unicast frame. The block diagram which shows the principal part of the bridge | bridging apparatus which concerns on 6th embodiment of this invention. The flowchart which shows the procedure in which the bridge | bridging apparatus based on 6th Embodiment of this invention performs the flooding process of a unicast frame. The block diagram which shows the principal part of the bridge apparatus which concerns on 7th embodiment of this invention. The flowchart which shows the procedure in which the bridge | bridging apparatus which concerns on 7th embodiment of this invention performs the flooding process of a unicast frame.

Explanation of symbols

1 ... Bridge device (L2 bridge);
2 ... MAC address learning unit;
3 ... L2 bridge frame transfer processing unit;
40 ... MTU determination unit;
50: ICMP processing section;
51 ... MTU value acquisition unit;
52 ... ICMP packet transmission unit;
6 ... MTU holding part;
7: IP transmission source / destination holding unit

Claims (14)

In a bridge device that receives a multicast frame from a transmission source terminal through a reception side network interface and transmits the multicast frame to a plurality of transmission side network interfaces.
Means for obtaining a value of a first maximum transfer unit possessed by the receiving side network interface and obtaining a value of a plurality of second maximum forwarding units possessed by the plurality of sending side network interfaces;
If the minimum value of the plurality of second maximum transfer units is smaller than the value of the first maximum transfer unit, an ICMP packet including the minimum value of the maximum transfer unit is sent to the source terminal. A bridge device comprising means for transmitting. In a bridge device that receives a multicast frame from a transmission source terminal through a reception side network interface and transmits the multicast frame to a plurality of transmission side network interfaces.
Means for storing multicast information associating a multicast address of the multicast frame with a transmission side network interface to which the multicast frame is to be transmitted;
Means for obtaining a value of a first maximum transfer unit possessed by the receiving network interface and obtaining a value of a plurality of second maximum forwarding units possessed by a plurality of transmitting network interfaces specified based on the multicast information When,
If the minimum value of the plurality of second maximum transfer units is smaller than the value of the first maximum transfer unit, an ICMP packet including the minimum value of the maximum transfer unit is sent to the source terminal. A bridge device comprising means for transmitting. In a bridge device that receives a multicast frame from a transmission source terminal through a reception side network interface and transmits the multicast frame to a plurality of transmission side network interfaces.
Means for obtaining a value of a first maximum transfer unit possessed by the receiving network interface and obtaining a value of a plurality of maximum transfer units possessed by the plurality of sending network interfaces;
In the plurality of transmission side network interfaces, the multicast frame is transmitted as it is to the transmission side network interface having a value of the maximum transfer unit equal to or greater than the first maximum transfer unit, and the first maximum A bridge device comprising: means for performing a fragment process on the multicast frame and transmitting it to a transmission-side network interface having a maximum transfer unit value smaller than that of the transfer unit. In a bridge device that receives a multicast frame from a transmission source terminal through a reception side network interface and transmits the multicast frame to a plurality of transmission side network interfaces.
Means for storing multicast information associating a multicast address of the multicast frame with a transmission side network interface to which the multicast frame is to be transmitted;
Means for obtaining a value of a first maximum transfer unit possessed by the receiving network interface and obtaining a value of a plurality of second maximum forwarding units possessed by a plurality of transmitting network interfaces specified based on the multicast information When,
In the plurality of transmission side network interfaces specified based on the multicast information, the multicast frame is left as it is for the transmission side network interface having the same value as or greater than the first maximum transfer unit. A bridge device comprising: means for transmitting and performing fragment processing on the multicast frame for transmission to a transmission-side network interface having a maximum transfer unit value smaller than the first maximum transfer unit. When a unicast frame is received from a transmission source terminal by a reception side network interface, if the transfer destination of the unicast frame is unresolved, a flooding process for transmitting the unicast frame to a plurality of transmission side network interfaces is performed. In the bridge device,
Means for obtaining a value of a first maximum transfer unit possessed by the receiving side network interface and obtaining a value of a plurality of second maximum forwarding units possessed by the plurality of sending side network interfaces;
If any of the values of the plurality of second maximum transfer units is smaller than the value of the first maximum transfer unit, the flooding process is prohibited and an ICMP packet is transmitted to the source terminal. And a bridge device. When a unicast frame is received from a transmission source terminal by a reception side network interface, if the transfer destination of the unicast frame is unresolved, a flooding process for transmitting the unicast frame to a plurality of transmission side network interfaces is performed. In the bridge device,
Means for obtaining a value of a first maximum transfer unit possessed by the receiving side network interface and obtaining a value of a plurality of second maximum forwarding units possessed by the plurality of sending side network interfaces;
If any of the values of the plurality of second maximum transfer units is smaller than the value of the first maximum transfer unit, the flooding process is prohibited and the address resolution with the source terminal as the source is performed. Means for performing the procedure;
A bridge device comprising: means for transmitting the unicast frame to a transfer destination resolved by the address resolution procedure. When a unicast frame is received from a transmission source terminal by a reception side network interface, if the transfer destination of the unicast frame is unresolved, a flooding process for transmitting the unicast frame to a plurality of transmission side network interfaces is performed. In the bridge device,
Means for obtaining a value of a first maximum transfer unit possessed by the receiving network interface and obtaining a value of a plurality of maximum transfer units possessed by the plurality of sending network interfaces;
In the plurality of transmission side network interfaces, the unicast frame is transmitted as it is to the transmission side network interface having a value of the maximum transfer unit equal to or greater than the first maximum transfer unit, and the first A bridge device comprising: means for performing a fragment process on the unicast frame and transmitting it to a transmission side network interface having a maximum transfer unit value smaller than the maximum transfer unit. In a control method of a bridge device that receives a multicast frame from a transmission source terminal via a reception side network interface and transmits the multicast frame to a plurality of transmission side network interfaces.
Obtaining a value of a first maximum transfer unit possessed by the receiving network interface and obtaining a value of a plurality of second maximum transfer units possessed by the plurality of transmitting network interfaces;
If the minimum value of the plurality of second maximum transfer units is smaller than the value of the first maximum transfer unit, an ICMP packet including the minimum value of the maximum transfer unit is sent to the source terminal. And a step of transmitting the bridge device. In a control method of a bridge device that receives a multicast frame from a transmission source terminal via a reception side network interface and transmits the multicast frame to a plurality of transmission side network interfaces.
Storing multicast information associating a multicast address of the multicast frame with a transmission side network interface to which the multicast frame is to be transmitted;
Obtaining a value of a first maximum transfer unit possessed by the receiving-side network interface and obtaining a value of a plurality of second maximum forwarding units possessed by a plurality of transmitting-side network interfaces specified based on the multicast information When,
If the minimum value of the plurality of second maximum transfer units is smaller than the value of the first maximum transfer unit, an ICMP packet including the minimum value of the maximum transfer unit is sent to the source terminal. And a step of transmitting the bridge device. In a control method of a bridge device that receives a multicast frame from a transmission source terminal via a reception side network interface and transmits the multicast frame to a plurality of transmission side network interfaces.
Obtaining values of a first maximum transfer unit possessed by the receiving network interface and obtaining values of a plurality of maximum transfer units possessed by the plurality of transmitting network interfaces;
In the plurality of transmission side network interfaces, the multicast frame is transmitted as it is to the transmission side network interface having a value of the maximum transfer unit equal to or greater than the first maximum transfer unit, and the first maximum And a step of performing fragment processing on the multicast frame and transmitting it to a transmission side network interface having a maximum transfer unit value smaller than that of the transfer unit. In a control method of a bridge device that receives a multicast frame from a transmission source terminal via a reception side network interface and transmits the multicast frame to a plurality of transmission side network interfaces.
Storing multicast information associating a multicast address of the multicast frame with a transmission side network interface to which the multicast frame is to be transmitted;
Obtaining a value of a first maximum transfer unit possessed by the receiving-side network interface and obtaining a value of a plurality of second maximum forwarding units possessed by a plurality of transmitting-side network interfaces specified based on the multicast information When,
In the plurality of transmission side network interfaces specified based on the multicast information, the multicast frame is left as it is for the transmission side network interface having the same value as or greater than the first maximum transfer unit. And a step of transmitting the multicast frame by performing fragment processing on a transmission-side network interface having a maximum transfer unit value smaller than that of the first maximum transfer unit. When a unicast frame is received from a transmission source terminal by a reception side network interface, if the transfer destination of the unicast frame is unresolved, a flooding process for transmitting the unicast frame to a plurality of transmission side network interfaces is performed. In the control method of the bridge device,
Obtaining a value of a first maximum transfer unit possessed by the receiving network interface and obtaining a value of a plurality of second maximum transfer units possessed by the plurality of transmitting network interfaces;
If any of the values of the plurality of second maximum transfer units is smaller than the value of the first maximum transfer unit, the flooding process is prohibited and an ICMP packet is transmitted to the source terminal. And a step of controlling the bridge device. When a unicast frame is received from a transmission source terminal by a reception side network interface, if the transfer destination of the unicast frame is unresolved, a flooding process for transmitting the unicast frame to a plurality of transmission side network interfaces is performed. In the control method of the bridge device,
Obtaining a value of a first maximum transfer unit possessed by the receiving network interface and obtaining a value of a plurality of second maximum transfer units possessed by the plurality of transmitting network interfaces;
If any of the values of the plurality of second maximum transfer units is smaller than the value of the first maximum transfer unit, the flooding process is prohibited and the address resolution with the source terminal as the source is performed. Steps to perform the procedure;
And a step of transmitting the unicast frame to a transfer destination resolved by the address resolution procedure. When a unicast frame is received from a transmission source terminal by a reception side network interface, if the transfer destination of the unicast frame is unresolved, a flooding process for transmitting the unicast frame to a plurality of transmission side network interfaces is performed. In the control method of the bridge device,
Obtaining values of a first maximum transfer unit possessed by the receiving network interface and obtaining values of a plurality of maximum transfer units possessed by the plurality of transmitting network interfaces;
In the plurality of transmission side network interfaces, the unicast frame is transmitted as it is to the transmission side network interface having a value of the maximum transfer unit equal to or greater than the first maximum transfer unit, and the first And a step of performing fragment processing on the unicast frame and transmitting the transmission side network interface having a smaller value of the maximum transfer unit than the maximum transfer unit.

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